BMC Public Health 2007, 7:45 http://www.biomedcentral.com/1471-2458/7/45 Table 2: Sex- and age-standardized prevalence (percentage) of self-reported reduced working capacity due to longstanding illness by the explanatory variables among people with paid employment. Explanatory variables Categories and levels Self-reported reduced working capacity due to longstanding illness (%) Total 15.0 Sickness absence (days) 0–28 10.5 29–90 29.8 >90 68.8 Sex (only age-adjusted) Male 13.2 Female 16.6 De facto marital status Living alone 16.8 Married/cohabiting 14.3 Occupational status Unskilled manual workers 20.3 Skilled manual workers 18.5 Lower level employees 15.3 Middle level employees and professionals 10.5 Employment Part-time 26.2 Full-time 12.9 Housing tenure Renting 17.2 Owning 14.2 Quality of physical working Environment Poor 22.3 Good 12.5 Presence of stress at work Yes 16.6 No 13.8 Work-related social Support Poor 19.6 Good 14.5 Discussion The main finding of this study is the strong positive gradi- ent between increasing duration of SA and increasing odds of self-reported reduced working capacity due to a longstanding illness of more than 3 months. This associa- tion remained almost unchanged after adjustment for indicators of SES, level of employment, and working envi- ronment. We found that fully 10.5% (Table 2) of the persons who had taken 0–28 SA days (this group encompasses a wide range of SA duration and is dominated by persons who took no SA) reported reduced working capacity due to a longstanding illness of more than 3 months. Further- more, when we excluded those 10.5% who reported reduced working capacity due to a longstanding illness of more than 3 months, the persons who took 0–28 SA days had a prevalence of 27.0% (Table 4) of any additional outcome. The relation between the severity of an illness and the ina- bility to work has not yet been proven [8]. It is well known that employees may be ill but not take sick leave. Further- more, most ill persons work [8]. Persons with so-called "hard" illnesses, e.g. cardiovascular diseases, normally go back to work after stroke, cardiac infarction, or heart sur- gery [8]. An interesting, unexpected, and new finding is that just under half of those on SA ≥ 29 days reported no reduced working capacity due to a longstanding illness. However, many persons in this group reported one or more of the additional outcomes (psychosomatic complaints, anxiety, or poor self-reported health). Prevalence of any additional self-reported outcome varied by number of SA days taken per year and was highest for persons absent >90 days. The range of specific health indicators in this study is limited; the main question asked was quite general, so it is possi- ble that some health problems that led to ≥29 days SA may have been missed in the study. When the result regarding the number of people who took SA but did not report longstanding illness or reduced work capacity (n = 1180) is used to estimate the corre- sponding number of people in the entire Swedish work- ing population on sick leave without longstanding illness or reduced working capacity, the figure is 174,000 per- sons. Depending on length of SA, about 38.8% to 52.9% of these people might be expected to have other health problems. If the figures from the current study sample are used to estimate the corresponding figures in the national popu- lation, the total number of people on sick leave of ≥29 days in Sweden with neither longstanding illness resulting Page 6 of 11 (page number not for citation purposes)