Study population and survey.
The study was conducted in a region of southern Sweden with 170,000 inhabitants with demographic characteristics similar to the Swedish general population (6). From this region's general population register, 3,000 people (age 25–74 years) were randomly selected by computer in an age- and sex-stratified sample.
A questionnaire was used for data collection. The questionnaire contained scales concerning general health, bodily pain, and physical function (7), as well as questions about activities involving the upper extremities and about the presence, location, duration, frequency, and severity of the symptoms of pain (3), numbness, and tingling in any part of the body (see Appendix A). It also contained questions regarding morbidity, sociodemographic data, smoking habits, and physical exercise (3).
Location of symptoms was determined by specific questions covering the different parts of the body. The question regarding duration of the symptoms had 5 response options (ranging from “1 month” to “more than 1 year”) to be indicated for each body location. Symptom severity was reported on a 5-point scale ranging from 1 (mild), to 5 (most severe) for each body location. The question regarding frequency of the symptoms had 5 response options ranging from “almost every day” to “once a month.” The questions concerning physical impairment inquired about the degree of limitation in ability to perform a number of specific daily activities. Each of the questions had the response options “not limited at all,” “limited a little,” and “limited a lot.” The sociodemographic factors studied were age, sex, weight, height, socioeconomic level, work status, smoking habits, and frequency of performing physical exercise.
The ethics committee of the medical faculty of Lund University approved the study.
Following information in the local media, the questionnaire (together with information about the general health survey and a prepaid return envelope) was distributed to the persons by mail in January 1997. Two reminders were sent after 3 and 6 weeks to those who did not respond.
For the analysis, chronic pain and chronic numbness or tingling were defined as current self reported symptoms of at least 6-months duration, with a severity rating of at least 2 on a scale from 1 (mild) to 5 (most severe) and a frequency rating of having been experienced at least weekly. This definition was used for all prevalence calculations, including those for pain in the neck, low back, and lower extremities. Physical function was assessed by inquiring about ability to perform specific daily activities. Physical impairment was defined as a response of “limited a lot” for at least 1 activity involving the upper extremities.
Body mass index (BMI) was categorized according to the World Health Organization's cut points (BMI ≥ 25.0 classified as overweight). For the analysis, socioeconomic level was grouped according to the method used by Statistics Sweden into blue-collar workers, white-collar employees, and others. Long-term work absence was defined as sick leave of more than 3-months' duration, disability pension, or early retirement. Smoking was categorized as “current or former smoker” or “nonsmoker.” Physical exercise was categorized as regular (at least weekly) and not regular (less often than weekly).
The accuracy of the responses to the questionnaire was assessed by interview and clinical evaluation of 421 of the responders (287 symptomatic and 134 asymptomatic) 2 months after the mail survey (8).