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Reference: Rovio, 2005
Cohort: North Karelia Project/FINMONICA/Cardiovascular Risk Factors, Aging, and Dementia
Risk Factor: Physical Activity


Average Follow-up Time Detail
Participants were investigated at midlife either in 1972, 1977, 1982, or 1987. 2,000 randomly selected individuals, age 65–79 years by the end of 1997, were invited for a re-examination during 1998. 1,449 people (72·5%) participated in the re-examination. Data on midlife physical activity were available for 1,935 of the 2000 participants in the study population. Only two of those missing PA data had dementia, not AD.

Exposure Detail
"Leisure-time physical activity was assessed on the questionnaire as follows: “How often do you participate in leisure-time physical activity that lasts at least 20–30 mins and causes breathlessness and sweating?” The six response categories were as follows: (1) daily (n=201), (2) 2–3 times a week (n=580), (3) once a week (n=421), (4) 2–3 times a month (n=250), (5) a few times a year (n=404), and (6) not at all (n=79). A trend test for physical activity including these original categories was of borderline significance (p=0·086). For the current analyses, these categories were dichotomised as follows: “active” people were defined as those who participated in leisure-time physical activity at least twice a week (n=781), and “sedentary” people were defined as those who participated in leisure-time physical activity less than twice a week (n=1154). The cut-off for this dichotomisation was based on earlier1,15 and more conservative16 recommendations for health-promoting physical activity."

Ethnicity Detail
According to other descriptions of the cohort, participants were sampled from the populations of Kuopio and Joensuu in eastern Finland. No information on the ethnic background of participants has been provided.

Screening and Diagnosis Detail
Screening Method:
MMSEMini-Mental State Examination (Folstein 1975)

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 defintion: Dementia via DSM IV

"Cognitive status was determined, and participants who scored 24 or less on the mini-mental state examination19 at the screening phase (n=294) were referred for further examinations, including thorough neurological and cardiovascular examinations and a detailed neuropsychological examination. 61 participants were diagnosed as having dementia according to the Diagnostic and Statistical Manual of Mental Disorders (fourth edition) criteria,20 of whom 48 fulfilled the diagnostic criteria of AD according to National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria.21 The dementia diagnoses of non-participants were derived from patients' records of the local hospitals and primary healthcare centres. The total number of dementia cases increased to 117 (5·9% of the population) when these diagnoses were also taken into account. The analyses concerning AD we restricted to AD diagnoses at re-examination (n=48) to ensure diagnostic accuracy, but we repeated the analyses by including non-participants and AD cases identified by register linkage only (n=76; figure 1)."

Covariates & Analysis Detail
Analysis Type:
Logistic regression

"The main analyses were restricted to participants with no missing data on outcome, physical activity, or any of the covariates. The total number of participants in the analyses for dementia was 1251 (61 cases), and 1239 for AD (48 cases). We also analysed the whole sample (n=1935, including dementia and AD cases identified by register linkage) for which the number of individuals with dementia was 115 (two patients with dementia had missing data on physical activity), and those with AD was 76 (no missing data).

"We also did stratified analyses to assess the effect of APOE ɛ4 carrier status on the relation between leisure-time physical activity and the risk of dementia and AD. The putative multiplicative interaction between leisure-time physical activity and APOE ɛ4 carrier status was then analysed by including an interaction term in the model. The interaction between leisure-time physical activity and sex was analysed in a similar manner."

"Among the APOE ɛ4 carriers, the association between physical activity and AD was significant in all models (table 3), whereas among APOE ɛ4 non-carriers, it was not significant. All possible groupings of physical activity and APOE ɛ4 allele status interaction were also analysed in relation to AD. Compared with the sedentary APOE ɛ4 carrier group, the active APOE ɛ4 carriers had an OR of 0·18 (95% CI 0·05–0·67), the sedentary APOE ɛ4 non-carriers had an OR of 0·30 (0·13–0·71), and the active APOE ɛ4 non-carriers had an OR of 0·22 (0·08–0·60). There was a weak tendency towards a multiplicative interaction between physical activity and the APOE ɛ4 allele status for the development of AD (p=0·12, after adjustments), and the additive interaction term was significant in the model (RERI=0·73, p=0·020), which indicated that APOE ɛ4 may modify the association between physical activity and the odds of AD."

AD Covariates:
Aage
Eeducation
Ggender
ALCalcohol intake
APOE234APOE e2 e3 e4 genotype
BMIbody mass index
LDlocomotor disorders
MImycardial infarction history
SMsmoking status
SHstroke history
SBPsystolic blood pressure
TCtotal cholesterol
§ Covariates for total dementia are different.

TD Covariates:
Aage
Eeducation
Ggender
ALCalcohol intake
APOE234APOE e2 e3 e4 genotype
BMIbody mass index
IDDinterval to disease diagnosis
LDlocomotor disorders
MImycardial infarction history
SMsmoking status
SHstroke history
SBPsystolic blood pressure
TCtotal cholesterol

Follow-up time was also controlled for, and BMI was at midlife. Locomotor disorder includes the presence of at least: rheumatoid arthritis, arthritis, arthropathy, or arthralgia of the joins of the extremities or the back.