Age is currently the strongest known risk factor for Alzheimer’s disease, write the authors of an article appearing in the September issue of the Archives of Neurology. The only other known risk factor associated with developing the disease is variation in the apolipoprotein E gene. Existing research to ascertain other risk factors, such as diet and exercise, has been less conclusive. 

Many people were dismayed by an independent panel report issued at the State-of-the-Science Conference panel convened by the National Institutes of Health in April 2010 that current research cannot support the association of any modifying behavior with a reduced risk of cognitive decline or Alzheimer’s disease.

Panelists evaluated existing English-language research from 1984 through 2009 and weighed the level of evidence for each risk factor (low, moderate or high) and rated studies accordingly (low for observational studies vs. high for randomized controlled trials).

The Archives of Neurology article addresses, in part, the many concerns generated by that report. It found methodological limitations in many of the studies that make firm conclusions impossible. “Large-scale, long-term, population-based studies and clinical trials are urgently needed to identify risk factors for Alzheimer’s disease,” write the authors, suggesting using studies similar to the Framingham Heart Study, a large and long-running study that helped reveal common factors contributing to major cardiovascular diseases.

The most common form of dementia, Alzheimer’s affects as many as 5.3 million Americans, a number likely to increase as baby boomers grow older. Yet we know little about a disease whose costs in the United States are estimated at $183 billion, a number expected to rise to $1.1 trillion by 2050. Finding a way to delay its onset, whether with modified behaviors or medications, could have dramatic effects by cutting the number of cases in half and saving nearly $450 million a year by 2050, says the Alzheimer’s Association.

While current evidence does not support the association of any modifiable factor for reducing the risk of cognitive decline, the panelists write that they hope their report “will instigate rigorous high-quality research that can provide conclusive evidence on this issue.” Until more conclusive results become available, they counsel, “individuals should continue to aim for a physically and mentally active and healthy lifestyle” and pay special attention to “well-known major risk factors for chronic diseases.”