The aging of the immune system involves a series of changes which decrease the ability to fight off infections and increase chronic low-grade inflammation [1]. These changes can promote chronic age-related diseases, including Alzheimer’s disease. The immune system can affect cognition, and the majority of genes shown to influence Alzheimer’s disease risk impact the function of the immune system [2]. This suggests that aging-related changes to the immune system may impact the risk and rate of cognitive decline, and that maintaining a healthy immune system could help stave off dementia.
A study involving residents of Baltimore, Maryland examined the relationship between the aging of the immune system and cognitive decline [3]. They found that accelerated aging of the immune system was associated with a greater degree of cognitive decline on measures of visual memory and attention/speed of processing in men. The stronger effect in men is consistent with evidence that the function of immune cells is maintained for a longer period of time in women, and that the immune cells in men show greater levels of the aging-related changes known to drive inflammation [4].
These changes in immune system function are not an inevitable part of getting older. The aging-related remodeling of the immune system is primarily driven by changes to metabolism, the processes by which our bodies produce energy [1]. All the cells in our bodies, including our immune cells require energy to function properly, so immune cells become dysfunctional when our energy making metabolic processes slow down. Consequently, people with metabolic syndromes are more likely to show signs of accelerated immune system aging [5]. Therefore, we can keep our immune system healthy by boosting our metabolism through the lifestyle interventions of diet and exercise.
Numerous observational studies have shown that physically active people of any age have better immune responses to vaccinations and less chronic inflammation [6]. In the short-term, exercise boosts the ability of the immune system to find and fight off pathogens, while in the long-term, exercise has anti-inflammatory effects which can prevent the chronic low-grade inflammation typically associated with aging. However, it should be noted that these protective effects are only found with consistent moderate intensity exercise. Excessive levels of exercise can cause too much stress on the body, which weakens the immune system. The World Health Organization recommends getting 150 minutes of moderate intensity aerobic exercise per week [7].
Diet is also critical for maintaining a healthy immune system, since our metabolic processes break down the food we eat to produce the energy our bodies need. We need adequate amounts of vital nutrients, such as vitamins and minerals, for our metabolic processes to function optimally. Therefore, we can improve our metabolism by eating the right foods. Additionally, during the process of breaking down food our bodies produce substances called metabolites that can affect immune system function; some promote protective immunity, while others promote inflammation [8]. Different foods generate different metabolites, so it is possible to enrich our bodies with immune boosting metabolites by eating the right foods. A study examining the relationship between diet and immune system aging found that people who had diets high in fish and vegetables showed lower levels of immune cell aging as they got older [5].
WHAT YOU CAN DO
Eating a healthy diet and getting regular physical activity can help maintain a strong immune system, which may promote the long-term health of both brain and body at every age.
Betsy Mills, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Mills came to the ADDF from the University of Michigan, where she served as the grant writing manager for a clinical laboratory specializing in neuroautoimmune diseases. She also completed a Postdoctoral fellowship at the University of Michigan, where she worked to uncover genes that could promote retina regeneration. She earned her doctorate in neuroscience at Johns Hopkins University School of Medicine, where she studied the role of glial cells in the optic nerve, and their contribution to neurodegeneration in glaucoma. She obtained her bachelor's degree in biology from the College of the Holy Cross. Dr. Mills has a strong passion for community outreach, and has served as program presenter with the Michigan Great Lakes Chapter of the Alzheimer's Association to promote dementia awareness.
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