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-epsilon 4 and blood pressure (BP) levels, remains uncertain among Hispanics. Objective: To investigate the association of APOE-epsilon 4 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-epsilon 4 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-epsilon 4 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-epsilon 4. Conclusion: In this Hispanic population, both APOE-epsilon 4 genotype and assessment of nocturnal systolic BP (rather than diurnal or office BP) were necessary to estimate DAT risk.