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AlzRisk Paper Detail

Reference: Li, 2010
Cohort: Adult Changes in Thought-Group Health Cooperative
Risk Factor: Statin use

Exposure Detail
The interviewers ascertained exposure data from computerized pharmacy records, which included information on drug, dosage, quantity dispensed, prescription date, and instructions.

"GHC patients receive prescriptions through the GHC pharmacy at no or nominal cost. The GHC pharmacy database was established in January 1977. Its data files contain information on drug, dosage, quantity dispensed, prescription date, and instructions. Use of statin medications (simvastatin, lovastatin, pravastatin, and atorvastatin) and other lipid-lowering agents (LLAs), including niacin,cholestyramine, colestipol, gemfibrozil, and clofibrate, was defined as at least three filled prescriptions for statins or LLAs of 15 tablets or more. Subjects who did not use statins consistently with average daily dose (cumulative dose/duration <0.5 and total number of refills <12) were considered nonusers. To quantify statin use, an approximation of one ‘‘statin equivalent dose’’ of 10mg of simvastatin, 20mg of lovastatin or pravastatin, or 5mg of atorvastatin was used. Duration of statin use was defined as the time elapsed from the date of first statin prescription to the date of last prescription."

The investigators compared incident AD risk in two groups: the group of participants who used statins, as defined above ("Used") and the reference group of participants who did not use statins consistently, also as defined above ("Did not use").

Screening and Diagnosis Detail
Screening Method:
CASICognitive Abilities Screening Instrument (Teng 1994)
Neuropsych Testing

AD Diagnosis:
DSM IV Diagnostic and Statistical Manual IV
NINCDS ADRDA National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association Criteria (McKhann 1984)

Total Dementia Definition: Dementia via DSM-IV clinical criteria

"After enrollment, participants were re-screened every 2 years using the CASI. Those whose CASI scores were lower than 86 underwent a standardized dementia diagnostic evaluation that included examination by a study physician and neuropsychological tests. Relevant laboratory tests and neuroimaging studies were performed, or results were obtained from GHC records. Diagnoses were assigned at consensus diagnostic conferences using Diagnostic and
Statistical Manual of Mental Disorders, Fourth Edition, criteria for dementia and National Institute of Neurological and Communicative Disorders and Stroke Alzheimer Disease and Related Disorders Association (NINCDS-ADRDA) criteria for AD. Those with new-onset dementia underwent at least one annual follow-up examination for verification of dementia status and subtype. Dementia onset was defined according to convention as halfway between the date of diagnosis and the date of the prior ACT study examination that showed no dementia."

Covariates & Analysis Detail
Analysis Type:
Cox proportional hazards regression

Researchers stratified the analysis by five-year categories of age and by APOE-e4 status. Age was used as the time-scale

AD Covariates:
APOE4APOE e4 genotype
CASIbaseline CASI score
BMIbody mass index
CMVDcomorbid vascular disease
LLAother lipid lowering agent use
SMsmoking status