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More on Exercise, Diet Lower Alzheimer's Risk
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More on Exercise, Diet Lower Alzheimer's Risk
Exercise, Diet Lower Alzheimer's Risk
New York (Mar 23, 2010)
Alzheimer's disease is a devastating illness that by degrees robs people of their memories, their independence, their connections to those closest to them, and eventually their lives. Almost 5.3 million Americans now have Alzheimer's, and that number is projected to quadruple over the next 50 years as the number of older Americans expands. A growing body of evidence, including a new study by NewYork-Presbyterian neurologist Nikolaos Scarmeas, suggests that lifestyle changes already recommended for cardiovascular health can help prevent Alzheimer's disease. Dr. Scarmeas's study in JAMA (vol 302; no. 6; p. 627-637) underscores the link between a healthy (Mediterranean-type) diet, exercise, and a reduced risk of developing Alzheimer's.
Dr. Scarmeas and colleagues in NewYork-Presbyterian/Columbia University Medical Center's Department of Neurology tracked the health of 1,800 subjects in a multi-ethnic community aged 65 or older in northern Manhattan over approximately 5.5 years. About half of the subjects were Hispanic; the rest were equally African-American or white. The researchers met with the subjects approximately every year and a half in their homes, recording their dietary habits and physical activity, and assessing their mental status with standardized neurological and neuropsychological measures. Over the course of the study 282 of the 1,800 subjects developed Alzheimer's disease.
Dr. Nikolaos Scarmeas
We found that those people who were following a healthier diet (high levels of fruits, vegetables, legumes, cereals, and fish, and low levels of meat and dairy products) had a lower risk for getting Alzheimer's disease, and similarly those people who were more physically active had a lower risk for getting Alzheimer's disease," said Dr. Scarmeas. People who followed a very healthy diet and were also most physically active had a 9% chance of developing Alzheimer's while those who did neither had a 21% chance of developing the disease. The researchers initially set out to determine if a healthy diet and exercise together have additive benefits. "You had independent protection from both activities, but there was no dynamic synergy," said Dr. Scarmeas.
"This study did a very good job of addressing potential methodologic shortcomings of epidemiologic investigations and it found evidence supporting both physical exercise and the Mediterranean diet as potentially risk-lowering for Alzheimer's disease," said neurologist Norman Relkin, Director of the Memory Disorders Program at NewYork-Presbyterian/Weill Cornell Medical Center. "It is consistent with other studies suggesting that diet and exercise modification may help prevent dementia," he added.
Several biological mechanisms may be at work, said Dr. Scarmeas. "There is evidence that a Mediterranean-type diet and physical activity are associated with a low risk for hypertension, dyslipidemia, diabetes, heart disease, obesity – and more and more studies are showing that these cardiovascular risk factors may be related to increased risk for Alzheimer's disease," he said. "We also know that physical activity and a healthy diet are associated with lower inflammation and oxidative stress, both biological mechanisms implicated in Alzheimer's disease pathogenesis."
Dr. Norman R. Relkin
"There is a general hypothesis that the Alzheimer brain is more subject to damage from a variety of causes. Anything that you can do to mitigate that damage is going to be beneficial, either in preventing or delaying onset. Interventions that are heart-healthy and promote the health of the vascular system are also going to preserve the health of the brain," Dr. Relkin said. "Diets loaded with carbohydrates or saturated fats may promote amyloid-related changes in the brain."
Lifestyle changes even after a diagnosis of Alzheimer's may affect the course of the disease. In an earlier study (Scarmeas et al. Neurology 2007; 69: 1084-1093) Dr. Scarmeas and colleagues found that "a higher adherence to a healthy diet even after you develop Alzheimer's disease was associated with reduced mortality," Dr. Scarmeas said. "In other words, people with Alzheimer's disease who followed a healthy diet lived longer."
Dr. Relkin consults with relatives of patients with Alzheimer's and others who are at high risk for one reason or another. Beyond assessing and treating hypertension, a known Alzheimer's risk factor, "lifestyle modification is currently the only advice we can give them to lower their dementia risk," he said. "What's heart-healthy is also good for the brain," he tells this group.
Dr. Scarmeas is currently planning additional studies to investigate the mechanism and effects of diet and exercise on Alzheimer's risk. Interventional studies of Alzheimer's disease are difficult to implement, he said. "One of the main limitations in the Alzheimer's disease field is that we lack both a diagnostic biomarker or a biomarker as an outcome for this disease."
"The JAMA study presents very encouraging evidence that Alzheimer's disease is the result of both genetic influences and 'lifetime exposures,'" said Dr. Relkin. "Dr. Scarmeas and colleagues have focused on an area that is still very understudied. There is a pressing need to know the value of these interventions in reducing dementia risk so that we are able to design effective public health initiatives."
Nikolaos Scarmeas, M.D., is an Assistant Attending Neurologist at the Taub Institute for Research on Alzheimer's Disease and the Aging Brain at NewYork-Presbyterian Hospital/Columbia University Medical Center and an Assistant Professor in Clinical Neurology at Columbia University College of Physicians and Surgeons.
Norman R. Relkin. M.D., Ph.D., is the Director of the Alzheimer's Disease & Memory Disorders Program and an Associate Attending Neurologist at NewYork-Presbyterian Hospital/Weill Cornell Medical Center. He is also an Associate Professor of Clinical Neurology and Neuroscience at Weill Cornell Medical College.