About 15 million Americans take statins, a type of medication that helps to lower cholesterol. Yet, when a group of Johns Hopkins researchers investigated whether statins produce cognition problems, they discovered astounding evidence of the exact opposite: statins, when taken for a year or more, may reduce the risk of dementia by 29 percent.
"Our systematic review and meta-analysis of existing data found no connection between short-term statin use and memory loss or other types of cognitive dysfunction,” Kristopher Swiger, M.D., a primary author of the study, stated in a press release. “In fact, longer-term statin use was associated with protection from dementia."
To investigate the matter, the researchers conducted a systematic review of dozens of studies on the use of statin medications. After analyzing a total of 41 different studies, they winnowed the pile down to the 16 most relevant to their investigation. First, they considered the impact of short-term statin use and cognitive function, in particular how the medication might effect memory, attention, and problem-solving; included in this analysis were studies employing a standard, objective measurement tool known as the Digit Symbol Substitution Test. A second assessment highlighted studies in which participants took statins for more than one year. The researchers searched for any correlations between medication use and a later diagnosis of Alzheimer's disease or vascular dementia.
"We looked at high-quality, randomized controlled trials and prospective studies that included more than 23,000 men and women with no prior history of cognitive problems,” Raoul Manalac, M.D., a co-primary author of the study, stated in a press release. “The participants in those studies were followed for up to 25 years."
Why are Statins Prescribed?
Cholesterol is a waxy, fat-like substance found in the blood. Although the body requires cholesterol to build cells, high cholesterol may cause fatty deposits to build up on the walls of blood vessels. In turn, these deposits make it difficult for enough blood to flow through the arteries. When the heart fails to get enough oxygen-rich blood, the risk of a heart attack increases; when the brain fails to get enough blood flow, the risk of a stroke increases.
The Centers for Disease Control and Prevention reports that roughly a third (71 million, or 33.5 percent) of American adults have too high levels of low-density lipoprotein (LDL). Low-density lipoprotein, commonly referred to as LDL, is "bad" cholesterol while high-density lipoprotein, or HDL, is "good" cholesterol. LDL can form deposits in the arteries and slow blood flow, while high levels of HDL seem to carry bad cholesterol to the liver where it is passed from the body. In so doing, HDL may even protect against heart disease.
Statin medications, then, reduce cholesterol levels, particularly LDL cholesterol, in the blood. In studies, the drugs have been shown to reduce the amount of inflammation within blood vessels and prevent the risk of blood clots.
"Because of their effect on arteries to reduce or stabilize plaque, and prevent strokes, it makes sense that statins could be protective in the brain against dementia," Seth Martin, M.D., of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease and the study's senior author, stated in a press release. "Vascular dementia is caused by blockages in small blood vessels in the brain that prevent blood flow to certain areas. Medications such as statins that reduce plaque and inflammation in coronary arteries may also be having the same effect on blood vessels in the brain."
Patients and cardiologists began to question whether statins caused cognition problems following changes on the drug label warnings about memory problems with short-term statin use. The changes had been ordered by the U.S. Food and Drug Administration (FDA) in Feb. 2012 to address reports of memory loss and confusion when using statins. “These reported events were generally not serious and went away once the drug was no longer being taken,” the FDA said, addressing the label change.
"Our goal was to provide clarity on this issue based on the best available evidence," Manalac stated in a press release.
Source: Manalac R, Martin S, Swiger K, et al. Statins and Cognition: A Systematic Review and Meta-analysis of Short- and Long-term Cognitive Effects. Mayo Clinic Proceedings. 2013.