Nine potentially modifiable risk factors may contribute to up to two thirds of Alzheimer’s disease cases worldwide, analysis has suggested.
US and Chinese researchers suggested preventive strategies, targeting diet, drugs, body chemistry, mental health, pre-existing disease, and lifestyle may help to prevent Alzheimer’s.
The study authors looked at a range of factors previously linked with Alzheimer’s disease in order to try and determine the degree that they might be modified and, therefore, potentially reduce the risk.
“Effective interventions in diet, medications, biochemical exposures, psychological condition, pre-existing disease and lifestyle may decrease new incidence of Alzheimer’s disease”
The researchers looked at 323 studies covering 93 different potential risk factors and more than 5,000 people.
The evidence indicated a strong association between a significantly heightened risk of developing Alzheimer’s disease and high levels of the amino acid homocysteine and depression.
It also strongly pointed to the complex roles of pre-existing conditions as either heightening or lowering the risk.
The factors associated with a heightened risk included frailty, carotid artery narrowing, high and low blood pressure, and type 2 diabetes – among Asian patients.
Certain factors seemed to be linked to altered risk, depending on the time of life and ethnic background.
For example, high or low body mass index in mid-life and low educational attainment were associated with increased risk. But high BMI in later life, exercising the brain, smoking, light to moderate drinking and stress were associated with lowered risk.
The researchers then looked for nine risk factors that had strong evidence in favour of an association with Alzheimer’s disease in the pooled analysis.
The nine risk factors included obesity, carotid artery narrowing, low educational attainment, high levels of homocysteine, depression, hypertension and frailty – and in the Asian population – current smoking and type 2 diabetes.
Mathematical formulas indicated that these nine factors, each of which is potentially modifiable, contribute up to around two thirds of cases globally, said the authors published online in the Journal of Neurology Neurosurgery & Psychiatry.
In contrast, they found strong evidence for a protective effect from taking statins, hypertension drugs, oestrogen and non-steroidal anti-inflammatory drugs. They also found the same level of evidence for folate, vitamins C and E and coffee.
The researchers suggested preventive strategies targeting diet, prescription drugs, body chemistry, mental health, underlying disease and lifestyle might help curb the number of new Alzheimer’s cases.
Factors found to increase Alzheimer’s risk:
- Carotid artery narrowing
- Low educational attainment
- High levels of homocysteine
- Current smoking (in the Asian population)
- Type 2 diabetes (in the Asian population)
Factors found to have protective affect:
- Hypertension drugs
- Non-steroidal anti-inflammatory drugs
- Vitamin C
- Vitmain E