More evidence that vascular disease plays a crucial role in age-related cognitive impairment and Alzheimer’s comes from data from participants in the Alzheimer's Disease Neuroimaging Initiative.

The study involved more than 800 older adults (55-90), including around 200 cognitively normal individuals, around 400 people with mild cognitive impairment, and 200 people with Alzheimer's disease. The first two groups were followed for 3 years, and the Alzheimer’s patients for two. The study found that the extent of white matter hyperintensities (areas of damaged brain tissue typically caused by cardiovascular disease) was an important predictor of cognitive decline.

Participants whose white matter hyperintensities were significantly above average at the beginning of the study lost more points each year in cognitive testing than those whose white matter hyperintensities were average at baseline. Those with mild cognitive impairment or Alzheimer's disease at baseline had additional declines on their cognitive testing each year, meaning that the presence of white matter hyperintensities and MCI or Alzheimer's disease together added up to even faster and steeper cognitive decline.

The crucial point is that this was happening in the absence of major cardiovascular events such as heart attacks, indicating that it’s not enough to just reduce your cardiovascular risk factors to a moderate level — every little bit of vascular damage counts.