Weight changes after smoking cessation and the risk of hip fractures: a nationwide population-based cohort study

Smoking cessation reduces hip fracture risk; however, subsequent weight loss may offset this benefit. In a nationwide cohort, weight loss after smoking cessation was associated with increased hip fracture risk. Maintaining stable body weight after quitting smoking may be important for fracture prevention.

Smoking cessation reduces fracture risk but is often accompanied by changes in body weight that may influence bone health. However, it remains unclear whether weight change after smoking cessation is associated with hip fracture risk. We therefore examined the association between post-cessation weight change and the incidence of hip fractures.

This retrospective cohort study used data from the Korean National Health Insurance Service. Adults aged ≥ 40 years who underwent consecutive biennial health examinations in 2007 and 2009 were categorized as nonsmokers, quitters, or current smokers based on their smoking status. Quitters were further stratified by weight change between two examinations: loss (> 5% decrease), weight maintenance (± 5%), or weight gain (> 5% increase). Participants were followed from 2010 through 2018 for incident hip fractures. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using multivariable Cox proportional hazards models.

Among 913,805 participants (672,858 nonsmokers; 34,143 quitters; 206,804 current smokers), 6,001 incident hip fractures occurred during a mean follow-up of 8.1 years. Compared with nonsmokers, current smokers had a higher risk of hip fracture (aHR = 1.700, 95% CI 1.557-1.856). Quitters also showed increased risks across all weight-change categories: weight loss (aHR = 1.878, 95% CI 1.164-3.031), weight maintenance (aHR = 1.461, 95% CI 1.188-1.797), and weight gain (aHR = 1.611, 95% CI 1.151-2.255). Quitters who maintained or gained weight had numerically lower risk estimates than current smokers, whereas those who lost weight had a higher point estimate; however, confidence intervals overlapped across groups. In analyses of the entire cohort, both weight loss (aHR = 1.425, 95% CI 1.336-1.519) and weight gain (aHR = 1.150, 95% CI 1.064-1.242) were associated with higher hip fracture risk compared with weight maintenance.

Smoking cessation was associated with a lower risk of hip fracture than continued smoking, although the risk remained higher than in nonsmokers. Weight loss after smoking cessation was associated with higher fracture risk, while maintaining stable body weight appeared to be associated with more favorable outcomes. These findings suggest that maintaining a stable body weight after smoking cessation may be important for hip fracture prevention.