▎ WuXi AppTec content team editor
The brain, the "headquarters" of the human body, directs the action of the whole body, and if there is a lesion, it will affect more than one organ. When it comes to diseases that damage the brain health of the elderly, many people will think of dementia for the first time, especially Alzheimer's disease, which accounts for 50%-70% of dementia.
Indeed, dementias such as Alzheimer's disease affect about 50 million people worldwide, accounting for 5%-8% of people in their 60s; it is also the seventh largest cause of death among the top 10 causes of death in the world in 2019.
In the eyes of many people, Alzheimer's disease and other dementias are a "geriatric disease", but with more research, scientists have found that Alzheimer's disease is likely to be a life-long disease, and many risk factors have begun to affect the occurrence and development risk of the disease at a young age.
According to a study published in Alzheimer's & Dementia, lower hdL-C ("good" cholesterol) and higher triglyceride (TG) levels in the blood as early as age 35 are associated with an increased risk of Alzheimer's disease decades later; and higher blood sugar levels at age 51-60 are also associated with an increased risk of Developing Alzheimer's disease in the future.
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Researchers from institutions such as Boston University School of Medicine (BUSM) analyzed data from the Framingham Heart Study (FHS) and included a total of 4932 participants, with an average age of 50 and 52% female.
Based on age at the time they joined the study, the researchers divided participants into 3 groups: early adulthood (35-50 years), mid-adulthood (51-60 years), and late adulthood (61-70 years).
After the study began, the researchers followed up the participants every 4 years to count and measure relevant information, including basic health information such as height and weight; lifestyle information such as smoking status, alcohol consumption, and physical activity; family history of diseases such as Alzheimer's disease, hypertension, and diabetes; health-related indicators such as high-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides, blood sugar, and blood pressure; and disease information of dementia such as Alzheimer's disease.
The researchers found that as participants aged, their triglycerides, blood sugar and systolic blood pressure levels tended to rise, while HDL cholesterol levels decreased; more people began treatment for diabetes, high blood pressure and dyslipidemia.
Participants in the early, middle, and late adult groups had an average follow-up time of 35.2 years, 25.8 years, and 18.5 years, respectively. During the follow-up period, 177, 172 and 192 participants in 3 groups developed Alzheimer's disease.
After removing other factors, the researchers found that participants' HDL cholesterol, triglycerides, blood glucose, and diastolic blood pressure levels were all associated with Alzheimer's disease risk:
Every 15 mg/dL increase in HDL cholesterol levels was associated with a 15% and 18% reduction in the risk of future Alzheimer's disease among participants in the early and middle adult groups, respectively, compared with only 11% in the late adult group.
Every 15 mg/dL increase in triglycerides was associated with a 33% and 12% increased risk of future Alzheimer's disease among participants in the early and middle adult groups, respectively, and no significant effect on participants in the late adult group.
Each 15 mg/dL increase in blood glucose was associated with a 15% increased risk of future Alzheimer's disease among participants in the mid-adult group; there was no significant effect on the other two groups.
For every 10 mmHg increase in diastolic blood pressure, a 14% increased risk of Alzheimer's disease was associated with a 14% increase in participants in the late adult group. There was no clear correlation between the other two groups of participants.
In addition, the findings found that participants with prediabetes (100 mg/dL≤ blood glucose ≤ 126 mg/dL) and diabetes (≥ 126 mg/dL) were significantly at a significantly higher risk of developing Alzheimer's disease in the future and at a younger age than participants in the early and mid-adult groups who had normal blood glucose levels (< 100 mg/dL).
The researchers analyzed that HDL cholesterol, triglycerides, blood glucose and diastolic blood pressure may have an impact on Alzheimer's risk through a variety of pathways. For example, HDL cholesterol may reduce the deposition of β-amyloid (Aβ) in blood vessels and reduce Aβ-induced inflammation, thereby reducing the risk of Alzheimer's disease.
Higher blood glucose levels may promote the formation of neurofiber tangles in the brain by deposits of tau proteins, which in turn increases the risk of Alzheimer's disease. However, the researchers pointed out that the relevant mechanism is not yet clear, and more research is needed to explore.
Since this study is observational, it only shows that HDL cholesterol and triglycerides are associated with Alzheimer's disease risk, and do not indicate a causal relationship. And the study also has some limitations, such as some data relying on participants' recalls, which may also have an impact on the results.
The study concludes by highlighting that this study shows that risk factors for cardiovascular metabolism, including diabetes, obesity, high blood pressure, and elevated serum cholesterol levels, are associated with cognitive decline. Moreover, the correlation is earlier than one might think. This also adds evidence that people should protect their brain health and reduce the risk of dementia through lifestyle interventions as early as possible.
One of the study authors, Dr. Lindsay A. Farrer of Boston University School of Medicine, noted: "Intervention management of cholesterol, blood sugar, etc. from early adulthood will help maximize brain cognitive health in later life and reduce the risk of future Alzheimer's disease." ”