Association of body mass index with chronic pain prevalence: a large population-based cross-sectional study in Japan.

PURPOSE: The aim of this study was to examine the association between body mass index and chronic pain.

METHODS: The outcome was chronic pain prevalence by body mass index (BMI). BMIs of less than 18.5, 18.5-25.0, 25.0-30.0, and 30.0 or over kg/m2 were defined as underweight, normal weight, overweight, and obese.

SUBJECTS: We used data from 4993 participants (2464 men and 2529 women aged 20-79 years) of the Pain Associated Cross-sectional Epidemiological survey in Japan. Sex-stratified multivariable-adjusted odds ratios were calculated with 95% confidence intervals using a logistic regression model including age, smoking, exercise, sleep time, monthly household expenditure, and presence of severe depression. We analyzed all ages and age subgroups, 20-49 and 50-79 years.

RESULTS: The prevalence of chronic pain was higher among underweight, overweight, and obese male respondents than those reporting normal weight, with multivariable odds ratios of 1.52 (1.03-2.25), 1.55 (1.26-1.91), and 1.71 (1.12-2.60). According to underweight, only older men showed higher prevalence of chronic pain than normal weight men with odd ratios, 2.19 (1.14-4.20). Being overweight and obese were also associated with chronic pain in women; multivariable odds ratios were 1.48 (1.14-1.93) and 2.09 (1.20-3.64). Being underweight was not associated with chronic pain.

CONCLUSION: There was a U-shaped association between BMI and chronic pain prevalence among men ≥ 50 years, and a dose-response association among women. Our finding suggests that underweight should be considered in older men suffering chronic pain.