Modifiable Risk Factors Could Explain 66% of AD Cases
Nine risk factors—hypertension, obesity, depression, type 2 diabetes, frailty, current smoking, low educational achievement, hyperhomocysteine, and carotid artery narrowing—could account for two-thirds of Alzheimer’s disease (AD) cases worldwide, according to a recent meta-analysis.
“The aetiology of Alzheimer's disease (AD) is believed to involve environmental exposure and genetic susceptibility. The aim of our present systematic review and meta-analysis was to roundly evaluate the association between AD and its modifiable risk factors,” researchers wrote.
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For the study, researchers examined data from 16,906 articles and identified 323 containing 93 risk factors that met their inclusion criteria.
First, researchers identified several modifiable factors that could protect against AD.
“Among factors with relatively strong evidence (pooled population >5000) in our meta-analysis, we found grade I evidence for 4 medical exposures (oestrogen, statin, antihypertensive medications and non-steroidal anti-inflammatory drugs therapy) as well as 4 dietary exposures (folate, vitamin E/C and coffee) as protective factors of AD,” explained the study’s authors.
Conversely, researchers discovered a significant increased risk of developing AD associated with depression and exposure to the amino acid homocysteine.
They also found grade 1 evidence indicating the “complex roles” that pre-existing conditions—specifically frailty, carotid atherosclerosis, hypertension, low diastolic blood pressure, type 2 diabetes mellitus—play in increasing the risk of AD.
Further, they found that a history of arthritis, heart disease, metabolic syndrome, and cancer, as well as lifestyle factors—including low education, high BMI, current smoking, moderate drinking, stress—can also influence the risk of developing AD.
Overall, the population attributable risk (PAR) for each of the factors ranged from 0.175% to 24.5%. A statistical model combining all 9 factors yielded a PAR of 66%.
“Effective interventions in diet, medications, biochemical exposures, psychological condition, pre-existing disease and lifestyle may decrease new incidence of AD,” they concluded.
The complete study is published in the August issue of the Journal of Neurology, Neurosurgery and Psychiatry.
-Michelle Canales
Reference:
Xu W, Tan L, Wang HF, et al. Meta-analysis of modifiable risk factors for Alzheimer’s disease. J Neurol Neurosurg Psychiatry. 2014 August [epub ahead of print] doi: 10.1136/jnnp-2015-310548.