Relationship between obesity, sleep duration and rheumatoid arthritis in middle-aged and elderly of China: Evidence from a nationally representative cross-sectional study

Obesity and insufficient sleep have been linked to increased rheumatoid arthritis risk, but evidence on their combined effects remains limited. This study examined the joint association of body mass index (BMI), nap duration, and nighttime sleep duration with rheumatoid arthritis prevalence among middle-aged and older Chinese adults. Data from 10,127 individuals aged 45 years and older, obtained from the 2015 China Health and Retirement Longitudinal Survey (CHARLS), were included in this analysis. Multivariate logistic regression was performed. The risk of arthritis was the highest in the group with BMI values ≥ 28 kg/m2/nap duration of 1–30 min (odds ratio (OR) = 2.199, P = 0.007) compared with those with 18.5 kg/m2 ≤ BMI ≤ 23.9 kg/m2/0 ≤ nap duration ≤ 30 min. The risk of arthritis was the highest in the group with BMI kg/m2≥ 28/0–6 h of nighttime sleep duration (OR = 1.478, P = 0.003) compared with those with normal BMI/6–8 h of nighttime sleep duration. Coexisting obesity and insufficient nighttime sleep or absence of daytime nap significantly increase the risk of rheumatoid arthritis. Based on these findings, individuals may benefit from maintaining a healthy body weight through balanced diet and regular physical activity, and ensuring adequate nighttime sleep, as part of strategies to potentially reduce rheumatoid arthritis risk in middle-aged and older adults.