It is well-known that physical activity can affect the immune system and, in some cases, make people more resistant to viral infections. A year-long study that looked at whether a similar effect applies for bacterial infections has recently been released. While the study suggests that some sort of protective benefit is present, the strength and reliability of the finding is hampered by the structure of the study itself.
In Brief: Why the Danes?
Denmark is unique for medical research because the country’s civil registration numbers make finding certain correlations easier. A civil registration number is given to all citizens at birth, and connects with various nationwide registries. In this case, the researchers used the registration numbers to connect the survey results of individual Danes with prescription histories.
The researchers looked at the leisure-time physical activity data for 18,874 Danes that was taken during regional health surveys, and followed up with them in one year. They were considered to have a bacterial infection if they had received a prescription for antibiotics. The following observations were made:
- During the follow-up period, 5,368 participants filled at least one antibiotic prescription
- There was a statistically significant difference between physical activity and antibiotic prescriptions in women, but not men
- When compared with sedentary behavior, any level of physical activity showed a decrease in antibiotic prescriptions (average decrease was 10%)
- Most of the antibiotics were for cystitis (type of urinary tract infection)
- Among the cystitis antibiotics, low-levels of physical activity were tied to a 21% decrease, and moderate activity was correlated to a 32% decrease
- Interestingly, there seemed to be no effect related to antibiotics associated with respiratory infections
What This Means
Speaking broadly, the study suggests that low or moderate levels of physical activity could help protect women from bacterial infections, specifically bacterial UTIs. High/vigorous levels may actually be counterproductive, since intense physical activity is known to increase vulnerability to certain types of infection.
However, the filling of antibiotic prescriptions is not the best measure for bacterial infections. For instance, any of the following situations could distort the results:
- Simply not taking medicine and “toughing it out”
- Taking previously-filled antibiotics or over-the-counter medications
- Getting an antibiotic prescription for what is actually a viral infection (annoyingly common in respiratory ailments)
- Being given a sample the physician had on hand from a drug rep
- Any instance where antibiotics are prescribed as a precaution or preventative measure rather than to treat a known infection
The authors, to their credit, acknowledge some of these issues. It is certainly plausible that physical activity helps protect against some bacterial infections, but unfortunately the reliability of this study’s findings is hampered by too many unknowns.
Pape, K., et. al., “Leisure-Time Physical Activity and the Risk of Suspected Bacterial Infections,” Medicine & Science in Sports & Exercise, 2016; 10.1249/MSS.0000000000000953.