Nighttime Blood Pressure Interacts with APOE Genotype to Increase the Risk of Incident Dementia of the Alzheimer's Type in Hispanics.

BACKGROUND: Dementia of the Alzheimer's type (DAT) impacts Hispanics disproportionately, with almost a twofold elevated risk of developing DAT, as well as earlier onset of the disease, than in non-Hispanic Whites. However, the role of main risk factors for DAT, such as APOE-ɛ4 and blood pressure (BP) levels, remains uncertain among Hispanics. OBJECTIVE: To investigate the association of APOE-ɛ4 and BP levels, measures with 24-h ambulatory BP monitoring, with incidence of DAT in an elderly cohort of Hispanics. METHODS: 1,320 participants from the Maracaibo Aging Study, free of dementia at the baseline, and with ambulatory BP measurements and APOE genotype available were included. Adjusted Cox proportional models were performed to examine 1) the incidence of DAT and 2) the relationship between BP levels and DAT according to APOE genotypes. Models were adjusted by competing risk of death before the onset of DAT. Model performance was assessed by likelihood test. RESULTS: The average follow-up time was 5.3 years. DAT incidence was 5.8 per 1000 person-year. APOE-ɛ4 carriers had a higher risk of DAT. In unadjusted analyses, conventional, 24-h, and nighttime systolic BP levels were significantly higher in participants who developed DAT and of APOE-ɛ4 carriers (p < 0.05). After adjustment for competing risks, only higher nighttime systolic BP was associated with DAT incidence, but only among subjects carrying APOE-ɛ4. CONCLUSION: In this Hispanic population, both APOE-ɛ4 genotype and assessment of nocturnal systolic BP (rather than diurnal or office BP) were necessary to estimate DAT risk.

The Maracaibo Aging Study: population and methodological issues.

The Maracaibo Aging Study is a longitudinal, population-based, one-step multidisciplinary study of age-related diseases, with a particular focus on memory-related disorders, among subjects over 55 years living in a neighborhood of the city of Maracaibo, Venezuela. Three phases were scheduled for this study. First, a door-to-door survey was conducted in order to build a registry and to obtain general and sociodemographic characteristics. During the second phase, information regarding changes in the abilities of the subjects was collected. The third phase consisted of a full neuropsychiatric examination, cardiovascular evaluation, nutritional assessment, neuropsychological testing, routine laboratory tests and genetic analysis. 3,657 subjects were surveyed between January and August, 1998. There were more women than men, and the average number of years of formal education was low, particularly among women. The limitations and strengths of the study are discussed.