Does a ‘strong’ immune system ward off colds and flu?

Q: I’m a woman in my 60s and hardly ever get sick. A cold or (sometimes persistent) cough maybe every two years, the occasional bout of what might be food poisoning, but I have never had the flu and can’t remember the last time I took a sick day. Am I just lucky? Is my immune system “strong,” and what does that mean? And is there anything I can do to keep my luck going?

A: What makes people sick is a combination of bad luck — exposures to viruses or other pathogens — and the state of their immune system, said Dr. Talia Swartz, an assistant professor and infectious disease expert at the Icahn School of Medicine at Mount Sinai in New York. Someone with a weakened immune system is likely to be more vulnerable to passing bugs than someone with a healthy one.

“There are definitely different types of patients who are more resistant to infections or who have slower progression of infectious diseases based on certain immune features we recognize that make them have a stronger immune system,” she said.

The difference may be genetic, though the specifics aren’t well understood, said Dr. Pritish Tosh, an infectious diseases researcher at the Mayo Clinic in Rochester, Minn. Someone might have a particular genetic ability to generate antibodies against certain types of viruses like the flu, for instance, he said.

A healthful lifestyle clearly boosts the immune system, Tosh said, while the opposite is also true: Practicing unhealthy habits like not getting enough sleep, a poor diet and lack of exercise can weaken the immune system.

Smoking, or even living with a smoker, can also cause structural damage to the lungs, and could make someone more vulnerable to certain infectious diseases, he said.

People with unhealthy habits may also be hurting their ability to recover from illness, Tosh said. Obesity is a predictor of complications from the flu, for instance.

Frequent hand washing is also crucial for keeping bugs from entering the mouth, nose and eyes, where they can spread infections, Swartz said.

She also recommends annual flu shots to attempt to prevent flu or reduce its severity.

Other vaccinations, like the new shingles vaccine, which is now recommended for people 50 and older, are also a good idea to help the immune system.

The immune system’s responsiveness typically declines with age, making older people more vulnerable to many pathogens than they were in their younger days.

The bottom line, Tosh said, is that a baseline of good health helps keep the immune system strong.

“If someone is eating well, exercising, getting a good amount of sleep and avoiding unnecessary stresses, they are less likely to get ill, and if they do get ill, have better outcomes,” he said.