Widespread Musculoskeletal Pain and the Progression of Disability in Older Disabled Women

Musculoskeletal pain is a common cause of disability in older adults (1-4). Recent attempts to understand the impact of pain on daily function in older persons have demonstrated the complexity of the problem in the elderly (2, 3). Often, musculoskeletal pain affects more than one or two joint areas, and the cause is unknown. In fact, although musculoskeletal pain is often attributed to arthritis, joint pain is associated with an increased risk for functional difficulties, even in the absence of radiographic evidence of arthritis (5). In epidemiologic studies, many aspects of pain have been associated with disability, including frequency, intensity, and location (2, 3). The lack of specificity of musculoskeletal symptoms reported in the older population belies the serious effects of this chronic problem on quality of life and health care costs. How often do clinicians hear their older patients and, most often, women, say I hurt all over? Population-based surveys have found that the prevalence of widespread pain is highest in persons 60 to 80 years of age (6, 7). These studies raise important questions about the causes and the scope and effect of widespread-pain syndromes in the older population. The role of widespread pain as a disabling condition in the older population is poorly understood. Investigators have reported that most persons with pain at several sites have at least some disability (4). We examined whether widespread pain increased the risk for worsening disability in older women with disability living in the community. Methods Study Design The Women's Health and Aging Study, which began in 1992, is a population-based longitudinal study of the one third of women 65 years of age or older living at home with at least mild disability in the eastern region of the city and county of Baltimore, Maryland. Of 32 538 women identified by searching Medicare enrollment files, 6521 were sampled by using an age-stratified random-sampling approach. Of this sampled group, 5316 women were alive and living at home, and 4137 participated in the home-based screening. Eligible women were those who reported having any difficulty in at least two of four domains of functioning: upper extremity (raising arms over head, lifting or carrying 10 lbs, using fingers to grasp or handle), lower extremity (walking two to three blocks, climbing stairs, transferring from a bed or chair, doing heavy housework), higher functioning (using the telephone, performing light housework, shopping, preparing meals), and self-care activities (bathing, dressing, eating, using the toilet). Women were excluded if they had severe cognitive impairment according to the Mini-Mental State Examination (score < 18) (8). Of the 1409 eligible women, 1002 agreed to participate and provided written, informed consent. Study procedures were approved by the Institutional Review Board of the Johns Hopkins Medical Institutions, Baltimore, Maryland. Baseline assessment included a comprehensive interview and a physical examination by a trained nurse. Further details of the study methods are described elsewhere (9, 10). Data Collection All physical examinations were performed in the home; follow-up evaluations were conducted every 6 months for 3 years. If participants were incapacitated or resided in a nursing home at the time of a follow-up visit, a proxy respondent, such as a family member or caregiver, was interviewed. The response rate for each of the six follow-up interviews, including proxy responses, was approximately 93%. Proxy response rates ranged from 3% in the first follow-up interview to 16% in the final follow-up interview. Pain Measurement At the baseline interview, participants were asked two questions each about hand or wrist pain, foot pain, and back pain. Women who reported having pain on most days for at least 1 month in the past year were asked to rate the severity of their pain according to a numeric rating scale. The scale was shown on a card with numbers from 0 to 10 on a line, with 0 indicating no pain and 10 indicating severe or excruciating pain. Women who reported having hip or knee pain on most days for at least 1 month in the past year and in the past month were asked five additional questions from the Western Ontario McMaster Osteoarthritis Index (WOMAC). These participants rated their pain by using the numeric rating scale for each of the following activities: walking on a flat surface, going up and down stairs, lying in bed at night, sitting or lying down, and standing upright (11). The pain ratings for the five activities were averaged to create a summary pain severity measure for the hip or knee. Nonanginal chest pain was determined from participant reports of having chest pain in the past 2 weeks. Chest pain in women who had possible or definite angina on the basis of antianginal medication use, physician report of angina, or positive findings on the Rose questionnaire (assessing exertional chest pain) was not included. The detailed algorithm used in determining the presence of anginal chest pain has been shown previously (12). Severity of chest pain was not assessed; for this study, we considered all chest pain as at least mild pain (rating >0). Pain Categorization We categorized musculoskeletal pain into four groups according to location and severity. In 1990, the American College of Rheumatology had defined widespread pain as pain above and below the waist, pain on the right and left sides of the body, or axial skeletal pain (13). For our first category of pain, widespread pain, we used modified American College of Rheumatology criteria classifying widespread pain as pain in three regions (upper and lower extremity and axial region) with at least moderate pain (rating > 3) in one or more regions. We could not include the American College of Rheumatology criteria for contralateral pain because the Women's Health and Aging Study data did not include this characteristic. To exclude participants with only mild pain from the widespread pain category, we used information on pain severity (in addition to pain location) in our definition of widespread pain that was not part of the original American College of Rheumatology criteria. The second pain category comprised women with mild pain (rating of 1, 2, or 3) in three regions and women who did not meet the criteria for widespread pain but who reported having at least moderate pain (rating > 3) in at least one site. The third pain category comprised women with mild pain in two sites, and the final pain category was for women who reported having no pain or mild pain at only one site. Disability Measurement We studied three measures of self-reported disability: activities of daily living (ADLs), upper-extremity function, and lower-extremity mobility. Disability in ADLs was measured according to the participants' self-reported difficulty in performing each of five activities: bathing, dressing, eating, transferring from a bed or chair, and using the toilet (14). A summary ADL measure for each participant was created on the basis of the greatest level of difficulty reported in any one ADL; for example, if a woman reported an inability to bathe, then she would be considered unable in ADLs. Upper-extremity disability was assessed by self-reported difficulty lifting or carrying a 10-lb item, such as a bag of groceries (15). Lower-extremity disability was determined on the basis of participants' reported difficulty in walking one-quarter mile or two to three blocks [16]. The levels of difficulty for each measure were 1) no difficulty, 2) little or some difficulty, 3) a lot of difficulty, or 4) inability to do the activity. Measures of Health and Chronic Disease We examined sociodemographic, health, and behavioral characteristics as potential confounders of the paindisability relationship. Body mass index (BMI) was calculated in kg/m2by using weight and height measurements taken at baseline. Physical activity was categorized by using a three-level variable that was based on a summary score of the participants' self-reported amount of walking, stair climbing, heavy housework, regular exercise, dancing, bowling, and outdoor chores (17). Moderate or severe depression was based on a score of 14 or higher on the Geriatric Depression Scale (18). Self-rated health was measured by asking participants to rate their health as excellent, very good, good, fair, or poor. Major chronic conditions at baseline were ascertained by using complex algorithms that incorporated information from in-home interviews, physical examinations, medication inventories, radiographs, hand photos to determine bony prominence or deformity, hospital records, physician questionnaires, and blood tests (12). Comorbidity was measured as the number of prevalent conditions ascertained by using the disease algorithms [for angina, myocardial infarction, congestive heart failure, hip fracture, osteoporosis, rheumatoid arthritis, degenerative disc disease, spinal stenosis, stroke, Parkinson disease, pulmonary disease, peripheral arterial disease, cancer, and diabetes mellitus]. Osteoarthritis was not included in the count of comorbid conditions; because presence of pain was part of the definition of osteoarthritis in the disease algorithm, this condition could not be included as a potential confounder in the analyses. However, we did examine prevalence of osteoarthritis according to pain category. Symptomatic hip, knee, and hand osteoarthritis were assessed 1) by using the American College of Rheumatology criteria for osteoarthritis [19] and 2) according to inter-rater agreement among three epidemiologistclinicians based on the algorithm for symptomatic hip, knee, and hand osteoarthritis (range for inter-rater agreement, = 0.93 to 1.0) (12). Current use (in the previous 2 weeks) of analgesic medications (including nonsteroidal anti-inflammatory agents, opioid analgesics, and all other analgesics) was ascertained from the medication review da