Correlates of cardiorespiratory fitness in a population-based sample of middle-aged adults: cross-sectional analyses in the SCAPIS study

Maintaining or increasing cardiorespiratory fitness is associated with reduced hospital admission rate

AIMS

The aim of this study was to investigate the association between change in cardiorespiratory fitness (CRF) and cardiovascular disease (CVD)-related and all-cause hospital admission and explore if the association varies dependently on prior admission, baseline CRF, sex, and age.

METHODS AND RESULTS

A total of 91 140 adult participants (41.5% women) with two examinations from occupational health profile assessments between 1986 and 2019 were included (mean of 3.2 years between examinations). Cardiorespiratory fitness was assessed as maximal oxygen consumption and estimated through a submaximal cycle test. Cardiorespiratory fitness change was defined as annual percentage change in relative CRF (mL/min/kg) and further divided into 'decliners' (≤1%), 'maintainers' (-1% to 1%), and 'increasers' (>1%). Hospital admissions were followed over a mean of 7 years. Natural cubic splines and Cox proportional hazards model were applied. Additionally, prevented fraction for the population was calculated. Increase in CRF was associated with a lower risk of CVD [hazard ratio (HR) = 0.99] and all-cause hospital admission (HR = 0.99), after multilevel adjustment for confounders and change in smoking, diet, and stress. Compared with a decline, maintenance of CRF was associated with 9% and 7% lower risk of CVD and all-cause admission, respectively. Increase in CRF reduced the risk by 13% and 11% and, for individuals with prior admission, by 20% and 14%. The burden of CVD and all-cause admission was 6% and 5% lower than if the whole cohort had declined CRF, with large potential cost savings.

CONCLUSION

Efforts to maintain or improve CRF should be included in disease-preventive strategies, regardless of change in other lifestyle-related risk factors. Preventing the age-associated decline in CRF can lessen healthcare utilization and costs.

Associations between physical activity and autonomic function during deep breathing test: the Swedish CArdioPulmonary bioImage Study (SCAPIS)

PURPOSE

The deep breathing test (DBT) is a sensitive test of cardiovagal function. The aim of this study was to explore associations between physical activity and sedentary time, measured by accelerometer, and autonomic function, using DBT.

METHODS

In the Swedish Cardio-Pulmonary bioImage Study, men and women aged 50-64 were randomly invited from the general population. A total of 4325 subjects who underwent DBT and assessment of physical activity and sedentary time by accelerometery were included. ECG files from 1-min DBT were used to calculate measures of respiratory sinus arrhythmia [RSA; expiration-inspiration (E-I) difference and E/I ratio], heart rate variability [HRV; root mean square of successive differences (RMSSD), standard deviation of heart rates and mean circular resultant]. Low RSA and HRV was defined as the lowest 10% in the population.

RESULTS

For accelerometer-assessed physical activity, there were significant associations between high percentage of sedentary time and low E/I (p < 0.01), and low RMSSD (p < 0.01) in an age- and sex-adjusted model, and between percentage of sedentary time and low RMSSD (p = 0.04) in a risk factor-adjusted model. Low RMSSD was less common in those with a high percentage of moderate to vigorous physical activity (p = 0.04, after risk-factor adjustment). These associations became non-significant when further adjusting for heart rate.

CONCLUSION

We report associations between degree of physical activity and indices of autonomic dysfunction in a large population. The relationships were no longer significant after adjustments for heart rate, indicating that the relationship between physical activity and cardiovagal function partly is accounted for by reduced heart rate.