Covariates
Covariates were defined using data collected at baseline.
The selection of variables was based on previously identified risk factors of dementia and stepwise model building
procedures ( P o .20 for inclusion). Educational status was
categorized as 3 or less versus 4 or more years of formal
education because, at the time the CSBA participants went
to school, the first educational degree was achieved after 3
years of schooling. Participants were defined as sedentary if
they did not adhere to current recommendation for physical
activity (30 minutes or more of moderate intensity physical
activity on at least 5 days per week).20 Trained interviewers
collected information on physical activity at baseline using
the Paffenbarger Physical Activity Questionnaire.