2023-07-12 04:00:00
Many studies had already identified this fatty substance as a risk factor, but the impact of fluctuations in its level during life was less certain.
Cholesterol is a multifaceted substance. Much more than a cardiovascular enemy, it is considered a relatively reliable indicator of a person’s general health, including their brain. For a long time, excess cholesterol and other lipids in the blood have been associated with an increased risk of developing neurodegenerative pathologies, of which 60 to 80% of cases relate to Alzheimer’s disease. Nevertheless, very few studies have demonstrated the real impact of variations in the blood level of these lipids over time. In a retrospective analysis published in the journal Neurology, a team of American researchers clarified this link.
To find out if fluctuations in plasma lipid levels influence the risk of developing dementia, the scientists analyzed health data from a sample of 11,571 people aged 60 or over. Specifically, they collected measurements of triglycerides, “bad” cholesterol (LDL), “good” cholesterol (HDL) and total cholesterol from these people over five years of follow-up. They then divided the participants into five groups according to the levels of fluctuation observed: thus the two extreme groups, group 1 and group 5, correspond respectively to the 20% of participants who presented the lowest rate of variation in blood lipids and to the 20% of participants who experienced the highest rate of change. Then the researchers noted the number of participants who had developed Alzheimer’s disease or a related neurodegeneration thirteen years after the last samples were taken, which enabled them to calculate a risk. Note that at the start of the study, the participants did not suffer from any neurodegenerative disease.
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A 19% increased risk
Verdict: among all the participants, 2473 developed a neurodegenerative disease during the follow-up of the study, i.e. 21%. By comparing data from different groups of participants using statistical models, the researchers showed that those who experienced the greatest changes in their cholesterol levels (group 5) had a 19% increased risk of being one day with dementia compared to the group in which this fluctuation was the lowest (group 1). Similarly, the risk was increased by 23% for people whose triglyceride levels had varied the most during the five years of follow-up. “However, care must be taken when interpreting the results: the increased risk of developing cognitive decline is not proportional to the level of variation in the blood lipids measured”, explains Jérôme Braudeau, doctor in neurosciences, specialist in the disease. of Alzheimer’s and co-founder of the company AgenT. “The fact remains that being among individuals whose blood cholesterol and triglyceride levels fluctuate little throughout life seems to reduce the risk of cognitive decline,” he continues.
But the biggest limitation of this study is that 79% of patients in group 5 received a lipid-lowering treatment, such as statins, in order to reduce excess blood cholesterol. About 40% of Group 1 participants benefited. This therefore raises the question of whether the fluctuations in blood cholesterol and triglycerides measured are of “natural” or drug origin. “Anyway, studies of such magnitude are rare and this supports the fact that cholesterol is indeed a risk factor for dementia, underlines Jérôme Braudeau. There is also the question of whether this risk is modifiable by the use of treatment to control cholesterol or triglyceride levels.
Although the reasons for such an association as well as the nature of the mechanisms involved remain poorly understood, the study brings a new piece to the puzzle, with a strong message: “They measured variations in plasma cholesterol, therefore produced by the liver and not by the brain. This confirms that neurodegenerative diseases, such as Alzheimer’s disease, are not exclusively cerebral diseases,” says Dr. Braudeau. Thus, faced with the rise of neurodegenerative diseases in the world, it is becoming urgent to understand the consequences of these pathologies in order to develop specific blood diagnostic tests and new therapeutic approaches. This study reinforces the idea that cholesterol can be taken into consideration in the search for treatments and means of early detection, but not in isolation, and by not reducing the lines of thought in the brain.
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