Association between weight-adjusted waist index and the incidence of low back pain among middle-aged and older adults: a nationwide prospective cohort study in China.

PURPOSE: This study aimed to investigate the prospective association between cumulative average weight-adjusted waist index (WWI), a novel indicator of central obesity, and the incidence of low back pain (LBP) among middle-aged and older Chinese adults, and to assess its consistency across subpopulations.

METHODS

Data were from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2015), including 7,123 participants aged ≥ 45 years without baseline LBP. Cumulative average WWI was calculated as waist circumference divided by the square root of body weight and categorized into quartiles. Multivariable logistic regression assessed the association with incident LBP. Restricted cubic spline analyses evaluated nonlinear relationships, and subgroup and sensitivity analyses tested robustness.

RESULTS

Over a 4-year follow-up, 1,561 participants (21.9%) developed LBP. Compared with the lowest quartile of cumulative average WWI (Q1), participants in the highest quartile (Q4) had a significantly higher risk of LBP (OR = 1.27, 95% CI: 1.05-1.54; p for trend = 0.027). Each 1-SD increase in WWI was associated with a 10.2% higher risk of LBP (OR = 1.10, 95% CI: 1.03-1.18). Restricted cubic spline analyses demonstrated a J-shaped association (p for nonlinearity = 0.016). Stronger associations were observed among women and individuals with dyslipidemia (p for interaction < 0.05). Sensitivity analyses confirmed the robustness of these findings.

CONCLUSION

Elevated WWI is nonlinearly associated with higher LBP risk, particularly in women and individuals with dyslipidemia, indicating cumulative central obesity is an independent risk factor for low back pain in middle-aged and older adults.