Among Swedish men in their late teens who did well on physical fitness tests for military conscription, a relatively high proportion were able to avoid hospital care when they were infected with COVID-19 during the pandemic until 50 years later. This was demonstrated by researchers at Gothenburg University in a registry study, the results of which are now published in the BMJ Open.
The study is based on the Swedish conscription register, which contains information on more than 1.5 million young Swedish men who began their military service in the years 1969-2005. Almost all of these men then underwent both a bike test and a strength test. Some 2,500 of the men included in the conscription register were later, in the spring of 2020, hospitalized with COVID-19.
Merging of registers
For their study, the scientists divided the men into three groups based on their fitness and strength test scores. The data was merged with three other Swedish registries: the National Inpatient Register (IPR, also known as the Hospital Discharge Register), the Intensive Care Register and the Cause of Death Register. The results show a clear association between fitness and strength in young people and the risk of needing hospital care for COVID-19 infection 15 to 50 years after conscription.
At the population level, we can see that good physical shape and muscle strength in late adolescence are protective factors against severe COVID. For those who were in good physical shape at the time of conscription, the risk of dying in the spring of 2020 was half that of the less fit. For those whose strength was good at the time, we also see a similar protective effect. ”
Agnes af Geijerstam, PhD student, Sahlgrenska Academy, University of Gothenburg, lead author of the study
However, since the oldest men in the study had not reached the age of 70, deaths from COVID-19 were rare in the study.
Protective effect regardless of overweight
The conscription register also contains data on the height and weight of young men.
âPrevious studies have shown obesity to be a risk factor for severe COVID. But we see that good physical shape and strength are protective factors for everyone, including overweight and obese men, âsays Professor Lauren Lissner, co-lead author of the study.
In addition, the study showed a link between the height of men and the risk of infection with COVID-19.
âThe older the men, the more likely they were to need advanced care when they contracted COVID; but per centimeter, this increase in risk is very small. Also, unlike fitness and strength, there is no way to influence our height, âsays af Geijerstam.
Boost the immune system
There have already been many studies showing the protective effect of being in good physical condition in many medical conditions, including infections. It has been shown that the immune system is strengthened and the propensity for inflammation is reduced by physical activity. Fitness in adolescence is also likely to be associated with active and otherwise healthy lifestyles throughout adulthood.
âIt’s interesting that the high levels of fitness and strength that these men had so many years ago may be linked to protection from severe COVID. Today, young people are becoming increasingly sedentary, which means there is a risk of major long-term problems, including reduced resistance to future viral pandemics. Children and adolescents must be given enough freedom to move around, âaf Geijerstam says.
af Geijerstam, A., et al. (2021) Physical form, strength and severity of COVID-19: a prospective study of the register of 1,559,187 Swedish conscripts. BMJ Open. doi.org/10.1136/bmjopen-2021-051316.