Gymnastik- och idrottshögskolan, GIH

AIMS: Submaximal tests estimating VO₂max have inherent biases; hence, using VO₂max estimations from the same test is essential for reducing this bias. This study aimed to establish sex- and age-specific reference values for estimated VO₂max using the Åstrand-test (Å-test) and the Ekblom-Bak test (EB-test). We also assessed the effects of age, exercise level, and BMI on VO₂max estimations.

METHODS: We included men and women (20-69 years) from the Swedish working population participating in Health Profile Assessments between 2010 and 2020. Excluding those on heart rate-affecting medicines and smokers, n = 263,374 for the Å-test and n = 95,043 for the EB-test were included. VO₂max reference values were based on percentiles 10, 25, 40, 60, 75, and 90 for both sexes across 5-year age groups.

RESULTS: Estimated absolute and relative VO₂max were for men 3.11 L/min and 36.9 mL/min/kg using the Å-test, and 3.58 L/min and 42.4 mL/min/kg using the EB-test. For women, estimated absolute and relative VO₂max were 2.48 L/min and 36.6 mL/min/kg using the Å-test, and 2.41 L/min and 35.5 mL/min/kg using the EB-test. Higher age (negative), higher exercise level (positive), and higher BMI (negative) were associated with estimated VO₂max using both tests. However, explained variance by exercise on estimated VO₂max was low, 10% for the Å-test and 8% for the EB-test, and moderate for BMI, 23% and 29%.

CONCLUSION: We present reference values for estimated VO₂max from two submaximal cycle tests. Age, exercise, and BMI influenced estimated VO₂max. These references can be valuable in clinical evaluations using the same submaximal tests.

Sickness absence from work has a large adverse impact on both individuals and societies in Sweden and the costs for sickness absence were calculated to 64.6 billion Swedish kronor (approx. 5.6 billion in Euros) in 2020. Although high cardiorespiratory fitness may protect against potential adverse effects of high physical workload, research on the moderating effect of respiratory fitness in the relation between having an occupation with high physical workload and sickness absence is scarce. To study the moderating effect of cardiorespiratory fitness in the association between occupation and psychiatric, musculoskeletal, and cardiorespiratory diagnoses. Data was retrieved from the HPI Health Profile Institute database (1988-2020) and Included 77,366 participants (mean age 41.8 years, 52.5% women) from the Swedish workforce. The sample was chosen based on occupational groups with a generally low education level and differences in physical workload. Hurdle models were used to account for incident sickness absence and the rate of sickness absence days. There were differences in sickness absence between occupational groups for musculoskeletal and cardiorespiratory diagnoses, but not for psychiatric diagnoses. In general, the association between occupation and musculoskeletal and cardiorespiratory diagnoses was moderated by cardiorespiratory fitness in most occupational groups with higher physical workload, whereas no moderating effect was observed for psychiatric diagnoses. The study results encourage community and workplace interventions to both consider variation in physical workload and to maintain and/or improve cardiorespiratory fitness for a lower risk of sickness absence, especially in occupations with high physical workload.

The main aim of this thesis was to study cardiorespiratory fitness, physical workload, and lifestyle-related factors, with a special emphasis on cardiorespiratory fitness in an occupational context and the associations with cardiovascular disease and sickness absence across a wide range of occupations. A secondary aim was to study trends in cardiorespiratory fitness in different occupational groups over the last decades.

The thesis is based on data from health profile assessments performed in the Swedish working population over the last decades and consists of four studies. Paper I examines health risk factors across a diverse range of occupational groups and finds that high-skilled occupations have a more favorable health risk profile than low-skilled occupations, with some sub-major categories displaying a more unfavorable health risk profile than others. Paper III demonstrates that individuals in low-skilled and blue-collar occupations have a significantly higher risk of incident cardiovascular disease than high-skilled white-collar workers. Cardiorespiratory fitness, smoking, and body mass index partially explain this association. Paper IV shows that occupational physical workload is associated with sickness absence, where a higher physical workload is related with a higher risk of total sickness absence due to musculoskeletal and cardiorespiratory causes but a lower risk of sickness absence due to psychiatric causes. Higher cardiorespiratory fitness is associated with reduced predicted days of sickness absence, mainly for cardiorespiratory diagnoses and musculoskeletal diagnoses, with some variations between occupational groups. Paper II finds a consistent decline in cardiorespiratory fitness from 2001 to 2020. This decline is more pronounced in low-skilled occupations, regardless of their classification as white-collar or blue-collar. Forecast analyses revealed a continuing downward trend in cardiorespiratory fitness, particularly in low-skilled occupations.

In conclusion, promoting smoking cessation, reduced obesity, and physical activities to improve cardiorespiratory fitness may reduce the disparity in cardiovascular disease incidence observed across occupational groups. The decline in cardiorespiratory fitness, particularly in low-skilled occupations, is concerning and calls for targeted interventions that can reach out to those who need it most. This could be achieved through structural and individual-level changes at the workplace and in society at large.

The main aim was to examine the association between occupational groups and incident cardiovascular disease (CVD), and to which extent associations are mediated by lifestyle-associated variables (cardiorespiratory fitness, smoking, BMI, exercise, and diet). A total of 304.702 participants (mean age 42.5 yrs., 47% women), who performed a health profile assessment in Sweden between 1982 and 2019, were included in the analyses. CVD incidence was obtained from national registers. All participants were free from CVD prior to the health profile assessment. Occupational group was defined using the Swedish Standard Classification of Occupations and analyzed separately (13 different occupational groups) as well as after aggregation into four occupational groups (white-collar high-skilled, white-collar low-skilled, blue-collar high-skilled and blue-collar low-skilled). Cardiorespiratory fitness, BMI, exercise, smoking, and diet were included as mediators and analyzed separately in single models and simultaneously in one multiple mediation model. All mediation analyses were adjusted for sex, age, length of education and calendar time. White-collar high-skilled was set as reference in all analyses. Blue-collar and low-skilled occupation had a higher risk of incident CVD compared to reference. Cardiorespiratory fitness, BMI, exercise, smoking, and diet mediated 48% to 54% of the associations between reference and the other aggregated occupational groups. In the single model, the strongest mediators were cardiorespiratory fitness, smoking and BMI. In conclusion, blue-collar and low skilled occupations had a significantly higher risk for incident CVD compared to white-collar high-skilled workers, with the association mediated to a large extent by variation in lifestyle-associated variables.

Objectives: This study aimed to identify main sex-specific correlates of cardiorespiratory fitness (CRF) in a population-based, urban sample of Swedish adults.

Design: Cross-sectional.

Setting: Multi-site study at university hospitals, data from the Gothenburg site.

Participants: A total of 5308 participants (51% women, aged 50-64 years) with a valid estimated VO2max, from submaximal cycle test, in the Swedish CArdioPulmonary bioImage Study (SCAPIS), were included.

Primary and secondary outcomes: A wide range of correlates were examined including (a) sociodemographic and lifestyle behaviours, (b) perceived health, anthropometrics and chronic conditions and (c) self-reported as well as accelerometer-derived physical activity and sedentary behaviours. Both continuous levels of estimated VO2max as well as odds ratios (OR) and confidence intervals (CI)s of low VO2max (lowest sex-specific tertile) were reported.

Results: In multivariable regression analyses, higher age, being born abroad, short education, high waist circumference, poor perceived health, high accelerometer-derived time in sedentary and low in vigorous physical activity, as well as being passive commuter, correlated independently and significantly with low VO2max in both men and women (OR range 1.31-9.58). Additionally in men, financial strain and being an ex-smoker are associated with higher odds for low VO2max (OR 2.15; 95% CI 1.33 to 3.48 and OR 1.40; 95% CI 1.09 to 1.80), while constant stress with lower odds (OR 0.61; 95% CI 0.43 to 0.85). Additionally in women, being a regular smoker is associated with lower odds for low VO2max (OR 0.64; 95% CI 0.45 to 0.92).

Conclusions: The present study provides important reference material on CRF and correlates of CRF in a general middle-aged population, which can be valuable for future research, clinical practice and public health work. If relations are causal, increased knowledge about specific subgroups will aid in the development of appropriate, targeted interventions.

AIMS: To describe time trends in combinations of cardiorespiratory fitness (CRF) and body mass index (BMI) status, and to analyse their associations with cardiovascular disease (CVD) incidence and mortality and all-cause mortality.

METHODS AND RESULTS: Prospective cohort study with data from occupational health screenings in Swedish employees, including n = 471 216 (aged 18-74 years) between 1995 and 2020, and n = 169 989 in risk analyses. Cardiorespiratory fitness was estimated from a submaximal cycle test. High CRF was defined as top quartile, and low CRF as bottom quartile. Body mass index was used to define normal weight (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), and obesity (≥30 kg/m2). Outcome data (CVD incidence and mortality, all-cause mortality) were obtained from national registers. From 1995 to 2020, the combination of obesity + low CRF increased from 2.1% to 5.3% (relative increase 154%) whereas the combination of normal weight + high CRF decreased from 13.2% to 9.3% (-30%) (both P < 0.001). Negative changes were more pronounced in men, younger ages, and non-university educated. At the end of the period, prevalence of obesity + low CRF were higher in men vs. women (3.1% vs. 2.2%), older vs. younger (3.7% vs. 1.7%), and in non-university vs. university educated (5.0% vs. 0.3%), all P-value <0.001. Having a high CRF attenuated the risk of all three outcomes in all BMI categories, especially in individuals with obesity (hazard ratio 3.90 vs. 6.67 for CVD mortality). Both a low BMI and a high CRF prolonged age of onset for all three outcomes.

CONCLUSIONS: The combination of obesity with low CRF has increased markedly since the mid-90s, with clear implications for increased CVD morbidity and mortality, and all-cause mortality.

Background: Low cardiorespiratory fitness (CRF) is a strong, independent predictor for chronic disease risk as well as lower work capacity. However, trend analyses of CRF in relation to different occupational groups are missing. Purpose: To study trends in CRF during the last 20 years and forecast possible future trends in different occupational groups of the Swedish working population. Methods: Data from 516,122 health profile assessments performed in occupational health screening between 2001 to 2020 was included. CRF was assessed as maximal oxygen consumption and estimated from a submaximal cycling test. Analyses include CRF as a weighted average per five-year period in 12 different occupational groups, and standardized proportions with low CRF (<32 ml/kg/min) in four aggregated occupational categories (white- and blue-collar, as well as low- and high-skilled). Also, adjusted annual change in CRF in the total population as well as by sex and age-group, also a forecast of future trends in CRF until 2040, are presented. Results: The largest decrease in both absolute and relative CRF were seen for Admin and customer service (-10.1% and -9.4%), Mechanical manufacturing (-6.5% and -7.8%) and Education (-4.8% and -7.3%) occupations. The greatest annual decrease was seen in Transport occupations (-1.62 ml/kg/min, 95% CI -0.190 to -0.134). Men and younger individuals (18-34 years) had in general a more pronounced decrease in CRF. All aggregated groups had an increase in the proportion with low CRF, with the greatest increase in blue-collar and low-skilled occupations, 16% to 21% relative change. Forecast analyses predict a continued downward trend of CRF, especially in low-skilled occupations of both white- and blue-collar occupational groups. Conclusion: There was a general trend of a decreasing CRF in all occupational groups, however the trend was more pronounced in blue-collar and low-skilled occupational groups. Structural changes at the workplaces and in society are needed to stop the downward trend in CRF. Funding: This work was supported by The Swedish Research Council for Health, Working Life and Welfare https://forte.se/en/ (Grant no 2018-00384) and The Swedish Heart-Lung Foundation https://www.hjartlungfonden.se/HLF/Om-Hjart-lungfonden/About-HLF/ (Grant no 20180636).

BACKGROUND: The impact of cardiorespiratory fitness (CRF) and other lifestyle-related factors on severe COVID-19 risk is understudied. The present study aims to investigate lifestyle-related and socioeconomic factors as possible predictors of COVID-19, with special focus on CRF, and to further study whether these factors may attenuate obesity- and hypertension-related risks, as well as mediate associations between socioeconomic factors and severe COVID-19 risk.

METHODS: Out of initially 407,131 participants who participated in nationwide occupational health service screening between 1992 and 2020, n = 857 cases (70% men, mean age 49.9 years) of severe COVID-19 were identified. CRF was estimated using a sub-maximum cycle test, and other lifestyle variables were self-reported. Analyses were performed including both unmatched, n = 278,598, and sex-and age-matched, n = 3426, controls. Severe COVID-19 included hospitalization, intensive care or death due to COVID-19.

RESULTS: Patients with more severe COVID-19 had significantly lower CRF, higher BMI, a greater presence of comorbidities and were more often daily smokers. In matched analyses, there was a graded decrease in odds for severe COVID-19 with each ml in CRF (OR = 0.98, 95% CI 0.970 to 0.998), and a two-fold increase in odds between the lowest and highest (< 32 vs. ≥ 46 ml·min^-1·kg^-1) CRF group. Higher BMI (per unit increase, OR = 1.09, 1.06 to 1.12), larger waist circumference (per cm, OR = 1.04, 1.02 to 1.06), daily smoking (OR = 0.60, 0.41 to 0.89) and high overall stress (OR = 1.36, 1.001 to 1.84) also remained significantly associated with severe COVID-19 risk. Obesity- and blood pressure-related risks were attenuated by adjustment for CRF and lifestyle variables. Mediation through CRF, BMI and smoking accounted for 9% to 54% of the associations between low education, low income and blue collar/low skilled occupations and severe COVID-19 risk. The results were consistent using either matched or unmatched controls.

CONCLUSIONS: Both lifestyle-related and socioeconomic factors were associated with risk of severe COVID-19. However, higher CRF attenuated the risk associated with obesity and high blood pressure, and mediated the risk associated with various socioeconomic factors. This emphasises the importance of interventions to maintain or increase CRF in the general population to strengthen the resilience to severe COVID-19, especially in high-risk individuals.

Background: Reports have indicated a negative trend in cardiorespiratory fitness (CRF) in the general population. However, trends in relation to different occupational groups are missing. Therefore, the aim of our study was to examine the trends in CRF during the last 20 years, and to provide a prognosis of future trends in CRF, in different occupational groups of Swedish workers. Methods: Data from 516,122 health profile assessments performed between 2001 to 2020 were included. CRF was assessed as maximal oxygen consumption and was estimated from a submaximal cycling test. Analyses include CRF as a weighted average, standardized proportions with low CRF (&lt;32 mL/min/kg), adjusted annual change in CRF, and forecasting of future trends in CRF. Results: There was a decrease in CRF over the study period, with the largest decrease in both absolute and relative CRF seen for individuals working in administrative and customer service (−10.1% and −9.4%) and mechanical manufacturing (−6.5% and −7.8%) occupations. The greatest annual decrease was seen in transport occupations (−1.62 mL/min/kg, 95% CI −0.190 to −0.134). Men and younger individuals had in generally a more pronounced decrease in CRF. The proportion with a low CRF increased, with the greatest increase noted for blue-collar and low-skilled occupations (range: +19% to +27% relative change). The forecast analyses predicted a continuing downward trend of CRF. Conclusion: CRF has declined in most occupational groups in Sweden over the last two decades, with a more pronounced decline in blue-collar and low-skilled occupational groups.

The COVID-19 pandemic has become a public health emergency of international concern, which may have affected lifestyle habits and mental health. Based on national health profile assessments, this study investigated perceived changes of lifestyle habits in response to the COVID-19 pandemic and associations between perceived lifestyle changes and mental health in Swedish working adults. Among 5599 individuals (50% women, 46.3 years), the majority reported no change (sitting 77%, daily physical activity 71%, exercise 69%, diet 87%, alcohol 90%, and smoking 97%) due to the pandemic. Changes were more pronounced during the first wave (April–June) compared to the second (October–December). Women, individuals &lt;60 years, those with a university degree, white-collar workers, and those with unhealthy lifestyle habits at baseline had higher odds of changing lifestyle habits compared to their counterparts. Negative changes in lifestyle habits and more time in a mentally passive state sitting at home were associated with higher odds of mental ill-health (including health anxiety regarding one’s own and relatives’ health, generalized anxiety and depression symptoms, and concerns regarding employment and economy). The results emphasize the need to support healthy lifestyle habits to strengthen the resilience in vulnerable groups of individuals to future viral pandemics and prevent health inequalities in society.

PURPOSE: The aim of this study was to validate the submaximal Ekblom-Bak test (EB-test) and the Åstrand test (Å-test) for an elderly population.

METHODS: Participants (n = 104), aged 65-75 years, completed a submaximal aerobic test on a cycle ergometer followed by an individually adjusted indirect calorimetry VO₂max test on a treadmill. The HR from the submaximal test was used to estimate VO₂max using both the EB-test and Å-test equations.

RESULTS: The correlation between measured and estimated VO₂max using the EB method and Å method in women was r = 0.64 and r = 0.58, respectively and in men r = 0.44 and r = 0.44, respectively. In women, the mean difference between estimated and measured VO₂max was - 0.02 L min^-1 (95% CI - 0.08 to 0.04) for the EB method and - 0.12 L min^-1 (95% CI - 0.22 to - 0.02) for the Å method. Corresponding values for men were 0.05 L min^-1 (95% CI - 0.04 to 0.14) and - 0.28 L min^-1 (95% CI - 0.42 to - 0.14), respectively. However, the EB method was found to overestimate VO₂max in men with low fitness and the Å method was found to underestimate VO₂max in both women and men. For women, the coefficient of variance was 11.1%, when using the EB method and 19.8% when using the Å method. Corresponding values for men were 11.6% and 18.9%, respectively.

CONCLUSION: The submaximal EB-test is valid for estimating VO₂max in elderly women, but not in all elderly men. The Å-test is not valid for estimating VO₂max in the elderly.

Background: Maximal oxygen uptake (VO2max) has a high prognostic value for CVD and all cause mortality, however the test is hard to administer and requires a maximal effort, which can be arduous for an elderly population. The submaximal Ekblom-Bak cycle ergometer test (EB test) has shown to be valid in adults, but its applicability in an elderly population is unknown. Aim: The purpose of this study was to validate the submaximal EB test and to examine its ability to detect changes in VO2max in an elderly population. Methods: The sample consisted of 108 elderly participants; aged 65-75 years (54 women, 54 men) with a measured VO2max of 1.42-3.69 L/min. 34 women and 40 men performed a retest (VO2max 1.45-3.59 L/min) after an intervention period. During the intervention, participants performed 30 training sessions over 12 weeks where they cycled for 30 min at 65-75 % of maximal heart rate. On pre- and retests participants completed a submaximal Ekblom-Bak test. Directly after participants completed an individually adjusted VO2max test on a treadmill where VO2 max was measured using indirect calorimetry. Results: For the validation of the EB-test on an elderly population there was a correlation (R) between measured and estimated VO2max of 0.64 for women and 0.47 for men, mean (95% CI) difference was 0.01 (-0.45 - 0.07) for women and -0.05 (-0.11 - 0.07) for men. Standard error of the estimate was 0.17 for women and 0.31 for men. Coefficient of variation was 10 % for women and 11 % for men. When analyzing the ability of the EB test to track change in VO2max after a 12 week training intervention there was a significant (P<0.001) average increase in estimated VO2max of 0.11 L/min for both genders (CI for women 0.06 - 0.16 and for men 0.08 - 0.15), with no change in the measured values. Changes in the estimated values were linked to a decrease of the submaximal HR on both work rates (3.0 bpm and 3.2 bpm on the standard work rate and 5.4 bpm and 6.4 bpm on the higher work rate, for women and men, respectively) Conclusion: Validity of the EB-test in a population between 65-75 years was fairly good but we found larger standard error of the estimate for the men. The higher error for men in contrast to women could be derived from a difference in change of physiological variables that affect VO2max with increasing age. Since there was no change in measured VO2max while there was an improvement in estimated VO2max after the intervention, the EB-test appears to respond to changes in fitness that are not reflected in a VO2max. Grant funding: European Research Council.