Figure. Association Between Categorical Change in Smoking Intensity and Risk of Dementia.

Quitters were defined as those who stopped smoking; reducers (I and II), those who decreased the number of cigarettes smoked per day by at least 20%; sustainers, those who decreased or increased the number of cigarettes smoked per day by less than 20%; and increasers, those who increased the number of cigarettes smoked per day by at least 20%. The hazard ratio was adjusted for age, sex, household income, alcohol consumption, regular physical activity, area of residence, comorbidities, and body mass index. Error bars represent 95% CIs. aHR indicates adjusted hazard ratio.