You Asked For It: Question Authority

Nieman, David C. Dr.P.H., FACSM

doi: 10.1249/FIT.0b013e31819172ca
DEPARTMENTS: You Asked For It: Question Authority

I am 67 years old, prone to getting sick a lot and hoping that a walking program can help. What is the connection between exercise, immune function, and illness for my age group?

David C. Nieman, Dr.P.H., FACSM, is professor and director of the Human Performance Laboratory, Appalachian State University in Boone, North Carolina; an active researcher; and author of several textbooks on health and fitness. Email your questions to

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A: I encourage you to begin walking on a near-daily basis, gradually building up to at least 30 minutes per session. Studies performed by my research team have shown that a regular exercise program during 12 weeks by elderly subjects lowers sick days with the common cold by more than half (Figure 1) (5). This reduction in illness was achieved by walking briskly for 30 to 40 minutes per session, 5 days a week. This level of physical activity is attainable by most elderly individuals.

We also showed that, during each walking bout, important immune cells such as neutrophils and natural killer cells increase their circulation throughout the body, providing enhanced protection from viruses (6,7). However, within 3 hours after each 30 to 45 minute brisk walking bout, these immune cells return to preexercise levels. Of interest is the consistent finding that the elderly recruit immune cells to the blood compartment during exercise in a similar fashion to that of younger adults (1,2). The key concept is that near-daily activity is needed to gain this acute immune benefit of enhanced recirculation of immune cells.

As people age, the immune system does not function as well, and this decline is partly responsible for some of the afflictions of old age (8). For example, elderly persons are more susceptible to vaccine failure, a variety of infectious diseases including influenza and pneumonia, autoimmune disorders, and cancers when compared with younger adults. This age-related downturn in immune function is most apparent for T cells, a special type of white blood cell that regulates much of the immune system. In comparison with the T cells from young persons, those from the elderly individuals function only half as well (5).

Older adults exercise less and have lower levels of aerobic fitness than younger adults, and recent studies indicate that this may contribute to the decline of immune function. The good news is that becoming lean and aerobically fit has multiple immune benefits for the elderly. One study showed that T cell function in thin and aerobically fit elderly women was superior to that of their sedentary overweight peers and equal to women approximately half their age (5). Natural killer cell function, an important component of the innate or frontline immune system, also was augmented in the aerobically fit elderly subjects. This translated to a much lower rate of illness from upper respiratory tract infections such as the common cold (8% for the fit subjects and 50% for sedentary controls during a 12-week period). Other studies confirmed that regular physical activity confers immune benefits for the elderly (3,9).

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Vaccine efficacy or the ability to produce a sufficient quantity of protective antibodies is a major concern among the elderly. The influenza vaccine is only 31% to 65% effective in countering the flu among older adults compared to 68% to 88% in younger adults (3). Thus, a significant number of older adults may not develop protective antibody levels after immunization. A 10-month exercise training study showed that the antibody response to the influenza vaccine was increased in elderly adults compared with sedentary controls (3) (Figure 2). The exercise subjects trained moderately at 65% to 75% heart rate reserve, 25 to 30 minutes, 3 days per week. Another 10-month training study with elderly subjects showed a significant reduction in inflammatory measures including interleukins 6 and 18 and C-reactive protein compared with controls (4). These data add to the growing consensus that moderate exercise training helps to improve vaccine efficacy and counter chronic low-grade inflammation in the elderly.

Collectively, these data provide strong support for the role of regular physical activity as therapy to offset at least part of the decline in immune function with advancing age. Elderly individuals who are committed to a near-daily regimen of moderate physical activity respond better to influenza vaccines, experience fewer sick days, and have an enhanced recirculation of disease-fighting immune cells. There are many other benefits of regular physical activity for the elderly including improved muscle tone, strength, and heart function; decreased risk of heart disease; enhanced control of high blood pressure; reduced body fat; decreased risk of certain types of cancers; and enhanced mental function and health. Of all age groups, the elderly have the most to benefit from regular physical activity. No medication has the power and widespread positive effects of physical activity.

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© 2009 American College of Sports Medicine