Modifiable Risk Factors and Cognition:
New Evidence that Lifestyle Choices can Reduce the Risk of Cognitive Decline and Alzheimer’s Disease

Renehan-300pxWilliam E. Renehan, Ph.D.
Associate Director, George and Anne Ryan Institute for Neuroscience

Those of us with a strong family history of late-onset (sporadic) Alzheimer’s disease (AD) are confronted with a disheartening predicament – we justifiably fear that we have an increased risk for developing AD, but there are currently no medications that we can employ to prevent, or even delay, the onset of the disease. A family history of AD is one of the greatest risk factors for developing late-onset AD, together with age and the presence of one or more of the genetic susceptibility genes (approximately 22 have been identified thus far). Needless to say, there is nothing we can do to change our family disease history or genetic makeup or stop the process of aging. These risk factors are thus non-modifiable. There are, however, a number of potential AD risk factors that are modifiable. These include cardiovascular risk factors such as diabetes, obesity and hypertension and lifestyle risk factors such as physical activity, diet, alcohol intake, smoking, cognitive training and social engagement.

A recent report by Dr. Matthew Baumgart and colleagues at the Alzheimer’s Association concludes that there is now sufficient evidence to support a link between several modifiable risk factors and cognitive decline [1]. This team evaluated the scientific literature and determined that there was good reason to believe that regular physical activity and management of cardiovascular risk factors can reduce the risk of cognitive decline and may even reduce the risk of dementia. They also concluded that there was evidence that a healthy diet and lifelong learning/cognitive training may reduce the risk of cognitive decline. Additional support for the value of pursuing strategies that address modifiable risk factors was published in a subsequent issue of the same journal [2]. Investigators at the University of Pittsburgh followed 800 cognitively normal older adults for three years and found that moderate physical exercise, particularly when combined with cognitively demanding activities such as taking a course, decreased the risk of developing Mild Cognitive Impairment (MCI) (cognitive decline that includes problems with memory, language and judgement but does not interfere with daily functioning or independent function).

There is some evidence that the intensity of the physical activity is important in preventing or reversing cognitive decline. A paper published in the Journal of Alzheimer’s Disease in early September of this year describes the results that were obtained when a group of investigators in Helsinki, Finland examined the association between midlife physical activity and cognition in old age [3]. The investigators followed participants in the Finnish Twin Cohort for 25 years and found that individuals that engaged in the most strenuous activity (e.g. running vs. walking or jogging) had a decreased risk for subsequent impaired cognition.

Laura Baker, Ph.D., Associate Professor of Gerontology and Geriatric Medicine at Wake Forest Baptist Medical Center, has also demonstrated the importance of engaging in strenuous exercise. Paula Grammas, PhD, Executive Director and I were fortunate to be able to attend Dr. Baker’s plenary presentation at the 2016 Alzheimer’s Association International Conference in Toronto where we heard the results of a prospective study of 70 older adults with MCI. Baker and colleagues found that participants that engaged in 45 minutes of high-intensity aerobic exercise (heart rate at 70-80% of maximum rate) four times per week for six months exhibited marked improvement in their executive function (attention, planning and organizing abilities). The participants that engaged in mild physical activity (heart rate at or below 35% of maximum) showed no improvement. What distinguishes this study from the others I have discussed is that this investigation looked at more than the ability of exercise to reduce the risk of developing MCI – it provided evidence that exercise can actually reverse deficits in executive function in MCI patients. This is an outcome that has thus far eluded the many drug trials that have been conducted in dementia patients and is remarkable in that the intervention is accompanied by virtually no risks or side effects (assuming the patients are medically fit to engage in vigorous exercise).

In addition to physical exercise and cognitive activity, there is growing support for the value of an additional lifestyle modification that may significant value in preventing cognitive decline – diet. A number of studies have provided evidence that the consumption of a “Mediterranean diet” (a diet high in vegetables, fruits, legumes and fish with moderate alcohol intake) may reduce the risk of cognitive decline and AD and a very recent study by investigators at the Mayo Clinic has shown that this diet actually increases the thickness of the cerebral cortex [4].

Two other recent studies led by Martha Morris at Rush University Medical Center in Chicago provide evidence that a specific type of Mediterranean diet is particularly effective [5, 6]. Morris and colleagues developed a Mediterranean-type diet that they call the MIND diet that is particularly rich in green leafy vegetables (two servings per day) and berries (two servings per week) but does not emphasize the consumption of other types of fruits, dairy products or more than one serving of fish per week. The team found that greater adherence to the consumption of the MIND diet was associated with a slower decline in cognitive skills and in fact was equivalent to being 7.5 years younger in cognitive tests. Greater adherence to the diet reduced the chance of developing AD by as much as 53%, an effect much greater than that associated with the standard Mediterranean diet.

There is now compelling evidence that some specific lifestyle modifications have the very real ability to reduce the rate of age-related cognitive decline and the risk of developing AD. Moreover, in the case of physical activity, there is reason to believe that vigorous activity may actually improve cognition in patients that have developed MCI. Those of us at increased risk of developing AD have some concrete steps we can take to preserve our cognition. In my case, where one parent and two of this parent’s siblings died of AD, I consider it imperative that I increase my activity to include four 45-minute aerobic exercise sessions per week (heart rate at 70-80% of maximum), commit to the MIND diet and continue to challenge myself intellectually.

The George and Anne Ryan Institute for Neuroscience is actively developing collaborations and affiliations with community partners to communicate the importance of these lifestyle choices and to help our friends, neighbors and co-workers achieve their lifestyle goals. We look forward to working with you in these outreach efforts and welcome your suggestions in this and all our endeavors.

References

  1. Baumgart, M., et al., Summary of the evidence on modifiable risk factors for cognitive decline and dementia: A population-based perspective. Alzheimers Dement, 2015. 11(6): p. 718-26.
  2. Hughes, T.F., et al., Independent and combined effects of cognitive and physical activity on incident MCI. Alzheimers Dement, 2015. 11(11): p. 1377-84.
  3. Iso-Markku, P., et al., Midlife Physical Activity and Cognition Later in Life: A Prospective Twin Study. J Alzheimers Dis, 2016.
  4. Staubo, S.C., et al., Mediterranean diet, micronutrients and macronutrients, and MRI measures of cortical thickness. Alzheimers Dement, 2016.
  5. Morris, M.C., et al., MIND diet associated with reduced incidence of Alzheimer’s disease. Alzheimers Dement, 2015.
  6. <Morris, M.C., et al., MIND diet slows cognitive decline with aging. Alzheimers Dement, 2015. 11(9): p. 1015-22.