Interactive effect of APOE genotype and blood pressure on cognitive decline: the PATH through life study

The apolipoprotein E (APOE) *ε4 allele and hypertension are two of the most prevalent risk factors for cognitive decline in later life. Here we investigate whether cognitive decline is affected by interaction between these two risk factors. Specifically, we examine whether APOE*ε4 moderates the association between high blood pressure and cognition in later life. Cognitive function was assessed at three time points over a period of 8 years in 1,474 cognitively normal, community-dwelling adults aged 60-64 years at baseline. Blood pressure and APOE genotype were assessed at baseline. Blood pressure was measured categorically as 'Hypertension' and continuously as 'Mean Arterial Pressure' (MAP). Multilevel models were used to investigate main and interactive effects of APOE genotype and both hypertension and MAP on the rate of change of episodic memory, working memory, verbal ability, perceptual speed, and global cognition. The APOE-hypertension interaction was associated with a small but statistically significant increase in the rate of decline of episodic memory, verbal ability, and global cognition. However, its inclusion in the model did not increase the amount of outcome variation explained beyond that already explained by the effect of time. In contrast, the APOE-MAP interaction had no effect on the rate of decline in any of these domains of cognitive performance. These results provide tentative evidence that APOE genotype moderates the association between high blood pressure and cognitive decline in later life.