Results from a recent study published in the Journal of Neurology Neurosurgery & Psychiatry revealed nine possibly modifiable risk factors that may contribute towards up to two thirds of all cases of Alzheimer’s disease (AD) worldwide. However, the results also suggest that AD is a complex condition with many risk factors accounting for its development.
In the study, a team of researchers indicates that preventive strategies for AD such as those that target drugs, diet, body chemistry, pre-existing disease, mental health, and lifestyle may help people to stave off dementia. These strategies are particularly relevant as there is no cure for dementia.
In the study, the team examined risk factors associated with the development of AD and assessed the degree to which these risk factors could be modified in order to reduce overall risk for the condition.
Scientists analyzed studies published between 1968 and 2014 and found 323 studies that covered 93 risk factors comprising more than 5000 people. In a pooled analysis, each study was graded based on its strength. The results revealed grade 1 level evidence in favor of a protective effect for cholesterol lowering drugs (statins), anti-inflammatory drugs (NSAIDs), female hormone oestrogen and drugs to lower high blood pressure. The results also showed there is the same degree of evidence for the protective effect of vitamins C and E, coffee and folate.
High levels of homocysteine – an amino acid manufactured in the body – were strongly associated with depression and an increased risk for AD. Pre-existing conditions were also associated with either a lowered or heightened risk.
Specifically, the risk factors found to be associated with an increased risk for AD were carotid artery narrowing, type 2 diabetes (in the Asian population), frailty, high and low blood pressure, while risk factors associated with a decreased risk in AD development included a history of heart disease, metabolic syndrome, arthritis, and cancer.
The results also revealed that low or high body mass index (BMI) in mid-life and low educational achievement were related with a heightened risk for AD, while a high BMI in later life, current smoking (excluding the Asian population), light to moderate drinking, exercising one’s brain, and stress were all factors associated with a lower risk for AD.
The team also examined the population attributable risk (PAR) for nine different risk factors for AD development, including current smoking (in the Asian population), carotid artery narrowing, obesity, low educational attainment, type 2 diabetes (in the Asian population), depression, high blood pressure, frailty, and high levels of homocysteine. All these factors had been found to have a great impact in the development of the disease. PAR is used to determine the proportion of a condition in a specific population that would disappear if exposure to a specific risk factor were to be eradicated. The study demonstrated that each of these risk factors contributed up to around two thirds of all cases of AD worldwide.
Although no definite conclusions can be drawn from the results of this study, they do indicate that preventive strategies, targeting diet, prescription drugs, body chemistry, mental health, underlying disease, and lifestyle might help to reduce the incidence of Alzheimer’s disease.