Friday, October 21, 2011

Influences of Exercise on Chronic Pain Examined

Exercize Pain Chronic pain may be associated with too much or too little physical activity. New research finds that the right amount, duration, and intensity of leisure-time exercise can make a significant difference in who has long-lasting pain, but there also are differences between men and women and younger versus older age groups.

In the October issue of the journal PAIN, Tormod Landmark and colleagues from Norway report an analyses of a large-scale, prospective survey on daily physical activity and chronic pain. This was part of a large Norwegian study among adults — the Nord–Tr√łndelag Health Study (HUNT) — the third wave of which (2006–2008) included a simple measurement of pain as well as data on leisure-time physical activity that distinguished between frequency, duration, and intensity of the exercise.

Of 94,194 persons invited to participate, complete data were obtained from 46,533, and separate analyses were performed for the working-age population (20–64 years) and the older population (aged 65 years or more). When defined as pain lasting longer than 6 months, and of at least moderate intensity during the past month, the overall prevalence of chronic pain was 29%, but this was more common in women (33%) than men (26%) and increased with age.

The researchers found that increased frequency, duration, and intensity of exercise were associated with less chronic pain in analyses adjusted for age, education, smoking, and organ-specific disease. In persons aged 20 to 64 years, the prevalence of chronic pain was 10% to 12% lower for those exercising 1 to 3 times a week for at least 30 minutes duration with moderate intensity, relative to those not exercising. The prevalence of chronic pain was 21% to 38% lower among older women who exercised, relative to those not exercising, and a similar, but somewhat weaker, association was seen for older men.

The researchers conclude that this study shows consistent and linear associations between increased frequency, duration, and intensity of exercise and less prevalence of chronic pain for the older population, and associations without an apparent linear shape for the younger, working-age population. In younger persons, too little or too much exercise resulted in a greater prevalences of chronic pain, compared with a more moderate approach.

COMMENTARY: This study is a good example of the axiom that the closer one looks at medical research on humans the more complicated it becomes. The authors set out with a simple question: Is exercise activity associated with a lower prevalence of chronic pain? But a more complete answer required them to examine the frequency, duration, and intensity of exercise, in men versus women, and in different age groups, while controlling for other factors, such as health status (smoking, disease), education level, and the presence of depression/anxiety.

The overall prevalence of adult chronic pain (29%) in this Norwegian population is somewhat consistent with the latest proportional data in the United States (116-million adults). Interestingly, the prevalence was 10% lower in those who never smoked compared with current or former smokers. Unsurprisingly, there was an almost 2-fold increase in chronic pain prevalence among subjects with depression/anxiety and in those with more than one organ-specific disease (eg, cardiovascular disease, lung disease, diabetes, cancer, epilepsy).

The research questionnaire focused largely on common types of everyday recreational activities — such as walking, skiing, swimming, bicycling, or other sports — rather than supervised physical training or exercise. Differences between and relative advantages of the various specific types of activity were not explored in the research.

Participants were asked to record how often they engaged in activities and for how long each time, as well as the average intensity (eg, from easy to near exhaustion). Certainly, there was a potential for recall bias (eg, “I usually walk a few times a week, rather rapidly… I think.”) and a social desirability bias (eg, “Of course I exercise regularly, doesn’t everybody?”). Expectedly, the very large sample size overcame these deficiencies in response accuracy among some participants.

Overall, the prevalence of non-exercise increased with age, smoking status, and with having one or more organ-specific diseases, as well as with depression/anxiety. Non-exercise was surprisingly higher among men (29%) than women (20%), but the prevalence of non-exercise decreased with higher levels of education.

In general, older persons (≥65 years of age) exhibited less chronic pain as the frequency, duration, and intensity of their recreational exercise activities increased, but this was more pronounced in women than men in this age group. It might be expected that the levels of these variables would be moderated by age — that is, elderly persons would engage in less strenuous activities or sports than their younger counterparts — but this was not fully explored in the research.

Of interest, in the younger population (20-64 years) the prevalence of pain was similar for those not exercising and in those exercising almost every day; whereas, it was lowest in those exercising 1 to 3 times a week. This seems to support the old adage, “Too much or too little of a good thing can be bad — moderation is best.”

Finally, it also should be understood that a cross-sectional survey such as this — capturing a snapshot of a population segment during a given timeframe — and using subjective and self-reported measures does not determine a direct cause-effect relationship between exercise and chronic pain. While researchers may be interested in the subtle nuances of this study, the message for clinical healthcare providers and their patients appears to be: regular leisure-time exercise activities might be helpful in reducing the likelihood of chronic pain at any age; however, moderation is best and adjustments may be necessary to account for current health status.

One guideline for cardiorespiratory and muscular fitness, from the American College of Sports Medicine, recommends that, to the extent possible, adults should be moderately active for at least 30 minutes on most days of the week, preferably all days, and be vigorously active for a minimum of 20 minutes on at least 3 days each week.

REFERENCE: Landmark T, Romundstad P, Borchgrevink PC, et al. Associations between recreational exercise and chronic pain in the general population: Evidence from the HUNT 3 study. Pain. 2011(Oct);152(10):2241-2247 [abstract here].