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

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

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.

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.

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.

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.