How Exercise and Sleep Support Immune Function With Age

Alyssa Jasmine had a question about immune health. She says, "Peter Attia has stated that he thinks he should have added immune health to the content of his book. It appears that immune health decreases drastically with age. Is there something that can be done?"

Yes, there are things we can do to improve immune aging. First and foremost is exercise. It is one of the most powerful tools we have to counteract age-related declines in immune function.

There was a fascinating trial in older adults who did moderate-intensity aerobic exercise three times a week for about 10 months. At the end of the study, when they received a flu vaccine, their antibody responses were significantly higher than those of sedentary controls. Their immune systems behaved more like those of younger adults. Vigorous exercise would also help, but it is harder to get older adults to do a lot of vigorous exercise, particularly if they have been sedentary.

Long-term observational studies tell a similar story. A large Finnish study followed more than 2,000 people for about two decades and objectively measured cardiorespiratory fitness. People with higher cardiorespiratory fitness had about a 25 percent lower risk of developing pneumonia. It is valuable that fitness was measured rather than estimated with a questionnaire.

At the cellular level, substantial mechanistic evidence shows that physical activity may slow immunosenescence, which is the senescence of immune cells. Senescent immune cells no longer function properly. They don't necessarily die, but remain in the body and can secrete inflammatory cytokines. That leaves fewer functional immune cells, including T cells and B cells, and contributes to immune aging.

Lifelong exercisers have fewer senescent T cells. T cells are white blood cells that have important roles in the adaptive immune system. When they become senescent, they lose their ability to divide and function effectively. They remain in the body and contribute to low-grade chronic inflammation. Active people seem to have fewer of these cells and a healthier balance of naive T cells, which respond to infections the body has not encountered before.

Exercise also boosts the activity of natural killer cells. These cells target virus-infected cells and cancerous cells, making them part of the first line of defense against cancer. Exercise mobilizes them quickly. About 70 seconds of brisk stair climbing can raise the number of circulating natural killer cells sixfold.

This helps explain why exercise is important in cancer prevention. I discussed with Dr. Kerry Courneya how exercise can be used as an adjunct to cancer treatment. Vigorous-intensity exercise was important in studies of cancer recurrence and cancer mortality. Among people who had cancer, more exercise was associated with better outcomes. Exercise is important for long-term immune surveillance against infections and cancer.

Physical activity acutely raises inflammatory markers such as IL-6 and C-reactive protein, but it produces a stronger anti-inflammatory response. Over the long term, it lowers these chronic inflammatory signals, which can accelerate aging and immune aging. Resistance training increases immune-cell activity in young and older adults, but aerobic exercise at moderate or vigorous intensity appears especially important for immune regulation, naive T-cell numbers, and natural killer cells.

The practical takeaway is straightforward. If older adults can meet the moderate-intensity guidelines and add one or two sessions of vigorous exercise, they will be in good shape. Aerobic exercise is a reliable, low-risk way to support the immune system, brain, cardiovascular system, heart, lungs, and respiratory fitness. Resistance training and muscular health are also important, but aerobic exercise is key for many of these systems.

Sleep also regulates immune aging. We should get seven to nine hours of good sleep. People normally wake around 10 times a night and usually do not remember it. Remembering frequent awakenings can be a sign of more fragmented sleep.

Sleep duration relates to vaccination response. People who sleep fewer than six hours a night and receive a flu shot have a weaker antibody response than those who get seven to nine hours. In another study, older adults who reported high daytime sleepiness had lower antibody titers after a flu vaccine. These findings are correlational, but multiple lines of evidence strengthen the case for adequate sleep and a robust antibody response.

The evidence is not limited to vaccines. In one study, participants were deliberately exposed to a cold virus. Those who slept less than five hours a night were about 4.5 times more likely to develop a cold than people sleeping seven or more hours. That is a large increase in susceptibility from inadequate sleep and one of the strongest data sets I have seen.

Mechanistically, this makes sense. Deep, restorative sleep supports the production and training of T cells, which recognize and attack viruses. Sleep supports the creation of naive T cells and the activation of existing cells. It is important for preventing infections and reducing their severity. Prioritize seven to nine hours, particularly during winter when cold and flu viruses circulate more. If you must choose between partying and sleep, choose sleep, especially during that time of year.

Stress management is another factor. Chronic psychological stress is probably one of the most underappreciated accelerators of immune aging. I am not talking about an acute increase in cortisol. Chronic emotional or psychological stress keeps the body in a low-grade fight-or-flight state. Over time, it promotes chronic inflammation and suppresses immune function.

Chronic stress sustains inflammatory cytokines such as IL-6 and TNF-alpha. These signals can shorten telomeres in immune cells, promote immunosenescence, and accelerate cellular aging. It is important to find ways to become calmer and address chronic emotional, psychological, or financial stress.

We see evidence in caregivers who look after a spouse, parent, or other relative with dementia or another disabling disease. They experience high chronic stress. Compared with people who are not caregivers, they have blunted antibody responses to flu vaccination and slower wound healing, another marker of compromised immune function.

Stress-reduction strategies can be especially important for caregivers and anyone experiencing chronic emotional stress. Meditation, mindfulness, exercise, and tai chi can help. I recently visited parks in China where many older adults practice tai chi. Tai chi has been linked to better vaccine responses in older adults. There is also evidence that mindfulness training can reduce infections by about one-third. None of this is new, but it is worth revisiting.

Heat and cold exposure may also influence immune function. A large Finnish study found that people who used a sauna two to seven times per week had about a 20 percent lower risk of pneumonia than people who used it once or less. Among men who were both physically active and used the sauna, pneumonia risk was almost 40 percent lower.

Mechanistically, sauna exposure increases circulation, mobilizes white blood cells, and produces some responses similar to moderate physical activity. Heat-shock proteins also help repair cellular damage.

The evidence for deliberate cold exposure is more mixed, but there are promising data. A large randomized controlled trial included about 3,000 participants who finished their showers with 30 to 90 seconds of cold water each day for a month. They were followed for about 60 days. People who took cold showers reported 29 percent less sick leave from work, which suggests that illnesses may have been milder or shorter.

Cold exposure raises norepinephrine, one of the most consistent physiological responses to cold. Norepinephrine may activate immune cells and sharpen the stress response. There are important caveats. Prolonged or extreme cold stress can suppress immunity. Brief exposure, such as a quick cold shower or cold plunge, may be useful, but prolonged cold can have the opposite effect.

Other factors can suppress immune function. Smoking and alcohol are at the top of the list. Current smokers have about twice the risk of developing pneumonia, and former smokers have about a 50 percent higher risk. Smoking strongly affects respiratory illness, and alcohol suppresses immune function.

Nutrition is also important and may be an overlooked driver of immune decline in older adults. Many do not consume enough protein or key micronutrients. Protein and amino acids support lymphocyte counts and are associated with lower infection rates. Micronutrients such as vitamins A, C, E, B6, B12, and folate, along with zinc and selenium, serve as cofactors for immune enzymes and support lymphocyte development.

Fruits, vegetables, legumes, fish, and nuts provide many of these nutrients. A Mediterranean-style diet is consistently associated with lower inflammatory biomarkers and healthier immune function.

Several supplements may be meaningful for immune function. Vitamin D is important, especially for avoiding deficiency. Zinc, vitamin C, omega-3 fatty acids, and glutamine may also be relevant. Probiotic trials suggest reduced risk of upper respiratory tract infections and shorter illness duration. Prebiotics and probiotics may also improve vaccine responses, reflecting the connection between the gut microbiome and immune function.

Some polyphenols also show promise. In a randomized trial, healthcare workers who took green tea catechins and theanine had fewer influenza infections over the winter than a placebo group. Catechins and theanine are both found in tea, particularly green tea.

There are many things we can do to support immune aging and improve immune function in the short term. Exercise, sleep, stress management, carefully used heat or cold exposure, avoiding smoking and excessive alcohol, nutritious food, and addressing nutrient needs can all help us get sick less often.