Work-related physical and psychosocial risk factors for sick leave in patients with neck or upper extremity complaints Objectives To study work-related physical and psychosocial risk factors for sick leave among patients who have visited their general practitioner for neck or upper extremity complaints . Introduction Many people suffer from work-related neck and upper extremity complaints . In a population-based study in the Netherlands , the 12-month prevalence of work-related neck and upper extremity symptoms was found to be 31 % -LRB- Blatter and Bongers 1999 -RRB- . These complaints have an important impact on loss of time from work . Sick leave has enormous cost implications , considering costs to employers , insurers , health care providers , and patients themselves . In the Netherlands , 8 % of the employed population reported lost days from work in the past year because of complaints at the neck , shoulder , arm , elbow , wrist or hand -LRB- Blatter et al. 2001 -RRB- . The results of a British national survey in 1995 showed that musculoskeletal disorders of the neck and upper extremity were responsible for the loss of 4.2 million working days in a 12-month period -LRB- Jones et al. 1998 -RRB- . Borghouts et al. -LRB- 1999 -RRB- estimated the total number of sick days due to neck pain in 1996 in the Netherlands to be 1.4 million , with a total cost of US$ 185.4 million . It is well recognized that neck and upper extremity complaints have a multi-factorial aetiology . Several reviews have identified individual characteristics , and -LRB- work-related -RRB- physical and psychosocial factors as risk factors for the onset of neck and upper extremity complaints -LRB- Bernard 1997 ; Bongers et al. 2002a , b ; Malchaire et al. 2001 ; Muggleton et al. 1999 ; van der Windt et al. 2000 ; Zakaria et al 2002 -RRB- . Furthermore , these factors have also been recognized as potential prognostic factors for chronic pain and disability in patients with neck or upper extremity complaints -LRB- Ariëns et al. 2000 , 2001 ; Cole and Hudak 1996 ; Eriksen et al. 1999 ; Feuerstein et al. 2000 -RRB- . However , relatively little is known about the association of work-related factors with sick leave in patients with neck or upper extremity complaints . Risk factors for the onset of neck and upper extremity complaints may differ from risk factors for sick leave due to these complaints -LRB- IJzelenberg et al. 2004 -RRB- . Ekberg and Wildhagen -LRB- 1996 -RRB- studied the impact of physical workload , work organization , psychosocial conditions and individual characteristics on days of sick leave after rehabilitation in patients with neck and shoulder disorders . They found two work-related factors -LRB- i.e. , work content and uncomfortable sitting -RRB- to be independently related to sick leave days . A prospective cohort study on work-related determinants of sick leave in employees without neck pain at baseline suggested that work-related neck flexion and rotation , sitting , decision authority and skill discretion were independently related to sick leave due to neck pain -LRB- Ariëns et al. 2002 -RRB- . In contrast to these findings , a recent cross-sectional study on risk factors for musculoskeletal sick leave showed that physical workload nor psychosocial workload were significantly related to sick leave due to neck or upper extremity pain -LRB- IJzelenberg et al. 2004 -RRB- . Hansson and Jensen -LRB- 2004 -RRB- reviewed the literature on the causes for back and neck disorders and found that heavy physical workload , bent or twisted working position and low work satisfaction increased the risk of short-term and long-term sick leave , and self-reported pain and functional impairments were associated with a high risk for long-term sick leave . Exposure to work-related physical risk factors may lead to pain and disability , which in turn may lead to sick leave . Psychosocial exposures at work may lead to psychological distress that may cause physiologic changes in the neck and upper extremity -LRB- e.g. , increased muscle tension -LRB- Hagg and Astrom 1997 ; Lundberg 2002 ; Rissen et al. 2000 -RRB- , causing pain and disability , which in turn may lead to sick leave . Furthermore , psychosocial exposures at work may modify the effect of physical workload on sick leave . The objective of our study was to determine the influence of work-related physical and psychosocial risk factors on sick leave due to neck or upper extremity complaints in patients who have visited their general practitioner -LRB- GP -RRB- for these complaints . Methods Design and study population This study is part of a large observational cohort study on musculoskeletal disorders conducted in 61 general practices -LRB- 97 GPs -RRB- -LRB- van der Waal et al. 2003 -RRB- . Part of the GPs participated in the second Dutch National Survey of General Practice -LRB- NS2 -RRB- , carried out by the Netherlands Institute for Health Services Research in co-operation with the National Information Network of General Practice in 2001 -LRB- Schellevis et al. 2003 -RRB- . The Medical Ethics Committee of the VU University Medical Center approved our study . Written informed consent was obtained from all patients . Details of the study design are described elsewhere -LRB- van der Waal et al 2003 -RRB- . Over a period of 1 year the GPs recruited 727 patients with a new complaint or new episode of a complaint at the neck , shoulder , elbow , arm , wrist or hand . An episode was considered to be ` new ' if patients had not visited their GP for the same complaint during the preceding 3 months . Patients were eligible for participation if they were 18 years or older and capable of filling in Dutch questionnaires . Patients were excluded from the study if the presented symptoms were presumably caused by a fracture , malignancy , prosthesis , amputation or congenital defect or if the patient was pregnant . At baseline a self-report questionnaire was sent to collect data on a broad range of factors -LRB- including work-related factors -RRB- that may be predictive of sick leave . In total , 643 patients -LRB- 88 % -RRB- returned the baseline questionnaire , of whom five patients were excluded -LRB- two were too young ; three were pregnant -RRB- . For our study , patients who reported to have paid work for more than 8 h per week were included -LRB- 8 -- 16 h : n = 41 ; 17 -- 24 h : n = 69 ; 25 -- 36 h : n = 101 ; > 36 h : n = 172 -RRB- . Outcome -LRB- sick leave due to neck and/or upper extremity complaints -RRB- was assessed after 3 months using a self-report questionnaire . Outcome measure Sick leave was measured at 3 months after baseline by the question : `` how long were you absent from work because of your complaint since the baseline questionnaire '' . Response categories were -LRB- 1 -RRB- no sick leave ; -LRB- 2 -RRB- less than 1 week ; -LRB- 3 -RRB- between 1 and 2 weeks ; -LRB- 4 -RRB- between 2 weeks and 1 month ; -LRB- 5 -RRB- between 1 and 3 months ; -LRB- 6 -RRB- more than 3 months . Sick leave was dichotomised into no sick leave -LRB- response category 1 -RRB- and sick leave -LRB- response categories 2 -- 6 -RRB- . Determinants At baseline , work-related physical risk factors were assessed by a questionnaire consisting of two scales `` heavy physical workload '' -LSB- 12 items ; e.g. , does your work involve -LRB- a -RRB- standing for long periods of time , -LRB- b -RRB- walking for long periods of time , -LRB- c -RRB- moving loads , -LRB- d -RRB- physical hard work -RSB- and `` long-lasting postures and repetitive movements '' -LSB- six items ; e.g. , does your work involve -LRB- a -RRB- making the same movement for long periods of time ; -LRB- b -RRB- bending or twisting your neck often ; -LRB- c -RRB- working in the same position for long periods of time ; -LRB- d -RRB- doing repetitive tasks with arms , hands or fingers many times per minute -RRB- -LRB- Bot et al. 2004 -RRB- . Response options varied from `` seldom or never '' , `` sometimes '' , `` often '' , and `` -LRB- almost -RRB- always '' . Scoring was done by simply adding up the response to each item , which produced a raw score from 0 to 36 for the first subscale , and 0 to 18 for the second subscale . The final scores were calculated by dividing the raw score by the maximum score , multiplied by 100 , resulting in a final score ranging between 0 -LRB- no workload -RRB- and 100 -LRB- highest workload -RRB- for both subscales . The internal consistency and validity of this questionnaire were considered to be good in a population with upper extremity and lower extremity musculoskeletal disorders -LRB- Bot et al. 2004 -RRB- . Furthermore , two questions about `` prolonged sitting '' and `` working with visual display units -LRB- VDU -RRB- for long periods of time '' -LRB- yes/no -RRB- were asked . Work-related psychosocial risk factors were assessed according to the Demands -- Control model of Karasek -LRB- 1979 -RRB- . We used three subscales of the Job Content Questionnaire -LRB- JCQ -RRB- : `` job demands '' , `` decision authority '' and `` co-worker support '' and one single item on `` job security '' -LRB- Karasek et al. 1998 -RRB- . The hypothesis of the Demands -- Control model is that the most adverse reactions of psychological strain occur when demands are high and the worker 's decision latitude is low -LRB- Karasek et al. 1998 -RRB- . Therefore , we decided to combine the subscales high job demands and low decision authority into an additional determinant `` job strain '' . Both subscales were dichotomized by their median score and four categories were created : -LRB- 1 -RRB- high decision authority and low job demands -LRB- reference category -RRB- ; -LRB- 2 -RRB- high decision authority and high job demands ; -LRB- 3 -RRB- low decision authority and low job demands ; -LRB- 4 -RRB- low decision authority and high job demands . Statistical analysis Descriptive statistics -LRB- e.g. , means and standard deviations -RRB- were used to present baseline characteristics of the study population . Differences between patients reporting sick leave and patients without sick leave were tested with the unpaired Student T-test -LRB- continuous variables -RRB- and the Chi square -LRB- χ2 -RRB- test -LRB- categorical and dichotomous variables -RRB- . In case a continuous variable was not normally distributed the Mann -- Whitney test was used . Instead of using logistic regression analysis , Cox regression models with equal survival time were used to investigate the association between work-related risk factors -LRB- determinants -RRB- and sick leave -LRB- outcome -RRB- . Hazard ratios are more easy to interpret and provide a better estimate of relative risks than odds ratios -LRB- Barros and Hirakata 2003 ; Lee and Chia 1994 ; Skov et al. 1998 ; Thompson et al. 1998 -RRB- Associations were expressed as hazard ratios -LRB- HR -RRB- and corresponding 95 % confidence intervals -LRB- 95 % CI -RRB- per unit increase of the risk factor involved . For continuous factors the linearity of the relation between the risk factor and sick leave was examined . Factors that were found to be non-linearly related to sick leave were either dichotomized or divided into tertiles with equally sized groups -LRB- Table 1 -RRB- . The `` low-category '' served as the reference category in all analyses . Table 1Potential confounders of the association between work-related risk factors and sick leave in patients with neck or upper extremity complaintsPotential confoundersCategorizationIndividual factors AgeContinuous -LRB- per year -RRB- SexMale versus female SmokingPresent versus previous smoker EducationPrimary versus secondary ; college/university Pain copinga : retreating -LRB- seven items -RRB- Continuous -LRB- scale 7 -- 28 -RRB- Pain copinga : worrying -LRB- nine items -RRB- Continuous -LRB- scale 9 -- 36 -RRB- Distress -LRB- six items -RRB- Continuous -LRB- scale 1 -- 9 -RRB- General health ACSM position standcNorm not met versus norm met Norm healthy activityNorm not met versus norm met Perceived healthdContinuous -LRB- scale 1 -- 5 -RRB- Vitalityd -LRB- four items -RRB- Continuous -LRB- scale 0 -- 100 -RRB- Quality of lifeContinuous -LRB- scale 1 -- 5 -RRB- Characteristics of the complaint Kind of complaintLocalized versus generalized Duration of the complaintCategorical -LRB- < 1 , 1 -- 4 weeks ; 1 -- 6 , > 6 months -RRB- History of neck/upper limb complaintsHistory versus no history Musculoskeletal co-morbidityYes versus no Other co-morbidityYes versus noWork-related psychosocial factors -LRB- % -RRB- Decision authorityf -LRB- three items -RRB- Tertiles -LRB- low , medium , high -RRB- Job demandsf -LRB- five items -RRB- Tertiles -LRB- low , medium , high -RRB- Co-worker supportf -LRB- four items -RRB- Tertiles -LRB- low , medium , high -RRB- Job-securityfLow security versus high security Job as perceived cause of complaintYes versus noaPain Coping Inventory -LRB- Kraaimaat and Evers 2003 ; Kraaimaat et al. 1997 -RRB- bFour Dimensional Symptom Questionnaire -LRB- Terluin 1998 -RRB- cAmerican College of Sports Medicine Position Stand -LRB- American College of Sports Medicine Position Stand 1990 -RRB- dMedical Outcomes Study 36-item Short Form Health Survey -LRB- Ware and Sherbourne 1992 -RRB- ePhysical workload questionnaire -LRB- Bot et al. 2004 -RRB- fJob Content Questionnaire -LRB- Karasek et al. 1998 -RRB- ; % work-related psychosocial factors were considered as potential confounders in the relation between work-related physical factors and sick leave To prevent multicollinearity we checked whether the psychosocial risk factors , the physical risk factors , and potential confounders were highly correlated -LRB- P > 0.5 or P < − 0.5 -RRB- . The factor with the highest association with sick leave was retained and the other factor was removed from further analyses . This was the case for prolonged sitting and prolonged VDU work -LRB- P = 0.69 -RRB- , distress and worrying -LRB- P = 0.52 -RRB- ; prolonged VDU-work and heavy physical work -LRB- P = − 0.56 -RRB- , and prolonged sitting and heavy physical work -LRB- P = − 0.65 -RRB- . We performed the analyses in several stages . First , the unadjusted relationships between the work-related risk factors and sick leave were examined . Second , these relationships were adjusted for each of the potential confounders individually . Potential confounders of the relationship between work-related risk factors and sick leave included individual factors , general health , characteristics of the complaint , and other work-related risk factors -LRB- Table 1 -RRB- . Factors were considered as potential confounders if they had been reported as predictive of sick leave or poor prognosis in previously published scientific papers . Only those factors that led to a considerable change in the regression coefficient of the risk factor -LRB- > 10 % -RRB- were considered as potential confounders in the multiple regression models . Next , a manual forward selection procedure was used to sequentially include potential confounders that induced the most change in the regression coefficient of the risk factor -LRB- i.e. , in order of highest change of the regression coefficient -RRB- . Confounders that changed the regression coefficient of sick leave by more than 10 % were retained in the model . If the unadjusted relationship between the work-related risk factor and sick leave was not statistically significant -LRB- P > 0.05 -RRB- and remained not significant after controlling for all potential confounders individually , the relationship was adjusted for sick leave at baseline and sex only . Individual factors may interact in the relation between work-related physical and psychosocial risk factors and sick leave . We considered possible effect modification by sick leave at baseline , sex , coping style worrying -LRB- dichotomized -RRB- and musculoskeletal co-morbidity . Product terms of the potential effect modifier and the work-related risk factor were added to the model -LRB- e.g. , sex × risk factor -RRB- . Furthermore , possible effect modification by psychosocial risk factors was investigated in the relation between the four physical risk factors and sick leave . Factors significantly interacting with determinants in the model were retained in the models . In case of significant effect modification stratified analyses were carried out presenting the effect of the work-related risk factor for relevant subgroups of workers . All analyses were performed with the use of SPSS for Windows version 10.1 -LRB- SPSS Inc. , Chicago , IL , USA -RRB- . Results In total , 342 of the 383 included patients -LRB- 89 % -RRB- completed the 3 months follow-up questionnaire . Fifty-eight of the patients were excluded , because data on sick leave at follow-up were missing . There were no significant differences between responders and dropouts by age , sex , and any of the determinants -LRB- P > 0.05 -RRB- . Baseline characteristics of patients reporting sick leave in the 3 months following baseline -LRB- n = 73 -RRB- and patients without sick leave -LRB- n = 252 -RRB- are shown in Table 2 . The mean age of the total study population was 43 years -LRB- SD 10.3 -RRB- and 54 % was female . At baseline 80 patients reported sick leave in the 3 months preceding baseline due to their neck or upper extremity complaint . Half of these patients reported sick leave in the 3 months following baseline . With reference to physical and psychosocial risk factors , there was a statistically significant difference between patients reporting sick leave and patients without sick leave for decision authority , heavy physical work , static postures and repetitive movements , prolonged sitting and prolonged VDU-work . Table 2Baseline characteristics and values of patients with neck or upper extremity complaints reporting sick leave -LRB- n = 73 -RRB- and of patients reporting no sick leave -LRB- n = 252 -RRB- due to their complaints in the 3 months following baseline assessmentCharacteristicSick leaveaNo sick leaveaTotalIndividual factors Age , years -LSB- mean -LRB- SD -RRB- -RSB- 42.0 -LRB- 11.5 -RRB- 43.6 -LRB- 9.8 -RRB- 43.0 -LRB- 10.3 -RRB- Sex -LRB- female -RRB- 75 % 49 % ** 54 % Sick leave in 3 months before baseline59 % 16 % ** 25 % Education level Primary48 % 30 % * 34 % Secondary40 % 49 % 48 % College/university12 % 21 % 18 % Number of hours work -LRB- h -RRB- 8 -- 1611 % 12 % 11 % 17 -- 2418 % 25 % 20 % 25 -- 3626 % 30 % 27 % > 3645 % 33 % 42 % Married/living together63 % 83 % * 78 % Smoking -LRB- now , ever -RRB- 77 % 67 % 70 % Pain coping : retreating -LSB- scale 7 -- 28 ; median -LRB- IR -RRB- -RSB- 11.0 -LRB- 5.0 -RRB- 9.0 -LRB- 4.8 -RRB- ** 10.0 -LRB- 4.5 -RRB- Pain coping : worrying -LRB- scale 9 -- 36 ; median -LRB- IR -RRB- -RRB- 18.0 -LRB- 7.0 -RRB- 14.0 -LRB- 5.0 -RRB- ** 15.0 -LRB- 6.0 -RRB- Psychological distress -LRB- scale 0 -- 12 ; median -LRB- IR -RRB- -RRB- 7.0 -LRB- 5.0 -RRB- 4.0 -LRB- 5.0 -RRB- ** 5.0 -LRB- 6.0 -RRB- General health Meeting ACSM position stand4 % 16 % * 13 % Meeting Norm Healthy Activity41 % 42 % 43 % Perceived health -LSB- scale 1 -- 5 ; mean -LRB- SD -RRB- -RSB- 3.1 -LRB- 0.8 -RRB- 3.4 -LRB- 0.9 -RRB- * 3.3 -LRB- 0.8 -RRB- Quality of life -LSB- scale 1 -- 5 ; mean -LRB- SD -RRB- -RSB- 3.2 -LRB- 0.7 -RRB- 3.5 -LRB- 0.8 -RRB- * 3.4 -LRB- 0.8 -RRB- Vitality -LSB- scale 0 -- 100 ; mean -LRB- SD -RRB- -RSB- 54.3 -LRB- 20.9 -RRB- 62.4 -LRB- 17.2 -RRB- ** 60.0 -LRB- 18.5 -RRB- Characteristics complaint Localized complaint40 % 53 % * 49 % Complaint at both arms10 % 15 % 13 % Complaint at dominant arm50 % 44 % 47 % Duration of current episode < 1 week5 % 7 % 7 % 1week -- 1 month36 % 32 % 33 % 1 -- 6 months29 % 37 % 34 % > 6 months30 % 24 % 26 % History of elbow complaints51 % 43 % 45 % Musculoskeletal co-morbidity56 % 47 % 50 % Pain intensity -LSB- scale 0 -- 10 ; mean , -LRB- SD -RRB- -RSB- 6.0 -LRB- 1.9 -RRB- 4.4 -LRB- 2.1 -RRB- ** 4.8 -LRB- 2.2 -RRB- Functional disability -LSB- scale 0 -- 100 ; median -LRB- IR -RRB- -RSB- 36.3 -LRB- 28.8 -RRB- 16.5 -LRB- 21.3 -RRB- ** 20.0 -LRB- 25.3 -RRB- Work-related factors Heavy physical work -LSB- scale 0 -- 100 ; mean -LRB- SD -RRB- -RSB- 36.1 -LRB- 40.2 -RRB- 16.7 -LRB- 36.1 -RRB- ** 22.2 -LRB- 42.8 -RRB- Static postures and repetitive movements -LRB- scale 0 -- 100 -RRB- 55.6 -LRB- 47.2 -RRB- 44.4 -LRB- 44.4 -RRB- ** 44.4 -LRB- 38.9 -RRB- Sitting for a long period of time22 % 48 % ** 42 % VDU-work for a long period of time21 % 36 % * 31 % Decision authority -LSB- scale 3 -- 12 ; mean -LRB- SD -RRB- -RSB- 9.0 -LRB- 3.0 -RRB- 9.0 -LRB- 3.0 -RRB- * 9.0 -LRB- 3.0 -RRB- Job demands -LSB- scale 5 -- 20 ; mean -LRB- SD -RRB- -RSB- 13.4 -LRB- 3.6 -RRB- 12.8 -LRB- 2.9 -RRB- 12.9 -LRB- 3.1 -RRB- Co-worker support -LSB- scale 4 -- 16 ; mean -LRB- SD -RRB- -RSB- 12.0 -LRB- 1.0 -RRB- 12.0 -LRB- 2.0 -RRB- 12.0 -LRB- 2.0 -RRB- Job security78 % 85 % 83 % Job as perceived cause of complaint62 % 49 % 56 % VDU visual display unit , SD standard deviation , IR interquartile range * P < 0.05 ; ** P < 0.001 -LRB- independent T-test , Mann -- Whitney test , or χ2-test -RRB- avalues are percentages of patients unless indicated Table 3 shows the effect of work-related physical and psychosocial risk factors on sick leave . After adjustment for confounders , a statistically significant effect was found for heavy physical work and prolonged sitting , but only in patients with a high score on pain coping strategy `` worrying '' . In patients who scored low on the pain coping subscale `` worrying '' the hazard ratio of sick leave was 1.05 -LRB- 0.93 -- 1.18 , P = 0.46 -RRB- per 10 % increase in heavy physical work . In patients scoring high on `` worrying '' the relative risk of sick leave was 1.32 -LRB- 95 % CI 1.07 -- 1.62 -RRB- per 10 % increase in heavy physical work . Patients who were sitting for long periods of time had a reduced risk of sick leave as compared to patients who did not spent a lot of time sitting , again only in patients who scored high on `` worrying '' -LRB- HR = 0.17 , 95 % CI 0.04 -- 0.72 -RRB- . In patients who scored low on `` worrying '' , sitting for long periods of time did not have an effect on sick leave -LRB- P = 0.43 -RRB- . Sick leave at baseline , sex and musculoskeletal co-morbidity did not modify the relationship between the physical and psychosocial risk factors and sick leave . The psychosocial risk factors neither modified the relationship between heavy physical work and sick leave . Table 3Relationship between work-related risk factors and sick leave in patients with neck or upper extremity complaints : results from the multiple Cox regression analysesDeterminantNCrude HR95 % CIAdjusted HR95 % CIHeavy physical work -LRB- per 10 % increase -RRB- 69/3201 .23 -LSB- 1.12 ; 1.36 -RSB- * For patients with low scores on worrying d21/1401 .05 -LSB- 0.93 ; 1.18 -RSB- a For patients with high scores on worryingd48/1801 .32 -LSB- 1.07 ; 1.62 -RSB- a , * Static postures , repetitive movements -LRB- per 10 % increase -RRB- 69/3201 .16 -LSB- 1.06 ; 1.27 -RSB- * 1.04 -LSB- 0.94 ; 1.14 -RSB- bSitting for long periods of time -LRB- vs. never/now and then -RRB- 16/3220 .40 -LSB- 0.23 ; 0.70 -RSB- * For patients with low scores on worryingd2/1800 .81 -LSB- 0.43 ; 1.52 -RSB- a For patients with high scores on worryingd14/1420 .17 -LSB- 0.04 ; 0.72 -RSB- a , * VDU-work long periods of time -LRB- vs. never/now and then -RRB- 15/3220 .56 -LSB- 0.32 ; 1.00 -RSB- * 0.70 -LSB- 0.36 ; 1.36 -RSB- cDecision authority Low1 .00 Medium0 .80 -LSB- 0.47 ; 1.35 -RSB- 0.94 -LSB- 0.55 ; 1.59 -RSB- a High0 .59 -LSB- 0.31 ; 1.13 -RSB- 0.87 -LSB- 0.45 ; 1.68 -RSB- aJob demands Low23/1151 .001.00 Medium20/1110 .90 -LSB- 0.49 ; 1.64 -RSB- 0.91 -LSB- 0.50 ; 1.66 -RSB- a High27/951 .42 -LSB- 0.81 ; 2.48 -RSB- 1.13 -LSB- 0.64 ; 1.97 -RSB- aCo-worker support Low16/861 .001.00 Medium31/1401 .19 -LSB- 0.65 ; 2.18 -RSB- 1.22 -LSB- 0.67 ; 2.23 -RSB- a High23/881 .40 -LSB- 0.74 ; 2.66 -RSB- 1.14 -LSB- 0.59 ; 2.17 -RSB- aLow job security -LRB- vs high -RRB- 70/3191 .43 -LSB- 0.78 ; 2.60 -RSB- 1.47 -LSB- 0.80 ; 2.69 -RSB- aJob strain High decision authority , low job demands10/771 .001.00 High decision authority , high job demands11/521 .63 -LSB- 0.69 ; 3.84 -RSB- 1.29 -LSB- 0.54 ; 3.07 -RSB- b Low decision authority , low job demands25/1041 .85 -LSB- 0.89 ; 3.85 -RSB- 1.30 -LSB- 0.62 ; 2.73 -RSB- b Low decision authority , high job demands 24/862 .15 -LSB- 1.03 ; 4.49 -RSB- * 1.15 -LSB- 0.54 ; 2.47 -RSB- bN Number of patients reporting sick leave/total , HR hazard ratio * P < 0.05 aAdjusted for sick leave at baseline and sexbAdjusted for sick leave at baseline , sex and worryingcAdjusted for sick leave at baseline , sex , education level , quality of life , working in static postures and with repetitive movementsdEffect modification by worrying Discussion We studied a population of working employees who consulted their GP with a complaint at the neck or upper extremity . The results show that heavy physical work and prolonged sitting in patients that worry a lot predicted sick leave in the three successive months after baseline . Other physical and psychosocial risk factors appeared not to be related to sick leave after adjustment for confounding variables . Individual factors and stress may have a modifying effect on the relation between work related factors and outcome in musculoskeletal complaints . The pain coping style `` worrying '' appeared to be an effect modifier in the relationship between heavy physical work and sick leave . An increase of 10 % of heavy physical work in patients who worried a lot increased the probability on sick leave with 1.3 . A passive coping style like worrying -LRB- e.g. , `` focus on pain all the time '' ; `` I think the pain will get worse '' -RRB- is thought to generate a preoccupation with bodily symptoms , which may increase the perception of pain and disability -LRB- Covic et al. 2000 ; Evers et al. 2003 -RRB- or generate a different appraisal of the work situation and musculoskeletal symptoms -LRB- Bongers et al. 2002b -RRB- , which in turn may lead to sick leave . Sitting for long periods of time reduced the risk of sick leave , only in patients who scored high on the pain subscale `` worrying '' In the study of Ariëns et al. -LRB- 2002 -RRB- sitting was also related to a reduced risk of sick leave . However , uncomfortable sitting has been found to increase the number of days on sick leave due to neck and shoulder disorders -LRB- Ekberg and Wildhagen 1996 -RRB- . Sitting was highly negatively correlated with heavy physical work . Perhaps , people who sit for long periods of time at their work do not experience heavy physical work , and thus the absence of heavy physical work results in a reduced risk . This may explain why sitting had only a protective effect in patients that worry a lot . In the unadjusted analyses , all the physical risk factors and two of the psychosocial risk factors -LRB- i.e. , decision authority and job strain -RRB- had a statistically significant effect on sick leave . It is partly due to the underlying distribution of the exposure which physical factors are most strongly associated with sick leave in the multivariate analyses . Adjustment for sick leave at baseline had the strongest effect on the presented associations , diminishing the strength of the relations between work-related risk factors and sick leave . Sick leave may have been the result of exposure to these risk factors , but once patients were on sick leave work-related risk factors no longer seem to have an impact on continued sick leave . Half of the patients who reported sick leave within the 3 months before baseline also reported sick leave in the 3 months following baseline . The effect of sick leave in the months preceding baseline apparently outweighed the impact of work-related risk factors in the analyses . The proportion of patients reporting sickness during the 3 months follow-up was too small to be able to exclude patients reporting sick leave at baseline . Cox regression produces large estimates of the standard errors , which results in conservative estimates of the confidence intervals -LRB- Skov et al. 1998 -RRB- . Therefore , it may be possible that relevant associations did not reach statistical significance . Sick leave data were collected by a self-reported questionnaire . Sick leave data collected by an objective method -LRB- i.e. , sick leave records -RRB- may be more accurate than self-reported sick leave . However , in large epidemiological studies the use of questionnaires is more feasible and can be a source of reliable data on sick leave . Burdorf et al. -LRB- 1996 -RRB- investigated the reliability of self-reported sick leave with company records as reference . A good agreement was found between prevalence , frequency and duration of self reported sick leave and company records in patients with back pain . In our study we only examined the prevalence of sick leave and consider the reported sick leave data to be fairly reliable . Our study population differs from an occupational cohort , consisting of workers from a wide variety of occupational settings who had visited the GP due to neck or upper extremity complaints . This makes our results more widely generalisable than a selective sample of workers from a specific company or industry . However , due to the fact that our population already had symptoms at baseline we may not be able to discriminate between factors that are a consequence of sick leave at baseline and factors that may increase the risk of sick leave . For example , patients may worry more about their pain problem because they are no longer able to work , or worrying about their pain problem may be the reason for sick leave after their visit to the doctor . In the Netherlands the GP is often confronted with patients who are on sick leave due to musculoskeletal complaints , as patients who seek medical care usually first consult their GP . The GP acts as a gatekeeper in the health care system . At the time of our study , referrals to the second or third level of care could , in principle , only be made by the GP . This is comparable to , for instance , the British and the Canadian health care systems . As a result of their position in the Dutch health care system , GPs could play an important role in the prevention of aggravation of complaints . In this study the copying style `` worrying '' seemed to be an important factor in patients who have jobs involving heavy physical work . Reassuring patients might help to reduce aggravation of complaints , which might improve the chances of return to work in this group of patients with neck or upper extremity complaints . It may be interesting to investigate whether early intervention aimed at promoting particular coping styles can prevent or reduce sick leave in patients with neck or upper extremity complaints in a primary care setting . In conclusion , heavy physical work increased the risk of sick leave and prolonged sitting reduced the risk of sick leave in a subgroup of patients who worry much . Other work-related physical risk factors and work-related psychosocial risk factors were not significantly related to sick leave . Additional large longitudinal studies of sufficiently large size among employees with neck or upper extremity complaints are needed to confirm our results .

O O O O O O O B I O O O B O B I O O O O O O O O O O O B I O O O O O O O O O B O B I O O O O O O O O B O B I O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O B O B I O O O O O O O O B O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B I O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B I O O O O B I O O O O B I O O O B O O O O O O B O O O O O O O O O O O O O O O B I O O B O O O O O O O O O O O O O O O O O O O O O O O B I O O O B O O B O O O O B I O O B O B I O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O B I O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O B O B I O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O B I O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O B O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O B I O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B I O O O O O O O O B I O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O B I O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O B I O O O O O O O B I O O O O O O O O B I O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O B I O O O O O O O O O B 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O O O O O B O B I O O O O O O O O

cohort study
sick leave
workload
neck
upper extremity


The prescribing of prisms in clinical practice The use of prisms in cases of decompensated heterophoria is an established treatment modality . The clinical literature lacks consensus upon the appropriate use of prisms , and fails to provide the necessary evidence base . While the experimental literature can guide the practitioner , the lack of double-blind , placebo-controlled clinical studies needs to be addressed . The use of prisms in cases of binocular dysfunction is an important treatment modality for dealing with such patients -LSB- 1 -RSB- . The decision to prescribe a prism , and what value of prism to give , is subject to varying clinical opinions and practices -LSB- 2 -RSB- . The conservative view in clinical practice is that prisms should not be prescribed in the absence of symptoms of binocular dysfunction -LSB- 1 -RSB- . Furthermore , the prescribing of prisms is contraindicated in certain cases , due to the risk of exacerbating an existing condition through the process of vergence adaptation -LSB- 3 -- 6 -RSB- . The control of the vergence response has been described previously using linear systems modelling -LSB- 7 -RSB- , and can aid our understanding of the aetiology of binocular visual dysfunction , and the effect of clinical intervention . The normal vergence response operates in a closed-loop feedback system , where the total response is the sum of the outputs of two control elements with differing temporal properties ; a fast -LRB- phasic -RRB- control element and a slow -LRB- tonic -RRB- adaptive control element -LSB- 7 -RSB- . Previous reports have suggested that the strength of the adaptive vergence control element is often related to the presence of symptoms in patients with binocular dysfunction , and in severe cases the output of the adaptive vergence controller may be reduced to almost zero -LSB- 8 , 9 -RSB- . In less severe cases , vergence adaptation may be present at a sub-normal level , but sufficient to produce an adaptive response to the introduction of a prism -LSB- 8 -RSB- . In such patients , strengthening the adaptive vergence control element is the treatment of first choice -LSB- 8 , 9 -RSB- . Other studies have shown that in elderly patients vergence adaptation is very limited , and that while this may often be the cause of binocular dysfunction in these patients , remedial action with prisms is clinically viable because adaptation is very unlikely -LSB- 10 -RSB- . Indeed , we observe in our own binocular vision clinic that treatments designed to improve the strength of the adaptive vergence controller are generally unsuccessful in elderly patients . Typical clinical measures of binocular function , three of which are investigated by Otto et al. -LSB- 11 -RSB- in the current issue , are : Heterophoria -LRB- or dissociated phoria -RRB- . This represents the fusion-free position of the eyes , and therefore the magnitude of the deviation which has to be overcome by the vergence system.Fixation disparity.First investigated by Ogle -LSB- 12 -RSB- , this represents a small misalignment of the visual axes during binocular viewing , normally measured in seconds of arc . Many clinicians take the view that fixation disparity is indicative of stress within the binocular system -LSB- 1 -RSB- . Other authors regard fixation disparity to be a purposeful error , necessary for the vergence control system -LSB- 5 -RSB- . Associated heterophoriaMallett -LSB- 13 , 14 -RSB- is the author associated with describing the clinical characteristics of this measurement , which measures the amount of prism required to reduce any fixation disparity -LRB- in 2 above -RRB- present to zero . In Mallett 's opinion , the presence of an associated phoria in a patient with symptoms of binocular vision dysfunction is indicative of stress within the binocular system , and requires treatment -LSB- 15 -RSB- . Fusional vergence reserves.This is a clinical measure of the overall ability of the vergence system to control heterophoria . It is generally used in the calculation of Sheard 's Criterion -LSB- 16 -RSB- , which requires the vergence reserves to be at least twice the size of any heterophoria present . There is evidence that the vergence reserves are related to the strength of the adaptive component of the vergence system -LSB- 8 , 9 -RSB- . Each of these measures assess one specific aspect of binocular function , and while some practitioners prefer to rely on a particular measure to assess binocular function , others may assess a combination of the measures above to decide the most appropriate clinical intervention for the patient -LSB- 2 -RSB- . There is a lack of consensus in the literature about which of these measures correlates most closely with symptoms of binocular dysfunction , and which provides the most accurate basis for prescribing a prism when this is appropriate . Previous work has shown that no single measure correlates well with patient symptoms in all types of binocular anomaly , suggesting that neither fixation disparity , nor associated phoria , provide a universal indicator of binocular dysfunction -LSB- 17 -RSB- . This work also found that measures of vergence reserves often showed a better correlation with symptoms -LSB- 17 -RSB- . The imperative question for the clinician remains ; is there a reliable method to determine the magnitude of prism required to compensate the heterophoria in patients suitable for this method of treatment ? Mallett -LSB- 15 -RSB- suggested that the associated heterophoria identified the uncompensated portion of the binocular anomaly , and therefore this value represented the prism required to give the patient binocular comfort and stability . Other studies have questioned this -LSB- 5 , 17 -RSB- , and indeed the presence of an associated phoria in patients without binocular visual problems casts doubt on the general applicability of this measure -LSB- 18 -RSB- . Sheard 's criterion provides a rationale for prescribing prisms -LSB- 1 , 18 -RSB- ; however , there is still a lack of randomised controlled clinical trials to prove the efficacy of any treatment of binocular vision -LSB- 2 -RSB- , although a recent study has begun to address this -LSB- 19 -RSB- . The use of a measure such as the `` comfortable prism '' , while clinically appealing , is highly subjective in nature , and would also require a clinical evidence base to prove efficacy . There is considerable work still to be done in the field of clinical management of binocular vision dysfunction in order to provide the required evidence base . In all cases of binocular dysfunction , the choice to prescribe prisms lies with the clinician , who must judge what is most appropriate for each individual patient . A relatively straightforward procedure has been described to assess the probability of vergence adaptation occurring and rendering any prescribed prism ineffective -LSB- 20 -RSB- . Where prism treatment is being considered , obtain a prior measurement of the associated phoria , insert the prism to be prescribed into the trial frame and measure the associated phoria with the prism in situ . Allow the patient to wear the prism for 10 minutes ; if the associated phoria returns to the value measured prior to insertion of the prism , then the patient 's vergence adaptation mechanism has been strong enough to overcome the prism , and it will have little clinical benefit . Conversely , if no vergence adaptation is observed , the patient is likely to derive significant clinical benefit from this treatment .

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