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AlzRisk Paper Detail

Reference: Beydoun, 2008
Cohort: Baltimore Longitudinal Study of Aging
Risk Factor: Obesity

Exposure Detail
The authors evaluated effect estimates for men and women separately for ages 30, 35, 40, 45, and 50. The data given in this row correspond to men of age 30.

Method of ascertaining BMI: technician measurement

"Height and weight were measured with calibrated scales
by trained technicians. At each study visit, BMI was calculated."

"Linear mixed models were fitted to sample 1 (n = 3,005
subjects) to estimate predicted values of BMI and waist circumference at ages 30, 35, 40, 45, and 50 years, using age at visit as the time variable (the method is described in Web Appendix 1, presented on the Journal’s website ( Predicted BMI values at each target age were categorized on the basis of World Health Organization guidelines (32) as follows: <18.5 (underweight), 18.5–24.9 (normal), 25–29.9 (overweight), and >= 30 (obese)."

"Covariates considered in predictive models for BMI and waist circumference in our main analyses included age at visit, gender, race/ethnicity (non-Hispanic white, non-Hispanic black or other), years of education, smoking status (never, former or current smoker), and year of birth."

Age Detail
"Subjects entered follow-up at age 30 years, were entered
into the risk set at age 50 years, and exited follow-up at first failure, defined as being diagnosed with incident AD at or beyond age 50 years or being censored at the end of follow-up due to death or attrition."

Screening and Diagnosis Detail
AD Diagnosis:
NINCDS ADRDA National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association Criteria (McKhann 1984)

"Subjects showing changes that indicated incident dementia
were systematically studied. Diagnoses of dementia and
dementia type were formulated during multidisciplinary
evaluations based on prospectively collected evidence using
National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association criteria. Estimation of age at AD onset was based on informant reports and history of disease-free examinations."

Covariates & Analysis Detail
Analysis Type:
Cox proportional hazards regression

"We used Cox proportional hazards to examine risk of AD associated with early to mid-adulthood adiposity status and change. The dependent measure was age at onset of AD or the last observed (censored) age of nondiagnosed subjects. All of our primary analyses were stratified by gender."

"Our Cox proportional hazards models controlled for education,race/ethnicity, smoking status, and year of birth. The exposure was the adiposity status measure (BMI or waist circumference) at a specific age or 5-year change. High-risk groups for men and women were derived empirically and compared with the rest of the population within each gender in terms of risk for AD. To this end, Kaplan-Meier survival curves and log-rank tests (35) were used to compare the number of incident AD cases across risk groups."

AD Covariates:
SMsmoking status
YOByear of birth