Physical Activity May Not be a Key in the Mysteries of Dementia

Caitlin Register, Mercer University College of Pharmacy

Routine moderate to strenuous exercise can strengthen the heart muscle and improve blood flow to the lungs and the rest of the body. Capillaries widen to deliver more oxygen to the tissues, and allow more toxins to be removed. [1] Risk for cardiovascular disease, the leading cause of death in the United States, can be decreased with diet modifications and physical activity. The American Heart Association recommends at least 150 minutes of moderate-intensity aerobic activity or at least 75 minutes of vigorous-intensity aerobic activity per week. [2] Studies have also been conducted to look for relationships between physical and mental health, and correlations may have been found between continued regular exercise and a decrease in major depressive disorder symptoms. Dementia is a disease characterized by progressive deterioration of cognitive function, and may be the most prevalent neurodegenerative disease in the world. Researchers continue to search for links between physical health and improved cognition. [3]

Physical Activity, Cognitive Decline, and Risk of Dementia: 28 Year Follow-up of Whitehall II Cohort Study
Design Prospective cohort; N= 10,308
Objective To test the hypothesis that physical activity in midlife is not associated with a reduced risk of dementia
Study Groups No dementia at follow-up (n= 9,979); dementia at follow-up (n= 329); following recommended 2.5 hours per week of moderate to vigorous physical activity (MVPA) (n= 5,347); not following recommended 2.5 hours per week of MVPA (n= 4,961)
Methods The Whitehall II study is an ongoing study including persons aged 35-55, recruited from 1985 to 1988, with follow-up clinical examinations approximately every five years. Physical activity was assessed using a questionnaire about frequency and duration of mild, moderate, and vigorous physical activity. “Recommended physical activity” was defined by the World Health Organization criteria of MVPA at least 2.5 hours per week. Comprehensive tracing of electronic health records was used for ascertainment of dementia.
Duration 27 years
Primary Outcome Measure Dementia diagnosis
Baseline Characteristics
No dementia at end of follow-up Dementia at end of follow-up p-value 2.5 hours per week MVPA <2.5 hours per week MVPA p-value
Mean age, years (SD) 44.8 (6.0) 50.5 (4.7) <0.001 44.5 (6.0) 45.4 (6.1) <0.001
Women, n (%) 3,269 (32.8) 144 (43.8) <0.001 1,278 (23.9) 2,135 (43.0) <0.001
University degree or higher, n (%) 2,601 (26.1) 63 (19) 0.005 1,461 (27.3) 1,203 (24.2) <0.001
Low occupational position, n (%) 2,206 (22.1) 131 (40) <0.001 816 (15.3) 1,521 (30.7) <0.001
Current smokers, n (%) 1,823 (18.1) 68 (21) 0.27 906 (16.9) 985 (19.9) <0.001
Heavy alcohol consumption*, n (%) 1,707 (17.1) 44 (13) 0.08 1,003 (18.8) 748 (15.1) <0.001
Diabetes, n (%) 90 (0.9) 10 (3) <0.001 37 (0.7) 63 (1.3) 0.003
Hypertension, n (%) 1,876 (18.8) 93 (28) <0.001 977 (18.3) 992 (20.0) <0.001
Cardiovascular disease, n (%) 116 (1.2) 6 (2) 0.28 58 (1.1) 64 (1.3) 0.33

*Defined as ≥14 units per week in women and ≥21 units per week in men

Results
Cases of dementia/total Hazard ratio adjusted for age/sex (95% CI) Hazard ratio adjusted for social/ behavioral factors* (95% CI) Hazard ratio fully adjusted‡ (95% CI)
Total physical activity (TPA) <8 hours per week, n 142/4,285 1.00 1.00 1.00
TPA 8-12 hours per week, n 71/2,451 0.89 (0.67 to 1.18) 0.94 (0.71 to 1.26) 0.97 (0.72 to 1.29)
TPA ≥12 hours per week 116/2,572 1.03 (0.80 to 1.32) 1.06 (0.82 to 1.36) 1.05 (0.82 to 1.36)
MVPA <2.5 hours per week 172/4,961 1.0 1.0 1.0
MVPA >2.5 hours per week 157/5,347 1.0 (0.80 to 1.24) 1.08 (0.86 to 1.36) 1.07 (0.86 to 1.35)

*Adjusted for age, sex, ethnicity, education, occupational position, marital status, smoking status, alcohol consumption, and fruit and vegetable consumption

‡Additionally adjusted for hypertension, diabetes, body mass index, General Health Questionnaire score, cardiovascular disease, and cardiovascular disease drugs

Adverse Events Common Adverse Events: N/A
Serious Adverse Events: N/A
Percentage that Discontinued due to Adverse Events: N/A
Study Author Conclusions No evidence was found of a neuroprotective effect of physical activity. Hours per week of physical activity was not shown to differ in dementia cases and non-cases between 28 and 10 years prior to diagnosis; however, physical activity was shown to decline within nine years prior to diagnosis, possibly due to preclinical symptoms of dementia.

 

Dementia is a progressive disorder that involves changes over a long pre-clinical period, which is why this study has thus far collected data from patients over a mean duration of 27 years. Physical activity was broken down into total hours of varying exercise intensities per week, as well as both reaching and not reaching World Health Organization recommended 2.5 hours of moderate to severe physical activity per week. While no neuroprotective effects of physical activity have been found here, there are still numerous health benefits to regular physical exercise.  In an aging population of rising life expectancy, diseases like dementia are expected to continue to increase. Following recommended weekly exercise can continue to decrease risks of other diseases known to increase mortality.

 

References

[1] Benefits of Physical Activity. U.S. Department of Health and Human Services: National Institutes of Health: National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov. June 2016.

[2] Lanier JB, Bury DC, Richardson SW. Diet and Physical Activity for Cardiovascular Disease Prevention. Am Fam Physician. 2016;93(11):919-24.

[3] Matta mello portugal E, Cevada T, Sobral monteiro-junior R, et al. Neuroscience of exercise: from neurobiology mechanisms to mental health. Neuropsychobiology. 2013;68(1):1-14.

[4] Sabia S, Dugravot A, Dartigues JF, et al. Physical activity, cognitive decline, and risk of dementia: 28 year follow-up of Whitehall II cohort study. BMJ. 2017;357:j2709.

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