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Non-Steroidal Anti-Inflammatory Drugs
Washington Heights-Inwood Columbia Aging Project
Intakes of dietary and supplemental vitamin C were evaluated using a 61-item semi-quantitative food frequency questionnaire (FFQ) between the baseline and follow-up visits. The questionnaire addressed vitamin C intake during the past year. Dietary intakes were adjusted for total caloric intake using the regression residual method (Willett W, Stampfer MJ. Total energy intake: implications for epidemiologic analyses. Am J Epidemiol 1986; 124:17-27), while supplemental nutrient intakes were not calorie-adjusted. The investigators defined total vitamin C intake as the sum of the calorie-adjusted dietary intake and the non-calorie-adjusted supplemental intake. Total vitamin C intake is the focus of this entry.
"Dietary data were obtained using a 61-item version of the semiquantitative food frequency questionnaire developed by Willett et al (13) (Channing Laboratory, Cambridge, Mass). This questionnaire was administered by telephone between the baseline and first follow-up examinations by trained interviewers in English or Spanish. Intakes of carotenes and vitamins C and E were classified as supplemental, nonsupplemental, and total (supplemental plus nonsupplemental). Intakes of vitamin C were measured in grams per day, and carotenes and vitamin E were measured in international units per day. Intakes were transformed using natural logarithm (vitamin E) or square root transformation (calories, carotenes, and vitamin C) to achieve a more normal distribution. Nonsupplemental intakes were adjusted for total caloric intake as recommended by Willett (14) by calculating the residuals from linear regression models (nutrient intake regression on total caloric intake using transformed values for both nutrients and calories) and adding a constant (mean nutrient intake). Nutrient intakes from supplements were not adjusted for total caloric intake. The total nutrient intake was calculated by addition of the calorie-adjusted nonsupplemental intake and the non-calorie adjusted supplemental nutrient intake."
Screening and Diagnosis Detail
National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association Criteria (McKhann 1984)
"Diagnosis of dementia and assignment of specific cause were made by the consensus of a group of neurologists, psychiatrists, and neuropsychologists based on the information gathered at the initial and follow-up visits. The diagnosis of dementia was based on criteria from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (10) and required evidence of cognitive deficits on the neuropsychological test battery as well as evidence of impairment in social or occupational function (score >0.5 on the Clinical Dementia Rating Scale (11)). Diagnosis of AD was based on criteria from the National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) (12)."
Covariates & Analysis Detail
Cox proportional hazards regression
Time scale for proportional hazards model was time in study.
Total caloric intake was adjusted for using the regression residual method (Willett W, Stampfer MJ. Total energy intake: implications for epidemiologic analyses. Am J Epidemiol 1986; 124:17-27).
APOE e4 genotype
Dietary intakes were adjusted for total caloric intake using the regression residual method, while supplemental nutrient intakes were not calorie-adjusted.