APOE genotype, cardiovascular risk, and incident dementia in the Norwegian HUNT study.

Apolipoprotein E (APOE) genotype and cardiovascular risk are both associated with dementia, but their separate and joint contributions remain uncertain. We examined the independent and combined associations of APOE genotype and cardiovascular disease (CVD) risk with incident dementia in a Norwegian populationbased cohort. In this prospective cohort study, baseline data were obtained from the second Trøndelag Health Study (HUNT2, 1995-97), with follow-up through linkage to specialist health-care records and the Norwegian Cause of Death Registry through Dec 31, 2023. We included 22,108 participants aged 50 years or older who were free of CVD, diabetes, and dementia at baseline. APOE genetic risk and cardiovascular risk based on SCORE2 were each classified into three categories. Adjusted hazard ratios (HRs) for incident dementia were estimated using Cox models. During a median follow-up of 22.0 years, 3,714 incident dementia events occurred. Compared with low APOE genetic risk, adjusted HRs were 1.25(95% CI1.10-1.41) for intermediate risk and 3.09(2.73-3.49) for high risk. Compared with low-to-moderate CVD risk, adjusted HRs were 1.19(1.07-1.32) for high risk and 1.36(1.19-1.55) for very high risk. In joint analyses, the highest risk was observed in participants with high APOE genetic risk and very high cardiovascular risk (HR 3.78, 2.85-5.01). Higher cardiovascular risk was more clearly associated with dementia in participants without high APOE genetic risk, whereas dementia risk was consistently elevated across cardiovascular risk categories among those with high APOE genetic risk. There was no clear evidence of multiplicative interaction (p=0.059). APOE genotype and cardiovascular risk were independently associated with incident dementia, with highest risk among individuals with both high genetic and cardiovascular risk.