Fitness, strength and severity of COVID-19: a prospective register study of 1 559 187 Swedish conscripts
af Geijerstam et al.,
Fitness, strength and severity of COVID-19: a prospective register study of 1 559 187 Swedish conscripts,
BMJ Open, doi:10.1136/bmjopen-2021-051316
Prospective study of 1,559,187 men in Sweden with cardiorespiratory fitness levels measured on military conscription, showing high cardiorespiratory fitness associated with lower risk of COVID-19 hospitalization, ICU admission, and death.
risk of death, 50.0% lower, OR 0.50, p = 0.005, high vs. low fitness, model 7, RR approximated with OR.
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risk of ICU admission, 40.0% lower, OR 0.60, p < 0.001, high vs. low fitness, model 7, RR approximated with OR.
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risk of hospitalization, 27.0% lower, OR 0.73, p < 0.001, high vs. low fitness, model 7, RR approximated with OR.
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Effect extraction follows pre-specified rules prioritizing more serious outcomes. Submit updates
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af Geijerstam et al., 5 Jul 2021, prospective, Sweden, peer-reviewed, 9 authors, study period March 2020 - September 2020.
Contact:
eijerstam@gu.se.
Abstract: Open access
Original research
Agnes af Geijerstam ,1 Kirsten Mehlig,1 Mats Börjesson,2,3
Josefina Robertson,1,4 Jenny Nyberg ,5 Martin Adiels,1,2 Annika Rosengren,2,6
Maria Åberg,1,7 Lauren Lissner1
To cite: af Geijerstam A,
Mehlig K, Börjesson M, et al.
Fitness, strength and severity
of COVID-19: a prospective
register study of 1 559 187
Swedish conscripts. BMJ Open
2021;11:e051316. doi:10.1136/
bmjopen-2021-051316
►► Prepublication history and
additional supplemental material
for this paper are available
online. To view these files,
please visit the journal online
(http://dx.doi.o rg/10.1136/
bmjopen-2021-051316).
Received 15 March 2021
Accepted 16 June 2021
© Author(s) (or their
employer(s)) 2021. Re-use
permitted under CC BY.
Published by BMJ.
For numbered affiliations see
end of article.
Correspondence to
Dr Agnes af Geijerstam;
agnes.af.g eijerstam@gu.se
ABSTRACT
Objective To investigate the possible connection between
cardiorespiratory fitness (CRF) and muscle strength in
early adulthood and severity of COVID-19 later in life.
Design Prospective registry-based cohort study.
Participants 1 559 187 Swedish men, undergoing
military conscription between 1968 and 2005 at a mean
age of 18.3 (SD 0.73) years.
Main outcome measures Hospitalisation, intensive care
or death due to COVID-19 from March to September 2020,
in relation to CRF and muscle strength.
Results High CRF in late adolescence and early adulthood
had a protective association with severe COVID-19 later in
life with OR (95% CI) 0.76 (0.67 to 0.85) for hospitalisation
(n=2 006), 0.61 (0.48 to 0.78) for intensive care (n=445)
and 0.56 (0.37 to 0.85) for mortality (n=149), compared
with the lowest category of CRF. The association remains
unchanged when controlled for body mass index (BMI),
blood pressure, chronic diseases and parental education
level at baseline, and incident cardiovascular disease
before 2020. Moreover, lower muscle strength in late
adolescence showed a linear association with a higher risk
of all three outcomes when controlled for BMI and height.
Conclusions Physical fitness at a young age is associated
with severity of COVID-19 many years later. This
underscores the necessity to increase the general physical
fitness of the population to offer protection against future
viral pandemics.
BACKGROUND
The COVID-19 pandemic has affected
the world in unprecedented ways. While
measures such as contact restrictions and
vaccinations relieve the immediate impact
of the disease, epidemiological studies may
identify risk factors that could be managed in
the long run, in order to reduce the impact
of future epidemics. Early on, advanced age
and current cardiovascular comorbidities
including obesity were found to be associated
with a more severe course of COVID-19.1–3
Cardiorespiratory fitness (CRF) is regarded
as one of the most important risk factors
for overall health, cardiovascular morbidity
and overall mortality.4 The level of physical
Strengths and limitations of this study
►► Data from the Swedish military service conscription
registry provided us with objective measures of fitness in a uniquely large sample.
►► The prospective design with long and near-complete
follow-up from well-validated hospital records and
the death registry gives a strong ground for drawing
conclusions.
►► Limitations include thatit was not possible to distinguish conscripts with low versus extremely low
fitness levels.
►► Since female conscription was..
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