The drug’s benefits increased on larger doses, and had an additive effect when taken with another type of high blood pressure drug, ACE inhibitors.
The team concluded, “Angiotensin receptor blockers are associated with a significant reduction in the incidence and progression of Alzheimer’s disease and dementia compared with other cardiovascular drugs.”
They added that the lower rate of admission to a nursing home “is a particularly important observation that could have a major impact on public health if validated by future studies.”
Dr. Colleen Maxwell and Dr. David Hogan of the University of Calgary, Canada, write in an accompanying editorial that the drugs may cause “improved cerebral blood flow and an enhanced neuroprotective effect.” But two randomized controlled trials have found “no significant benefit in either the rate of cognitive decline or incident dementia.”
They warn that important factors such as a family history of dementia, education, and severity of disease were not considered, and the “non-random allocation of treatment” is also a serious problem. Racial and ethnic variation in the use of drugs such as these has been shown among American veterans, and the ethnic origin of most participants was not reported. Furthermore, the results may not be generalizable to women, because women comprised only two percent of participants.
“As with all studies of this nature, association does not prove causation. Further work is needed to verify the usefulness of antihypertensives in general and angiotensin receptor blockers in particular,” they conclude.
A previous study by Professor Wolozin’s team reported that simvastatin, a cholesterol-lowering drug, is linked to a reduction in the risk of dementia and Parkinson’s disease. The study also used figures on more than 70,000 people from the database of the U.S. Veteran Affairs.
However, a more recent review, from 2010, states, “There is good evidence from randomized controlled trials that statins given in late life to individuals at risk of vascular disease have no effect in preventing Alzheimer’s disease or dementia.
“Biologically it seems feasible that statins could prevent dementia due to their role in cholesterol reduction and initial evidence from observational studies was very promising. [But] the evidence from subsequent randomized controlled trials has been negative.”
So far, say the authors of this Cochrane review, there is insufficient evidence to recommend statins for the prevention treatment of dementia.
Dr. Mary N. Haan of the University of California, San Francisco points out that there have not been any randomized clinical trials of initially healthy individuals that were expressly designed to test whether statins can prevent dementia.
“It is now recognized that dementia begins to develop decades before it is symptomatic,” she writes in the journal Evidence Based Mental Health. “Thus to design an adequate prevention trial for dementia requires a relatively young study sample, a large sample and substantial follow-up time.”
She believes that, “At this juncture, it is not possible to conclude that statins could or could not prevent dementia.”
Li, N-C. et al. Use of angiotensin receptor blockers and risk of dementia in a predominantly male population: prospective cohort analysis. The British Medical Journal, 2010;340:b5465.
Maxwell, C. J. and Hogan, D. B. Antihypertensive agents and prevention of dementia. The British Medical Journal, 2010;340:b5409.
Wolozin, B. et al. Simvastatin is associated with a reduced incidence of dementia and Parkinson’s disease. BMC Medicine, published online July 19, 2007.
McGuinness, B. et al. Statins for the treatment of dementia. Cochrane Database of Systematic Reviews, August 4, 2010.
McGuinness, B. et al. Statins for the prevention of dementia. Cochrane Database of Systematic Reviews, April 15, 2009.
Haan, M. N. et al. Review: statins do not protect against development of dementia. Evidence Based Mental Health, Vol. 12, November 2009, p. 114.