Back Pain Severe Risk for Morbidly Obese; Mild Exercise May Help

At the North American Spine Society (NASS), this year held on the banks of the Mississippi in the Big Easy, a new study that found a new correlation between obesity and back pain was presented. The study, titled “Does Physical Activity Influence the Relationship Between Low Back Pain and Obesity?” found that being morbidly obese increases the risk of back pain four fold.

“Historically, based on anecdotal evidence and very limited studies, spine specialists have told overweight patients that losing a relatively modest amount of weight or even marginally increasing their exercise can help reduce their risk of back pain,” said Michael L. Reed, PT, DPT, OCS, MTC, a spine specialist with the Hospital for Special Surgery and NASS annual meeting program co-chair. “This large, precise study finally provides the hard data we need to back up those beliefs and really help to put weight behind our words as we make these recommendations to our patients.”

The study, which won a 2013 “Outstanding Paper” award from The Spine Journal, noted that despite the quadrupled risk for back pain in morbidly obese patients, just 20 minutes of light exercise each day can lower that risk by 32 percent.

The researchers performed a cross-sectional U.S. population-based study of a cohort of 6,796 adults from the 2003-2004 National Health and Nutrition Examination Survey (NHANES). Lower back pain (LBP) status was determined by questionnaire response. Body mass index was calculated during physical examination and divided here into four groups (normal weight 25, overweight 25-30, obese 31-35, and morbidly obese over 36). Summary measures of physical activity were computed based on intensity cut-offs, percentile intensities, and bout. Demographics, social history, and comorbid health conditions were used to build adjusted-weighted logistic regression models.

The researchers concluded that in the U.S. population, the risk of low LBP increases in step with BMI from 2.9 percent for normal BMI, to 5.2 percent for overweight, 7.7 percent for obese, and 11.6 percent for morbidly obese. Smoking is consistently the strongest predictor of LBP across the BMI spectrum, but as mentioned above, physical activity modulates these risks. In the overall model, the best physical activity predictors of LBP are in the moderate and high intensity ranges with small effects. When broken down by BMI, time spent in sedentary and moderate activity ranges demonstrates more robust influences on LBP status in the overweight, obese and ultra-obese groups.

“Perhaps the best news out of this study is that big gains can be made by making some incredibly modest changes in activity,” said lead author Matthew Smuck, M.D., chief of physical medicine and rehabilitation and associate professor at the Stanford University School of Medicine.

The study found:

• When the average, overweight person stops being sedentary and starts moving (including even very light activity such as folding clothes or walking slowly) he or she will remain active, on average, for 1 hour and 53 minutes. Simply extending this average by seven minutes—to two hours—reduces the risk of back pain by 17 percent;
• For overweight Americans, increasing the amount of time in moderate activity (examples include: brisk walk, water aerobics, riding a bike, ballroom dancing, and general gardening) by less than 20 minutes/day can reduce back pain risk by 32 percent; and
• Simply pushing just a little harder during a bout of exercise is very beneficial. For people who are morbidly obese, the average duration of time spent doing a moderately-intensive activity (examples include brisk walking, water aerobics, bike riding, ballroom dancing and general gardening) was found to be 1.3 minutes. Extending this average time at or above the moderate activity intensity range by less than one additional minute every time they exercise reduces their odds of having back pain by 38 percent.