EXPLORING THE ASSOCIATION BETWEEN SMOKING AND DEMENTIA AMONG A MIDDLE TO OLD AGE POPULATION IN THE UNITED STATES

Background: Smoking is a well-known risk factor for both cardiovascular disease (CVD) and dementia. However, to date, few studies have examined whether CVD mediates the relationship between smoking and dementia or whether this relationship is modified by gender or race. Methods: This study analyzed data from the 15th wave (2020–2021) of the Health and Retirement Study (HRS), including U.S. adults aged 50 and above. Participants’ self-reported information on smoking and heart disease was used. Dementia diagnosis was based on self- or proxy-report. Logistic regression models were used to estimate the total effect of smoking on dementia (without CVD adjustment), the direct effect of smoking on dementia (adjusting for CVD), and the association between smoking and CVD, controlling for covariates. Mediation analysis assessed whether CVD mediated the relationship, estimating indirect, direct, and total effects. Interaction and stratified analyses evaluated gender and race as potential effect modifiers, adjusting for CVD and covariates. Results: Smoking was significantly associated with dementia risk, showing a total effect (95% CI: 2.76e-6, 0.00031; p < 0.05), a direct effect (95% CI: 4.28e-7, 0.000276; p < 0.05), and an indirect effect mediated through CVD (95% CI: 1.17e-6, 0.000290; p < 0.05). Stratified analysis showed a significant association between smoking and dementia among females (OR = 1.31; 95% CI: 1.06, 1.63) and White populations (OR = 1.35; 95% CI: 1.08, 1.69), whereas no statistically significant associations were observed among males (OR = 1.24; 95% CI: 0.82, 1.89), Blacks (OR = 1.04; 95% CI: 0.64, 1.69), Hispanics (OR = 1.46; 95% CI: 0.87, 2.46), or other races (OR = 1.15; 95% CI: 0.53, 2.53). Interaction analyses indicated that neither gender (p: 0.76) nor race (p: 0.68) were modifiers of the smoking-dementia relationship. Conclusions: Smoking was associated with dementia both directly and indirectly through CVD. Stratified analyses showed significant associations between smoking and dementia only among females and White populations. However, the interaction analyses indicated that gender and race were not modifiers of the relationship. Further research with larger and more balanced samples is needed to assess potential effect modification by gender and race.