Both high levels of LDL ("bad") cholesterol and low levels of HDL ("good") cholesterol have been linked with memory loss and dementia in clinical studies. In addition, anecdotal reports have raised the possibility that some treatments for high cholesterol may be linked with memory loss, although this relationship is unclear.
Bad Cholesterol and Memory
In a 2002 study in the Archives of Neurology, Yaffe and colleagues found that among 1,037 older women followed for four years, those with elevated total and LDL cholesterol scored lower on a test measuring their ability to concentrate, remember, and reason than those with normal cholesterol levels. Women with the highest cholesterol levels were almost twice as likely to show signs of memory loss compared with women with low cholesterol levels. Women whose cholesterol levels remained steady or declined during the study period were half as likely to experience memory problems as those whose cholesterol levels increased over time. In this study, HDL and triglyceride levels were not associated with memory loss.
Good Cholesterol and Memory
In another study published in 2008 in Arteriosclerosis, Thrombosis and Vascular Biology, Singh-Manoux and colleagues found that decreasing levels of HDL cholesterol predicted declining memory by age 60. The study involved 3,673 subjects. At age 55, study subjects with low HDL cholesterol exhibited a 27 percent increased risk of memory loss compared with subjects with high HDL levels. By age 60, subjects with low HDL had a 53 percent increased risk of memory loss. Total cholesterol and triglycerides were not associated with memory loss.
Statin Treatment and Memory
Statins are a widely used treatment for high cholesterol. Wagstaff and colleagues reviewed 60 case reports from the medical literature of memory loss in patients using statins. They found that the literature is conflicting and that a causal link between statin use and memory impairment cannot be made with certainty, although they allow that such a link is possible.
Lowering Cholesterol and Dementia Risk
These studies suggest that lowering bad cholesterol levels and perhaps increasing good cholesterol levels may prevent dementia in some patients. Indeed, patients treated with statins have been shown to have a lower dementia risk in a number of studies cited by Wagstaff and colleagues.
Other Risk Factors for Memory Loss
Patients with high cholesterol may have other risk factors for memory loss as well, including advancing age and other cardiac conditions. Cerebrovascular disease is known to be associated with memory loss.
