ObjectivesImproved health may extend or shorten the duration of cognitive impairment by postponing incidence or death. We assessed the duration of cognitive impairment by BMI, smoking and levels of education.MethodsMultistate life tables estimated the duration of cognitive impairment. Regression models determine the age specific transition probabilities to disease and death in a both genders and threeraces of the US population from the Health and Retirement Survey (HRS), 1992-2004. Exposures are self-reported BMI, smoking and education, outcome is cognitive functioning determined bythe Telephone Interview Cognitive Screen (TICS).ResultsAt age 55, white men and women may expect to live respectively 1.7 (1.5; 1.9) and 2.7 (2.4; 2.9) years with cognitive impairment. Black non-Hispanic males and females live 3.7 [2.8,4.6] and 3.7[3.0,4.5] years longer with cognitive impairment than whites. BMI makes no difference. (Ever) smoking decreases duration of cognitive impairment among men and women with respectively 0.7 [0.3,1.2] and 0.9 [0.5,1.3] years compared to never smokers. Highly educated men andwomen expect to live respectively 1.1 [0.7,1.4] and 1.9 [1.4,2.4] years with cognitive impairment, lowly educated men and women 2.7 [2.2,3.1] and 3.8 [3.3,4.3] years with cognitive impairment.DiscussionOur findings confirm the brain reserve hypothesis. While life extension increases the duration of dementia, higher levels of education compress this cognitive disability. Large differences by race remain after controlling for risk factors.