PARIS – A 25% reduction in seven potentially modifiable lifestyle-based risk factors for Alzheimer’s disease could lower the prevalence of Alzheimer’s cases by 3 million worldwide, according to the findings of a study presented July 19 at the International Conference on Alzheimer’s Disease.
Just a 10% reduction in the factors could lower the prevalence of cases by 1 million, Deborah Barnes, Ph.D., reported at the conference, sponsored by the Alzheimer’s Association.
She and her colleagues calculated population attributable risks using data from recent systematic reviews and meta-analyses, and found that worldwide, low educational attainment was associated with the highest proportion (19%) of potentially attributable cases of Alzheimer’s disease, followed by smoking (14%), physical inactivity (13%), depression (11%), midlife hypertension (5%), midlife obesity (2%), and diabetes (2%).
Among subjects in the United States, where the prevalence of some risk factors such as educational attainment differ from the worldwide prevalence, thus affecting the population attributable risks, physical inactivity had the highest associated proportion of potentially attributable cases of Alzheimer’s disease (21%), followed by depression (15%), smoking (11%), midlife hypertension (8%), midlife obesity (7%), low educational attainment (7%), and diabetes (3%).The findings were published simultaneously in the Lancet Neurology (Lancet Neurol. 2011 July 19 [doi:10.1016/S1474-4422(11)70072-2]).
The mathematical modeling used by Dr. Barnes and her colleagues for this study indicates that when combined, these seven risk factors contribute to more than half of the nearly 36 million cases of Alzheimer’s disease worldwide and nearly 60% of the 6 million cases in the United States. The investigators selected the seven factors because they have the most consistent evidence for an association with Alzheimer’s disease, Dr. Barnes said during a press briefing.
This is particularly important given that the prevalence of Alzheimer’s disease is expected to almost triple to 106 million by 2050. The current absence of effective disease-modifying treatment, and an increasing awareness that symptoms develop over many years, has contributed to the interest in identifying effective prevention strategies, said Dr. Barnes of the department of psychiatry at the University of California, San Francisco.
"There are no cures or treatments that modify the course of disease right now, so we’re really focusing on identifying strategies for prevention," she said.
Many potentially modifiable risk factors have been identified, but it remains unclear which factors should be targeted. Therefore, Dr. Barnes and her associates set out to estimate what the impact of risk factor reduction strategies would be on Alzheimer’s disease prevalence.
She cautioned that their findings were derived by making an important, but unproven, assumption that a causal relationship exists between the risk factors and Alzheimer’s disease, and that modifying the risk factors will lower the risk of developing Alzheimer’s disease.
But the factors are promising nonetheless, she said. "I think the findings are exciting, because they suggest that public health interventions to increase education and physical activity and reduce smoking rates and depression could potentially have a really dramatic impact on Alzheimer’s disease prevalence over time, so I feel like it gives us a little bit of hope about things we might be able to do now to try to prevent the epidemic we see coming our way," she said.
The next step is to conduct randomized controlled intervention trials to test the impact of prevention strategies, she said, also adding that campaigns to promote risk factor modification among the public should be considered.
Dr. Ronald Petersen, who moderated the press briefing, agreed the findings provide hope in the fight against Alzheimer’s disease.
A theme that has been emerging, and which is underscored by these findings is that "the development of cognitive impairment, and Alzheimer’s disease in particular, need not be a passive process," said Dr. Petersen, professor of neurology and director of the Alzheimer’s Disease Research Center at the Mayo Medical School, Rochester, Minn.
"I think what we’re realizing is that we can do something about this. We may not be able to prevent [Alzheimer’s disease], or stop it in its tracks by lifestyle modification, but I think there are significant inroads that can be made into this disease," he said.
Dr. Barnes had no relevant disclosures. Dr. Petersen disclosed that he chairs data safety monitoring committees for Pfizer and Janssen Alzheimer Immunotherapy, and serves as a consultant for Elan and GE Healthcare.