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AlzRisk Paper Detail

Reference: Laurin, 2001
Cohort: Canadian Study of Health and Aging
Risk Factor: Physical Activity

Average Follow-up Time Detail
These figures pertain to the analysis of total dementia, but are expected to be reasonably similar for the analysis of AD.

The first wave of the study was conducted in 1991-1992 (CSHA-1). All subjects without dementia reported requested information via a self-administered risk factor questionnaire. Follow-up was carried out in 1996-1997 (CSHA-2). Among those eligible in CSHA-1 without dementia, 1,172 (18%) died during follow-up and 647 (10%) did not participate in CSHA-2. The decedents and nonrespondents were older, less educated, and less physically active at baseline than the control group. They appeared more similar to the group with dementia or cognitive impairment-no dementia at CSHA-2.

Exposure Detail
"Exercise data were collected as part of CSHA-1 when subjects were not demented and represent a proxy for earlier activity up until the time of baseline. The level of physical activity was assessed by combining 2 questions from the risk factor questionnaire regarding frequency and intensity of exercise for subjects who reported regular physical activity. A composite score rating physical activity as either low, moderate, or high, was obtained by summing answers to the frequency question (>3 times per week, weekly, or less than weekly) and the intensity question (more vigorous, equal to, or less vigorous than walking). A high level of physical activity corresponded to an exercise engaged 3 or more times per week at an intensity greater than walking, while a moderate level of physical activity corresponded to exercise also engaged 3 or more times per week, but of an intensity equal to walking. All other combinations of frequency and intensity were considered as a low level of physical activity. Subjects who reported no regular exercise constituted the reference category. The measurement properties of this index were assessed with an independent sample of 738 elderly individuals, to whom the risk factor questionnaire was administered by an interviewer. Construct validity was assessed by comparing the combined score with other reported markers of health hypothesized to be related to exercise and self-rated health. The average intraclass coefficient for the combined score was 0.76 (95% confidence interval [CI], 0.72-0.79; P = .002), while the combined score demonstrated satisfactory construct validity, and seemed to be well associated with mortality over 5 years.57"

Ethnicity Detail
Not reported. The cohort is a representative sample of Canadian men and women aged 65 and older living in urban and rural Canada from all 10 provinces.

Age Detail
Participants were 65 years or older at baseline. At baseline, 54% of the population was between ages 65-74, 39% were between 75-84, and 7% were greater than 84.

Screening and Diagnosis Detail
Screening Method:
3MSEModified Mini-Mental State Examination (Teng 1987)

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

Total dementia definition: Total dementia defined as AD, vascular dementia, and other specific and unclassifiable dementia. Dementia diagnosed via DSM IV, vascular dementia via NINDS-AIREN.

"Participants were screened for dementia using the Modified Mini-Mental State (3MS) Examination.47,48 Subjects who screened positive (3MS Examination score <77), and a random sample of those who screened negative (3MS Examination score >78) were asked to attend an extensive standardized 3-stage clinical evaluation.49 A nurse first screened for hearing and vision problems, and collected information about medication regimen and medical and family histories. Next, a physician carried out standardized physical and neurologic examinations. Third, a psychometrist administered a neuropsychological test battery50 to all individuals deemed testable (3MS Examination score >50), the results of which were interpreted by a neuropsychologist. Preliminary diagnoses were made independently according to Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition criteria51 by the physician and the neuropsychologist who subsequently arrived at a diagnosis in a consensus conference. Consensus diagnoses constituted the following: no cognitive impairment, cognitive impairment–no dementia [CIND],52 Alzheimer disease (probable or possible) according to NINCDS-ADRDA (National Institute of Neurological Disorders and Stroke–Alzheimer's Disease and Related Disorders Association) criteria,53 vascular dementia according to World Health Organization International Classification of Diseases, 10th Revision criteria,54 other specific dementia and unclassifiable dementia. All subjects without dementia were asked to complete and return by mail a self-administered risk factor questionnaire covering specific expositions for which prior hypotheses existed. This questionnaire included questions about demographic characteristics, occupational and environmental exposures, lifestyle, and medical and family histories.

"Follow-up was carried out in 1996-1997 (CSHA-2). All subjects who could be contacted and who agreed to participate in the second wave were reinterviewed to measure changes in health status and functioning following a 5-year period on average. Subjects took part in the same diagnostic process as in CSHA-1, including screening and clinical evaluation. Diagnoses from consensus conferences in CSHA-2 were made without knowledge of CSHA-1 diagnoses. Two final diagnoses were made for dementia and vascular dementia, one according to the same criteria used in CSHA-1, and the other according to more recent Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition55 and NINDS-AIREN (National Institute of Neurological Disorders and Stroke–Association Internationale pour la Recherche et l'Enseignement en Neurosciences) criteria.56"

Covariates & Analysis Detail
Analysis Type:
Logistic regression

"Five separate analyses were performed to assess the associations between exercise and incident cognitive loss, CIND, Alzheimer disease, vascular dementia, and any type of dementia. Univariate and multivariate logistic regression models were used to analyze the crude and adjusted odds ratios (ORs) for the 5 end points.

"Modification of risk by age, sex, education, and family history of dementia was investigated using interaction terms. {chi}2 Tests for linear trend were performed using the 4-level physical activity variable as an ordinal variable in adjusted models."

No interaction was found with age, education, or family history of dementia and regular physical activity.

AD Covariates:

TD Covariates:

Age and education were entered as continuous variables.