From the article:
Based on evidence that hypertension was associated with Alzheimer’s disease, Rodrigue suspected that the combination of hypertension and the presence of the APOE-e4 gene might lead to particularly high levels of amyloid plaque in healthy adults.
[…]
The most striking result of the study was that nonmedicated hypertensive adults who also carried a genetic risk factor for Alzheimer’s disease showed much higher amyloid levels than all other groups. Adults with medication-controlled hypertension, even those with genetic risk, had levels of amyloid plaque equivalent to participants without hypertension or genetic risk.