Introduction:
Smoking has been associated with disease risk; however, whether smoking is an independent predictor of long-term care (LTC) certification remains uninvestigated. Therefore, this study aimed to examine the association between smoking status and LTC certification.

Methods:
This prospective cohort study was conducted using data from the Yamagata cohort study in Japan. Participants were followed for a mean of 7.6 years (SD=1.8). Individuals with available baseline data on smoking status and relevant covariates were included. The main exposure was baseline smoking status (current, former, and never smokers), and the primary outcome was LTC certification incidence during follow-up. Associations between smoking status and LTC certification were evaluated using Cox proportional hazards models, with sequential adjustment for potential confounders, including demographic factors, lifestyle habits, and comorbidities.

Results:
At baseline, the overall smoking prevalence rate was 12.4% (22.4% in men, 4.6% in women). At a mean follow-up of 7.6 years (SD=1.8), LTC certification was issued to 262 (2.6%) individuals: 137 men (3.0%), and 125 women (2.1%). Unadjusted analysis using a Cox proportional hazards model indicated a higher hazard ratio (HR) for current smokers (HR=1.44; 95% CI: 1.03–2.02), which remained significant after adjustment for sex and age (AHR=1.81; 95% CI: 1.23– 2.66). This persisted even after adjusting for sex, age, physical activity, alcohol consumption, hypertension, diabetes, and dyslipidemia (AHR=1.83; 95% CI: 1.25–2.69), and after accounting for nine factors, including stroke and ischemic heart disease (AHR=1.86; 95% CI: 1.27–2.73). Never and former smokers showed no differences in adjusted models. A sensitivity analysis excluding patients with a history of cardiovascular disease yielded similar AHRs.

Conclusions:
Overall, current smokers had a higher risk of LTC certification than never smokers, suggesting that smoking may be an independent risk factor.