Smoking cessation, weight change, and incidence and progression of frailty: A longitudinal analysis of the US Health and Retirement Study

INTRODUCTION: Smoking cessation is important for healthy ageing, but accompanying weight change may influence subsequent functional vulnerability. We examined whether attained cessation duration and weight change across the observed cessation interval distinguished later frailty risk and frailty-index progression. METHODS: This longitudinal secondary analysis included 27020 Health and Retirement Study participants with self-reported smoking and body-weight data, and valid consecutive frailty assessments who were non-frail at risk-set entry during 1998-2020. Smoking status, body weight, and covariates were assessed biennially by structured interviews. Time-varying Cox models estimated incident frailty (frailty index ≥0.25), mixed-effects models assessed annual frailty-index change, and restricted cubic splines evaluated continuous associations. RESULTS: Over a median follow-up of 8.1 years, 10641 incident frailty cases occurred during 250439.9 person-years. Compared with current smokers, quitters before baseline had lower frailty risk (hazard ratio, HR=0.79; 95% CI: 0.75-0.84), whereas follow-up quitters overall did not (HR=0.98; 95% CI: 0.90-1.07). In the duration spline, HRs at 0, 7, and 10 years of attained cessation duration were 1.14 (95% CI: 1.01-1.28), 0.79 (95% CI: 0.67-0.93), and 0.73 (95% CI: 0.60-0.89), respectively. Among follow-up quitters, >10.0 kg versus 0.1-5.0 kg weight gain was associated with higher risk (HR=1.94; 95% CI: 1.44-2.61); standardized 2-year risks among eligible analytic intervals were 15.9% and 9.5%, respectively. The direct progression contrast was imprecise in Model 3 and was estimated at β=0.415 (95% CI: 0.040-0.790; p=0.030) after additional adjustment for interval-start frailty index. CONCLUSIONS: Longer cessation duration was associated with lower frailty risk. Substantial weight gain across the observed cessation interval was associated with higher absolute frailty risk among follow-up quitters. Smoking cessation remains the priority, but marked gain may help identify quitters who warrant continued weight and functional monitoring.