A new study has shown that higher levels of good cholesterol are linked to an increased risk of Alzheimer’s disease. The study also revealed that it depends on the quality, rather than quantity, of the total cholesterol carried by HDL (high-density lipoproteins) particles circulating in a woman’s blood. The study was published in the Journal of Clinical Endocrinology and Metabolism.

Cholesterol is a waxy, fat-like substance produced by the liver. This plays a major role in the formation of cell membranes and Vitamin D. However, cholesterol cannot travel through the body by itself because it doesn’t dissolve in water. There are particles called lipoproteins which help in the movement of cholesterol through the bloodstream.

The two types of lipoproteins lead to the two different types of cholesterol. Low-density lipoprotein (LDL) is the one bad cholesterol which eventually causes high cholesterol. On the other hand, high-density lipoprotein (HDL) is the good cholesterol which helps in maintaining cholesterol levels. The good cholesterol helps in returning the bad cholesterol to the liver from where it can be removed. When your LDL is higher than HDL, it leads to fat deposition in the blood vessels.

The study explained that once women reach the menopause transition, it’s a matter of quality, rather than quantity. The researchers from the University of Pittsburgh in the US found that over time, the number of larger HDL particles in women’s bodies increased. These larger particles, unfortunately, did not function as well as their smaller counterparts.

Samar R. El Khoudary, professor of epidemiology at Pitt Public Health said, “We were able to show that as early as midlife, women who have more of the smaller-sized particles and those whose particles’ concentrations of phospholipids increased over the menopause transition are more likely to experience better episodic memory later in life.”

The loss of working memory is the first sign of Alzheimer’s disease. HDL particles vary in their size, composition and level of functioning. During the study, the researchers conducted repeated assessments of participants’ cognitive function from 2000 to 2016 and compared these data to changes in the women’s HDL particles, composition and function as they aged.

The team has previously shown that health behaviours work to improve the quality of HDL particles, for example by adding more of the phospholipid-rich particles in the bloodstream. El Khoudary said, “That’s the good news in this developing picture of brain health and the ‘not-so-good-after-all’ cholesterol.”

Even though higher levels of HDL-C may not be protective as you get older and there are things you can do that might help, even as early as your 40s, the researchers advised.

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