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• Time of issue:2022-03-21 15:38
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(Summary description)Dementia affects an estimated 50 million people worldwide, and this number is expected to more than triple by 2050, especially in low- and middle-income countries, where, according to the report, about two-thirds of people with dementia live. Women are also more likely to develop dementia than men.

 



There is currently no cure for this form of dementia, so prevention is especially important in reducing the growing global burden of dementia. According to the Lancet Commission on Dementia Prevention, Intervention and Care, 40% of dementia cases can be attributed to modifiable risk factors, including lower education levels, high blood pressure, obesity, hearing loss, smoking, depression , physical inactivity, social isolation, diabetes, alcohol consumption, traumatic brain injury and air pollution.

 



 


Notably, dyslipidemia was not included in the list of modifiable risk factors. So in preventing dementia, is there no need to worry about cholesterol?

High levels of low-density lipoprotein cholesterol (LDL-C) in midlife are associated with an increased risk of dementia ten years later, according to a recent study published in the journal Lancet Health and Longevity. The study found that among people under the age of 65 whose cholesterol was measured, those with LDL-C levels above 190 mg/dL (4.92 mmol/L) had more LDL-C levels over 10 years than those with levels below 100 mg/dL (2.59 mmol/L). The risk of later being diagnosed with dementia was about 60% higher.

The strength of the association between LDL-C and dementia was comparable to that of alcohol consumption and even greater than that of hypertension risk factors. The study provides the strongest evidence yet on the relationship between blood cholesterol and dementia and Alzheimer's disease.


 



DOI:10.1016/S2666-7568(21)00150-1

 


Low-density lipoprotein is a lipoprotein particle that carries cholesterol into peripheral tissue cells. Since cholesterol must be combined with lipoproteins to be transported to various parts of the body, cholesterol often exists in the form of lipoproteins in the blood, mainly divided into low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) . Low-density lipoprotein transports cholesterol from the liver to tissues throughout the body, and high-density lipoprotein transports cholesterol from various tissues back to the liver for metabolism.

When there is an excess of low-density lipoprotein, the cholesterol it carries will accumulate on the arterial wall, which can easily cause arteriosclerosis for a long time. Therefore LDL is called "bad cholesterol".

So what level of "bad cholesterol" LDL-C represents dyslipidemia? In order to let the public have a good understanding of their blood lipid health, the NCEP ATP III report in the United States divides LDL-C into 5 levels for the prevention and treatment of dyslipidemia, as follows:


 

 


< 2.59 mmol (100 mg/dL) is an appropriate level;
2.59 ~ 3.34 mmoL (100 ~ 129 mg/dL) is a near appropriate level;
3.38 ~ 4.12 mmol/L (130 ~ 159 mg/dL) is a critical high level;
4.14 ~ 4.89 mmol/L (160 ~ 189 mg/dL) is high;
≥ 4.92 mmol/L (190 mg/d) is an extremely high level


 


For the study, researchers took blood cholesterol measurements of more than 1.8 million British adults over the age of 40 between 1992 and 2009 and followed them for up to 23 years. The investigators stratified analyses according to age at first measurement (<65 years or ≥65 years) and duration of follow-up (<10 years or ≥10 years).

Because of the large cohort size, the researchers focused on blood cholesterol measurements in middle-aged (under 65 years old) with less disease and followed up for more than 10 years. The researchers analyzed blood total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides with subsequent risk of dementia and Alzheimer's disease.

At the end of study follow-up, among those diagnosed with dementia, the mean age at diagnosis was 79.7 years for men and 82.1 years for women. The average level of blood lipids was 5.62mmol/L (total cholesterol), the average level of low-density lipoprotein was 3.42mmol/L; the average level of high-density lipoprotein cholesterol was 1.45mmol/L.

Findings found a modest positive association between LDL cholesterol and dementia, with an adjusted ratio (RR) for each SD increase in LDL cholesterol (1.01 mmol/L or 39 mg/dL increase) of 1.05. This suggests that higher LDL cholesterol levels are associated with greater risk of dementia.

Is there a difference between lipid levels in middle age and later life and dementia risk?


To clarify this question, the researchers further analyzed that, for people younger than 65 years (middle age) when their cholesterol was first measured and diagnosed with dementia 10 years after their cholesterol was measured, each 1-1 increase in LDL cholesterol The adjusted RR for one SD was 1.17; for those diagnosed with Alzheimer's disease, the adjusted ratio (R