Early studies led to excitement in the dementia field about the possible link between the cholesterol-lowering drugs known as statins and dementia prevention. But later studies did not draw such promising conclusions.
Lancet Study Shows Decreased Dementia Risk
In November 2000, a study published in the Lancet found that individuals over the age of 50 who were prescribed statins had a substantially lowered risk of developing dementia. The researchers compared 284 people who had dementia ("cases") with 1,080 "controls" who did not. This type of study is known as a case-control study. Those individuals who were prescribed statins had a much lower risk compared with those who were not prescribed statins, even after factors like age, gender, and history of heart disease were taken into account. The results were highly statistically significant.
Further Studies Refute Theory of Statins and Dementia Prevention
Although a second study published in 2004 found that statin users had a 39% lower risk of Alzheimer's disease compared with non-statin users, this too was a case-control study. So do these two studies mean that statins lower the risk of Alzheimer's disease? Unfortunately not.
Two large studies of statins in people at risk of Alzheimer's and other dementias have now been conducted, involving a total of 26,340 participants. These were both double-blind randomized placebo-controlled trials, the most authoritative type of study. Because case-control studies look back in time and are not randomized, the conclusions that can be drawn from them are limited. Double-blind studies look forward in time, are organized so that the study investigators don't know which patients are getting drug and which are getting placebo, and are much better suited to showing cause and effect relationships.
Patients in the first double-blind study were followed for an average of 3.2 years, and those in the second study for five years. The cognitive function of people in the first study declined at the same rate. And in the second study, there was no difference in the incidence of dementia between subjects who got a statin versus those who got a placebo.
Given the strength of these later studies, the evidence to conclude that statins prevent Alzheimer's or other dementias is much less clear.
Jick H, MD, Zornberg GL, MD, Jick SS, DSc, Seshadri S, MD, Drachman DA, MD. "Statins and the Risk of Dementia."The Lancet 2000 vol. 356, Issue 9242: 1627-31.
McGuinness B, Craig D, Bullock R, Passmore P. "Statins for the Prevention of Dementia". Cochrane Database of Systematic Reviews 2009, Issue 2.
Zamrini E, McGwin G, Roseman J. "Association Between Statin Use and Alzheimer's Disease". Neuroepidemiology 2004; 23:94-98.