Can People Deliberately Alter Their Alzheimer’s Risk?Posted on October 9, 2016 by ECR Louisville in Blog, Dementia Care
A handful of modifiable risk factors appears to explain most Alzheimer’s disease cases around the world, researchers reported.
In a meta-analysis, a composite of nine risk factors — obesity, carotid artery narrowing, low educational attainment, high levels of homocysteine, depression, high blood pressure, and frailty, as well as current smoking and type 2 diabetes in Asian patients specifically — was estimated to contribute to two-thirds of Alzheimer’s cases globally, according to Jin-Tai Yu, MD, PhD, of the University of California San Francisco, and colleagues.
Specifically, Yu and colleagues found that the population attributable risk (PAR) for each of the factors individually ranged from 0.175% to 24.5%. A model combining all nine yielded a PAR of 66%, as reported in the Journal of Neurology, Neurosurgery, & Psychiatry.
Since these risk factors are at least potentially modifiable, preventive strategies may help curb the number of new cases of Alzheimer’s disease, they concluded.
They cautioned, however, that their findings are only observational — and that the true causes of Alzheimer’s disease are still elusive. Many trials, for instance, have called into question the validity of the amyloid hypothesis. Although many have thought (and some continue to think) that beta-amyloid deposition is the primary cause of the disease’s hallmark neurodegeneration, a series of failed drug therapies targeting amyloid suggests it may not be true.
For their study, Yu and colleagues assessed 323 studies conducted from 1968 to 2014, which included some 5,000 people and 93 potential risk factors.
Overall, they found grade I evidence that four medical exposures — estrogen, statin, antihypertensives, and nonsteroidal anti-inflammatory drugs (NSAIDs) — had a protective effect against Alzheimer’s.
They also found grade I evidence that four dietary factors — folate, vitamins E and C, and coffee — had a protective effect against the disease.
There was similar good-quality evidence that high levels of homocysteine were associated with an increased risk of developing Alzheimer’s, as was depression.
Other pre-existing conditions also played a role in the risk of developing Alzheimer’s disease, Yu and colleagues found.
Frailty, carotid artery narrowing, and high or low blood pressure were associated with an increased risk of developing the disease, as was type 2 diabetes, but only in Asian patients.
On the other hand, arthritis, heart disease, metabolic syndrome, and cancer were associated with a lower risk of developing Alzheimer’s.
Finally, some factors appeared to have an impact on Alzheimer’s risk depending on when they occurred in the lifespan.
For instance, having a high or low body mass index (BMI) in mid-life and low educational attainment were associated with an increased risk of the disease — but having a high BMI later in life, doing “brain exercises,” drinking lightly to moderately, and having stress were associated with a lower risk.
Current smoking was also associated with a lower risk of developing Alzheimer’s, but only in Asian patients, they added.
Yu and colleagues couldn’t find any association between Alzheimer’s disease and occupational exposure.
The study was limited because it relied on observational data — either prospective cohort studies or retrospective case-control studies — and did not include information from randomized, controlled trials. There was also statistically significant heterogeneity found in a large proportion of the studies, they added.
Still, Yu and colleagues asserted that theirs is the “first comprehensive systematic review and meta-analysis which takes into account almost all risk factors for Alzheimer’s disease suitable to be intervened via personal, clinical, and public strategy.”
“The current meta-analysis emphasized the heterogeneity of modifiable risk factors of Alzheimer’s disease and the complexity of its etiology, and indicated that the effective interventions in diet, medications, biochemical exposures, psychological condition, pre-existing disease, and lifestyle may be promising options for preventive strategies,” they wrote. “Further good-quality cohort studies and randomized controlled trials targeting these elements are necessary.”
- Reviewed by F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner
Journal of Neurology, Neuroscience, and Psychiatry
Staff Writer, MedPage Today