Statins have no impact on the development of dementia or Alzheimer's disease, according to a Cochrane Review of two randomized, controlled trials involving more than 26,000 adults.
Previous studies in animal models have shown that lowering cholesterol slows pathologic signs of Alzheimer's disease (AD), and data from clinical studies in older adults who took statins for vascular disease have suggested that statin users had a reduced risk of developing AD. But the clinical studies in humans were not randomized trials, said Dr. Bernadette McGuinness of Queen's University Belfast, Northern Ireland.
In this review, Dr. McGuinness and her colleagues examined data from two large, randomized controlled trials that included 26,340 adults aged 40-82 years (Cochrane Database Syst. Rev. 2009 April 15; doi: 10.1002/14651858.cd007514
The Medical Research Council/British Heart Foundation Heart Protection Study (HPS) conducted in 2002 was a randomized, placebo-controlled trial of the effect of a daily dose of 40 mg simvastatin vs. placebo on the development of vascular disease in 20,536 high-risk adults, including 5,806 adults aged 70 years and older.
Cognitive decline was assessed via a questionnaire completed in person at the clinic or by phone. No significant differences appeared between the treatment and placebo groups in the overall percentages of patients who met criteria for cognitive impairment at the start of the study (23.7% vs. 24.2%). And 31 individuals in each group developed dementia during a 5-year follow-up period (Lancet 2002;360:7-22).
In another 2002 study, the Prospective Study of Pravastatin in the Elderly at Risk (known as the PROSPER trial), 5,804 adults aged 70-82 years were randomized to receive a daily dose of 40 mg pravastatin or a placebo. All the study participants had risk factors for vascular disease or a history of vascular disease. The cognitive function of the participants was assessed using neuropsychologic tests and the Mini-Mental State Examination. During a 3-year follow-up period, pravastatin had no significant impact on cognitive function (Lancet 2002;360:1623-30).
“The two trials identified were large scale and included patients at high risk of vascular disease,” noted the researchers, who had no relevant conflicts of interest to disclose. “The fact that they had similar findings was reassuring.”