Effect of Exercise and Diet on Alzheimer’s

A review of an important, recently published scientific article selected by The North American Menopause Society (NAMS) and published in their newsletter.

 

Scarmeas N, Luchsinger JA, Schupf N, et al. Physical activity, diet, and risk of Alzheimer disease. JAMA 2009;302:627-637. Level of evidence: II-2. ,

Abstract copyright © American Medical Association. All rights reserved. Used with permission.

 

CONTEXT: Both higher adherence to a Mediterranean-type diet and more physical activity have been independently associated with lower Alzheimer disease (AD) risk but their combined association has not been investigated.

OBJECTIVE: To investigate the combined association of diet and physical activity with AD risk.

DESIGN, SETTING, AND PATIENTS: Prospective cohort study of 2 cohorts comprising 1880 community-dwelling elders without dementia living in New York, New York, with both diet and physical activity information available. Standardized neurological and neuropsychological measures were administered approximately every 1.5 years from 1992 through 2006. Adherence to a Mediterranean-type diet (scale of 0-9; trichotomized into low, middle, or high; and dichotomized into low or high) and physical activity (sum of weekly participation in various physical activities, weighted by the type of physical activity [light, moderate, vigorous]; trichotomized into no physical activity, some, or much; and dichotomized into low or high), separately and combined, were the main predictors in Cox models. Models were adjusted for cohort, age, sex, ethnicity, education, apolipoprotein E genotype, caloric intake, body mass index, smoking status, depression, leisure activities, a comorbidity index, and baseline Clinical Dementia Rating score.

MAIN OUTCOME MEASURE: Time to incident AD.

RESULTS: A total of 282 incident AD cases occurred during a mean (SD) of 5.4 (3.3) years of follow-up. When considered simultaneously, both Mediterranean-type diet adherence (compared with low diet score, hazard ratio [HR] for middle diet score was 0.98 [95% confidence interval {CI}, 0.72-1.33]; the HR for high diet score was 0.60 [95% CI, 0.42-0.87]; P = .008 for trend) and physical activity (compared with no physical activity, the HR for some physical activity was 0.75 [95% CI, 0.54-1.04]; the HR for much physical activity was 0.67 [95% CI, 0.47-0.95]; P = .03 for trend) were associated with lower AD risk. Compared with individuals neither adhering to the diet nor participating in physical activity (low diet score and no physical activity; absolute AD risk of 19%), those both adhering to the diet and participating in physical activity (high diet score and high physical activity) had a lower risk of AD (absolute risk, 12%; HR, 0.65 [95% CI, 0.44-0.96]; P = .03 for trend).

CONCLUSION: In this study, both higher Mediterranean-type diet adherence and higher physical activity were independently associated with reduced risk for AD.

 

Comment.

Previous studies referenced by the author have shown a Mediterranean-type diet to be associated with lower risk for AD and mild cognitive impairment; and higher rates of physical activity have been associated with lower rates of cognitive decline and dementia. It is therefore not surprising that the authors concluded that both a Mediterranean-type diet and physical activity were independently associated with reduced risk of AD, though magnitude of benefit did not increase with both. Limitations of this study include the bias that individuals who are able to adhere to these healthy behaviors are in better mental health at baseline and therefore less likely to develop AD.

Furthermore, these healthier individuals may be more likely to remain in the study cohort, evidenced by the characteristics of those lost to follow up: less educated, higher caloric intake, higher body mass index, and more comorbidities. While the authors took steps to control for these factors, such bias is inherent in observational studies of this type and cannot be completely controlled. The question is whether this bias negates the results of this study and many others that tout the benefits of the Mediterranean-type diet and higher levels of physical activity.

The Mediterranean-type diet has been associated with many health benefits, most notably the reduction of cardiovascular disease (CVD). The Lyon Diet Heart Study showed a 50% to 70% reduction in coronary heart disease (CHD) recurrence including fatal and nonfatal myocardial infarction (MI) and stroke in those adhering to the Mediterranean diet.1 Similarly, increased physical activity has been associated with many health benefits including but not limited to reduced relative risk of CHD by almost 20%, as demonstrated by the Harvard Alumni Health Study.2 The effect of Mediterranean-type diet and physical activity on CVD are not insignificant given that CVD remains the number one cause of death in the United States. Certainly, these findings are relevant to patients with AD as they are typically advanced in age and are demographically the same patient population afflicted by CVD. Furthermore, CVD (specifically cerebrovascular disease) could significantly impact the clinical expression and degree of cognitive compromise suffered by patients with AD.3 Given these findings, it seems prudent to endorse a Mediterranean-type diet and physical activity as a means to mitigate cognitive decline in AD patients, as well as reduce concomitant disease burden.

 

Adrienne Youdim, MD
Director, Medical Weight Loss
Cedars-Sinai Center for Weight Loss
Assistant Clinical Professor
UCLA School of Medicine
Los Angeles, CA

 

References:

  1. Michel L, Salen P, Martin JL, Monjaud I, Delaye J, Mamelle N. Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation 1999;99:779-785.
  2. Sesso HD, Paffenbarger RS, Lee M. Physical activity and coronary heart disease in men: the Harvard Alumni Health Study. Circulation 2000;102:975-980.
  3. Knopman, DS. Mediterranean diet and late-life cognitive impairment: a taste of benefit. JAMA 2009;302:686-687.
 
 
Author
Dr. Adrienne Youdim

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