Bodily health at a younger age linked to safety towards extreme COVID-19
Of late teenage Swedish men who performed well on conscription physical aptitude tests, a relatively high proportion were able to avoid hospital treatment when they contracted COVID-19 during the pandemic up to 50 years later. This has been shown by researchers from the University of Gothenburg in a registry study, the results of which have now been published in the BMJ Open.
The study is based on the Swedish Conscription Register, which contains information on over 1.5 million young Swedish men who began their military service between 1969 and 2005. Almost all of these men then took both a bike test and a strength test. Around 2,500 of the men entered in the conscription register were later admitted to hospital with COVID-19 in spring 2020.
Merging of registers
For their study, the scientists divided the men into three groups based on their results in the fitness and strength tests. The data were merged with three other Swedish registers: the National Register for Inpatients (IPR, also known as the Hospital Discharge Register), the Intensive Care Register and the Causes of Death register. The results show a clear association between fitness and strength in adolescents and the risk of hospital treatment for COVID-19 infection 15–50 years after being drafted.
At the population level, we can see that both good fitness and good muscle strength in late teens are protective factors for severe COVID. For people in good fitness at the time of conscription, the risk of death in spring 2020 was half as high as for the least fit. We also see a similar protective effect for those whose strength was good back then. ”
Agnes af Geijerstam, PhD student, Sahlgrenska Academy, Gothenburg University, lead author of the study
However, because the oldest men in the study had not yet reached the age of 70, deaths from COVID-19 in the study were rare.
Protective effect regardless of obesity
The conscription register also contains information on the height and weight of the young men.
“Previous studies have shown obesity to be a risk factor for severe COVID. But we see that good fitness and strength are protective factors for everyone, including men who are overweight or obese, ”says Professor Lauren Lissner, lead co-author of the study.
The study also showed a link between men’s height and the risk of COVID-19 infection.
“The taller the men, the greater their risk of needing advanced care if they had COVID. but per centimeter this increase in risk is very small. In addition, in contrast to fitness and strength, there is no way to influence our body size, ”says af Geijerstam.
Strengthening the immune system
There are already many studies showing the protective effects of good physical fitness in a wide range of diseases, including infections. It has been found that physical activity strengthens the immune system and reduces the tendency towards inflammation. Adolescent fitness is also likely to be associated with an active and otherwise healthy lifestyle throughout adult life.
“It’s interesting to see that these men’s high fitness and strength levels can be linked to protection from severe COVID so many years ago. Today, young people are becoming more sedentary, which means they are at risk of bigger problems in the long run – including less resistance to future virus pandemics. Children and young people must have sufficient freedom of movement, ”says af Geijerstam.
af Geijerstam, A., et al. (2021) Fitness, Strength, and Severity of COVID-19: a prospective registry study of 1,559,187 Swedish conscripts. BMJ open. doi.org/10.1136/bmjopen-2021-051316.