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High cholesterol levels in middle age are associated with an increased risk of developing dementia and Alzheimer’s disease more than a decade later, according to new research.
High levels of low density lipoprotein (LDL) were linked to an increased risk of developing the conditions.
While high levels of total cholesterol were also associated with increased risk, this link was weaker, suggesting that it is largely due to LDL cholesterol, according to the researchers.
The study provides the strongest evidence to date on the relationship between blood cholesterol and dementia and Alzheimer’s disease. It was led by the London School of Hygiene & Tropical Medicine (LSHTM) with the University of Tsukuba, Japan and OXON Epidemiology, London and Madrid.
Head of the study, Dr Nawab Qizilbash is a Senior Clinical Epidemiologist at OXON Epidemiology and Honorary Associate Professor of Pharmacoepidemiology at LSHTM.
He said: “Although the link between LDL cholesterol and dementia and Alzheimer’s disease is modest and found in people followed from middle age for more than 10 years, any modifiable risk factor is the welcome to this huge, emerging and devastating disease.
“Most of the known risk factors are difficult to change, and convincing evidence that changing them can prevent dementia or Alzheimer’s disease is scarce.
Likewise, a long-term follow-up (more than 10 years) of randomized and non-randomized studies is needed to assess whether the benefits of LDL cholesterol-lowering interventions – which significantly reduce coronary heart disease – can further reduce the risk. of dementia or Alzheimer’s disease. ”
Funded by Alzheimer’s UK, the researchers used anonymized data from the UK Clinical Practice Research Database (CPRD) on more than 1.8 million UK adults.
They were all over 40 years old and had their blood cholesterol measured between 1992 and 2009, with a follow-up period of up to 23 years or until the diagnosis of dementia.
In what is considered the largest study of its kind, researchers were able to calculate the risks of subsequent dementia and Alzheimer’s disease for blood total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides, by adjusting other factors.
The researchers focused on measuring blood cholesterol taken at middle ages (under 65) who have less disease.
A follow-up period of more than 10 years meant that they could avoid bias resulting from a long period of silence when pathology was present but symptoms were clinically absent or vague.
Of the 953,635 people in the study who recorded LDL cholesterol, 2.3% (21,602) were diagnosed with dementia or Alzheimer’s disease.
Of the more than 1.8 million people who had their first total cholesterol reading, almost 50,000 (2.7%) were subsequently diagnosed during the 23-year follow-up period, up to 2015 .
The study found that the associations were weaker in people whose blood cholesterol levels were measured after the age of 65.
No consistent association was observed for cholesterol or high density lipoprotein (HDL) triglycerides.
Lead author Dr Masao Iwagami, Assistant Professor at the University of Tsukuba and Honorary Associate Professor of Epidemiology and Population Health at LSHTM, said: “Our study surpasses all previous studies in size and provides very precise results. .
“In people whose cholesterol was measured before the age of 65, the risk of dementia diagnosed more than 10 years later was about 60% higher in those with LDL cholesterol above 200 mg / dL (5.17 mmol / L) compared to those whose level was less than 100%. mg / dL (2.6 mmol / L).
“The strength of this association is comparable to other modifiable risk factors such as alcohol consumption and greater than that of blood pressure.”
The authors recognize the limitations of the study, including the lack of information on diet or physical activity, so it was not possible to assess the influence of these factors on blood cholesterol. and how this might affect the associations observed.
The study is published in Lancet Healthy Longevity.
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