Longitudinal associations of body mass index and abdominal circumference with back pain among community-dwelling adults: data from the Osteoarthritis Initiative

BACKGROUND CONTEXT: Back pain is the most common musculoskeletal problem in both developed and developing countries. The prevalence and burden of back pain increases with age, and the management of back pain becomes increasingly important in the context of global aging. There is increasing evidence that obesity is a modifiable risk factor for musculoskeletal pain in different locations. Understanding the role of obesity in back pain holds great potential for improving understanding of the mechanisms of back pain and for developing new preventive and therapeutic approaches. PURPOSE: To evaluate the role of weight, body mass index (BMI) and abdominal circumference (AC) in risk of back pain over 96 months. DESIGN: Prospective cohort study. PATIENT SAMPLE: The sample was from 4,793 adults in the Osteoarthritis Initiative (OAI) database who had or were at increased risk for knee Osteoarthritis. OUTCOME MEASURES: Outcome variables included the presence, severity, and frequency of back pain, using the past 30 days as the time frame. METHODS: Longitudinal analysis of data from 4,793 participants enrolled in the Osteoarthritis Initiative, assessed every 12 or 24 months for weight, BMI (kg/m(2)), AC (cm), and presence, severity (none, mild, moderate, severe), and frequency (none, rarely, sometimes, often, always) of back pain. BMI and AC were decomposed into between-person and with-person components. Data anal-yses were performed using mixed-effects logistic (for presence of back pain) or ordered logistic regression (for severity and frequency of back pain) models. RESULTS: Back pain was reported in 58% of participants at baseline; 70% of those without back pain had incident back pain over 96 months. Both between-person (average value across a participant's all measurements) and within-person (deviations from the participant's average) effects of weight and BMI increased risk of presence, severity, and frequency of back pain (Odds radios (OR) per kg/m(2): 1.010-1.046, p<.05) in females but not males, with statistically significant weight*sex and BMI*sex interactions. Similar findings were observed for between-person effects of AC on back pain, and the within-person effect of AC was only associated with back pain severity (OR per cm: 1.009, 95% confidence interval 1.002-1.017, p=.019) in females. CONCLUSIONS: Greater average weight and BMI and increases in them increased odds of presence, severity, and frequency of back pain over 96 months in middle aged and older women but not men. Only average AC increased odds of back pain over time, in women. These findings suggest that preventing obesity and slowing weight gain is important for the management of back pain.