Alzheimer's Disease Course Project Part Research Paper

g., demented vs. nondemented) were evaluated using the Pearson ?2 test. Levels of tHcy, vitamin B12, and folate were log-transformed to fit normal distributions. Odds ratios (ORs) and 95% confidence intervals (CI) were calculated using two logistic regression models."

Chance: Low, given the long-term screening of subjects for AD in larger Maracaibo Aging Study

Generalizability

Eligible population: Patients with a strong genetic predisposition for AD

Source population: Uncertain, given the diverse range of factors that could still affect the health of the source population, although many common risk factors were accounted for in the statistical analyses performed

Other population: Generalizability between the Maracaibo population and the AD population as a whole is still being determined.

Study 3:

Bowirrat A; R.P. Friedland; L. Farrer, C. Baldwin, A. Korczyn. (2002). Genetic and environmental risk factors for Alzheimer's disease in Israeli Arabs.

Journal of Molecular Neuroscience, 19(1-2):239-45.

Causality Criteria

Description: An assessment of genetic and environmental risk factors and prevalence, and incidence of dementia of the Alzheimer type (DAT) among the elderly in an Arab community in Israel.

Exposure, Intervention: All persons aged 60 years or older who were residents of the rural area of Wadi Ara were examined for identification of dementia associated with Alzheimer's disease (DAT), vascular dementia (VaD) and age related cognitive decline (ARCD) due to AD. DSM-IV criteria and a semi-structured questionnaire were used. "ApoE genotype was also determined.Total plasma homocysteine (tHcy) was determined using HPLC with fluorescence detection. Vitamins B12 and plasma folate were determined using a commercial radioisotope dilution kit assay (ICN)."

Study design: Descriptive

Study Population: Residents of remote Arab village

Main Result: DAT (dementia of the Alzheimer's type) was diagnosed in 20.5% of this population. Illiteracy, old age, and female strongly correlated with development of AD. "The ApoE epsilon4 allele is relatively uncommon in this population and it cannot explain the high DAT prevalence." But it was similarly found that vascular-related dementia and age related-dementia were also correlated.

Internal Validity

Observation bias: Possible observational bias given open-ended nature of questionnaires and difficulty of determining cause of dementia

Recall bias: Questionnaires described as semi-structured, leading to possible bias

Confounding: "ApoE genotype was also determined. Total plasma homocysteine (tHcy) was determined using HPLC with fluorescence detection. Vitamins B12 and plasma folate were determined using a commercial radioisotope dilution kit assay (ICN)."

Chance: High, given singularity of test population.

Generalizability

Eligible population: All residents of remote Israeli Arab village

Source population: Uncertain, particularly given the subjective nature of the causality of the different dementias studied

Other population: Points to need for further examination of relationship of illiteracy….....