ACE inhibitors and dementia: radiation protection?

These kind of loose association studies are a dime a dozen, and usually misleading. They're digging data obtained for other reasons to look for an association. What makes it interesting, however, is the animal study:

Some heart drugs may slow mental decline with age | Health | Reuters:

... The study found a link between taking these "centrally acting" ACE inhibitors and lower rates of mental decline as measured by the Modified Mini-Mental State Exam...

For each year that subjects were exposed to centrally acting ACE inhibitors that enter the brain, the decline in test results was 50 percent lower than the decline in people taking other kinds of high blood pressure pills...

... Centrally acting ACE inhibitors include captopril (Capoten), fosinopril (Monopril), lisinopril (Prinivil or Zestril), perindopril (Aceon), ramipril (Altace) and trandolapril (Mavik). [jf: several of these are off-patent now]

Sink decided to investigate the effect of centrally acting ACE inhibitors on dementia risk after her Wake Forest colleagues found the drugs protected rats from brain injury due to radiation. She presented her findings May 5 at the American Geriatrics Society's annual meeting in Seattle.

She and her colleagues looked at a subgroup of 1,074 men and women participating in a study of cardiovascular health who were taking drugs to treat hypertension and were dementia-free when the study began.

While the centrally acting ACE inhibitors did slow cognitive decline, as Sink had hypothesized, the non-centrally active ACE inhibitors that don't reach the brain actually boosted the risk of developing dementia by 20 percent, although the effect didn't reach statistical significance....

The radiation protection effect is what made my ears perk up. The rest of this is thin stuff, enough only to justify further work. We do have animal models for dementia, so that is the place to look next. The "risk increase" numbers are probably random error in this type of study.