Low cholesterol and Alzheimer's disease

Alzheimer’s disease makes up 55% of dementia cases in the UK, according to the Alzheimer’s Society and over 800,000 people in the UK currently suffer the affliction.

It is argued by some that the recent growth in numbers of people succumbing to Alzheimer’s disease may be because it is a disease of the elderly and people are living longer. But that theory doesn’t stand up to scrutiny as Alzheimer’s is increasingly seen in younger people. It is also seen in people with other conditions known to be caused by an incorrect ‘healthy’ diet such as diabetes; and the number of people with Alzheimer’s has more than doubled since 1980.

The low cholesterol we are all supposed to strive for is a likely cause of this increase in Alzheimer’s disease. Work in the 1950s found that as we get older, the level of cholesterol in our brains declines.[1] Later studies suggested that this decline may be the cause of brain disorders such as Alzheimer’s.

In 1991, a paper discussing the relief of Alzheimer’s Disease, asked that ‘strategies for increasing the delivery of cholesterol to the brain should be identified’ and recommended increasing fat intake.[2]

The Framingham Study added weight to this proposition when it examined the relationship between total cholesterol and cognitive performance.[3] Participants were 789 men and 1105 women who were free of dementia and stroke and who received biennial cholesterol checks over a 16- to 18-year surveillance period. Cognitive tests were administered four to six years after the surveillance period and consisted of measures of learning, memory, attention, concentration, abstract reasoning, concept formation, and organizational abilities.

The researchers found a significant linear association between the level of blood cholesterol and measures of verbal fluency, attention, concentration, abstract reasoning, and a composite score measuring multiple cognitive domains. Participants with ‘desirable’ cholesterol levels of less than 5.2 mmol/L (200 mg/dL) performed significantly less well than participants with cholesterol levels higher than 6.25 mmol/L (240 mg/dL). Dr. Penelope K. Elias from Boston University said that:

‘It is not entirely surprising that lower cholesterol levels were associated with moderately lower levels of cognitive function, given [that] cholesterol is important in brain function.’

"Initial use of statins resulted in less cognitive decline in individuals, but continued use of a statin resulted in more cognitive decline."(emphasis added)