When we speak of cholesterol, negative thoughts of blocked arteries and heart attacks come to mind. However, not all types of cholesterol are detrimental to our health. There are 2 main types of cholesterol in our body – the low-density lipoproteins (LDL) and the high-density lipoproteins (HDL). LDL cholesterol is considered to be “bad” cholesterol and is linked to atherosclerosis. LDL levels in our blood should therefore be kept low. HDL is deemed to be the “good” cholesterol and high levels of HDL in the blood may actually be beneficial and decrease the risk of heart attacks. HDL cholesterol plays important roles in several vital biological functions including clearance of excess cholesterol from the blood, assistance in the maturation process of nerve-cell synapses, and controlling the formation of beta-amyloid. Beta-amyloid is the major component of plaque deposits found in the brains of patients with Alzheimer’s disease.
A recent study demonstrated the role of HDL in the development of dementia. Low levels of HDL are linked to having memory loss in middle age and dementia later in life. The report is based on data collected by the Whitehall II study, a long-term health research study involving more than 10,000 British civil servants working in London. The study has been ongoing since 1985.
The research defined low HDL levels as less than 40 mg/dL and high HDL levels as 60 mg/dL or more. The researchers analysed blood-fat and memory data collected during 2 phases of Whitehall II. Phase 5 was conducted from 1995 to 1997 and involved study participants with an average age of 55. Phase 7 was conducted from 2002 to 2004 and involved participants with an average age of 61 years.
The main findings of study are as follows:
- • At age 55, participants with low HDL cholesterol showed a 27 percent increased risk of memory loss when compared to those with high HDL.
- • At age 60, participants with low HDL had a 53 percent increased risk of memory loss compared to the high HDL group.
- • During the five years between phases 5 and 7, study members with decreasing HDL had a 61 percent increased risk of decline in their ability to remember words versus those with high HDL.
- • Men and women did not differ significantly in the link between lipids and memory loss, so researchers combined data from both sexes for analysis.
- • Total cholesterol and triglycerides did not show a link with memory decline.
- • Using statin drugs to raise HDL and/or lower low-density lipoprotein (LDL or “bad” cholesterol) showed no association with memory loss.
In the industrialized world, where the population is aging, dementia is becoming a major concern. People 65 years or older are the ones who are usually affected. For a quick review of dementia, check this previous post.