Downloaded from http://oem.bmj.com/ on April 23, 2017 - Published by group.bmj.com

Commentary

Occupational and leisure-time physical activity and coronary heart disease Andreas Holtermann1,2 Blue collar workers with high occupational physical activity (OPA) are well known to have an increased risk for cardiovascular disease. However, there are considerable knowledge-gaps about (1) if OPA impairs instead of promotes cardiovascular health like leisure time physical activity (LTPA), and (2) if workers with high OPA should be advised to be highly physically active during leisure. These questions are important for public and occupational health because A. A sizeable fraction of the working population all over the world still has high OPA B. LTPA may provide an effective preventive measure for workers with high OPA C. International recommendations and guidelines regarding OPA and cardiovascular health are lacking. The study by Harari et al1 helps to fill these research gaps. The study, on 4819 male industrial workers, showed a multiadjusted higher incidence rate of coronary heart disease (CHD) mortality and allcause mortality among men with moderate-hard OPA compared with men with none-mild OPA. In contrast, men performing high LTPA (ie, 30 min at least twice a week) had a multiadjusted reduced risk of all-cause mortality compared with men performing low LTPA. Men with the combination of moderate-hard OPA and low LTPA had the greatest risk of all-cause mortality. However, among men with moderate-hard OPA, those having high LTPA did not have a significantly reduced risk of CHD and all-cause mortality compared to those with low LTPA. This study1 has the limitation that OPA and LTPA were self-reported, which may lead to exposure misclassification, lacking measures of cardiorespiratory fitness, and the study population of industrial male workers not being representative for a whole

1

National Research Centre for the Working Environment, Copenhagen, Denmark; 2Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark Correspondence to Professor Andreas Holtermann, National Research Centre for the Working Environment, Lersø Parkalle 105, Copenhagen 2100, Denmark; [email protected]

population. Despite extensive adjustments for potential confounders such as education, father’s origin, lifestyle factors and health-related factors, differences between the OPA groups in socioeconomic status, lifestyle or health may have caused some bias of the results. However, the study has strengths such as extensive adjustments for potential confounders and a validated register-based follow-up, supporting the validity of the findings. The findings on the interplay between OPA and LTPA, and the risk of CHD and all-cause mortality, are in line with recent prospective observational studies reporting a generally increased risk from high OPA and reduced risk from high LTPA on these outcomes,2 termed “The Health Paradox of OPA and LTPA”.3 The adverse effects of OPA on CHD mortality have been shown to be particularly pronounced among workers with low cardiorespiratory fitness.4 Previous studies have shown preventive effects from high LTPA among workers with high OPA.5–7 However, high LTPA has also been observed to increase the risk of CHD among workers with high OPA,8 which has been explained by a potential cardiovascular overload by performing both high OPA and high LTPA.9 In the study by Harari et al,1 men with the combination of moderate-hard OPA and low LTPA did not have a significantly higher risk of CHD and all-cause mortality compared to those with moderate-hard OPA and high LTPA in the fully adjusted statistical model. This finding still leaves the research question of whether workers with high OPA should be recommended to be highly physically active during leisure, unsolved. A recent RCT10 investigated the effects of 1 h per week of aerobic exercise for 4 months offered during working hours on cardiovascular health indicators among cleaners. They observed increased cardiorespiratory fitness, lowered resting and sleeping heart rate, and reduced relative workload (heart rate reserve), but also significantly increased systolic blood pressure. The study10 supports the positive cardiovascular health effects from high LTPA among workers with high OPA reported from cohort studies, but also indicates that high LTPA may cause a

potential cardiovascular overload among workers with high OPA. The contrasting health effects of OPA and LTPA are suggested to be a result of different inherent characteristics of the physical activities during work and leisure. OPA often occurs over several hours on consecutive days and commonly includes activities such as heavy lifting, bending, pushing and pulling, monotonous and static postures with limited ability for pauses and restitution. On the contrary, LTPA commonly occurs over shorter time periods with dynamic movements increasing whole-body metabolism and cardiac output to high intensity levels, with sufficient variation and restitution. The underlying physiological mechanism behind an increased risk of CHD from high OPA could be potential harmful arterial wall stress on the endothelia from long-term high cardiovascular workloads, causing atherosclerosis,11 or sustained elevated blood pressure over the day, or several very high blood pressure peaks from OPA (eg, because of heavy lifting and static postures).12 Future studies ought to include objective field measures of OPA and LTPA for providing more detailed and valid exposure information, including measures of heart rate monitoring and cardiorespiratory fitness for estimating relative workloads. In addition, follow-up studies on physiological measures and harder clinical outcomes should be conducted in order to increase our knowledge about the significance of OPA and LTPA in the aetiology of cardiovascular disease. Such evidence is important for establishing future public and occupational health recommendations, and giving evidence-based advice to workers, enterprises and authorities. Competing interests None declared. Provenance and peer review Commissioned; internally peer reviewed.

To cite Holtermann A. Occup Environ Med 2015;72:615–616. Received 12 March 2015 Revised 24 April 2015 Accepted 25 April 2015 Published Online First 14 May 2015

▸ http://dx.doi.org/10.1136/oemed-2014-102613 Occup Environ Med 2015;72:615–616. doi:10.1136/oemed-2015-102933

Holtermann A. Occup Environ Med September 2015 Vol 72 No 9

615

Downloaded from http://oem.bmj.com/ on April 23, 2017 - Published by group.bmj.com

Commentary REFERENCES 1

2

3

4

616

Harari G, Green M, Selber-Sagi S. Combined association of occupational and leisure-time physical activity with all cause and coronary heart disease mortality among a cohort of men followed-up for 22 years. Occup Environ Med 2015;72: 617–24. Li J, Loerbroks A, Angerer P. Physical activity and risk of cardiovascular disease: what does the new epidemiological evidense show? Curr Opin Cardiol 2013;28:575–83. Holtermann A, Hansen JV, Burr H, et al. The health paradox of occupational and leisure-time physical activity. Br J Sports Med 2012;46:291–5. Holtermann A, Mortensen OS, Burr H, et al. Physical demands at work, physical fitness, and 30-year ischaemic heart disease and all-cause mortality in The Copenhagen Male Study. Scand J Work Environ Health 2010;36:357–65.

5

6

7

8

Holtermann A, Mortensen OS, Burr H, et al. The interplay between physical activity at work and during leisure time—risk of ischemic heart disease and all-cause mortality in middle-aged Caucasian men. Scand J Work Environ Health 2009;35:466–74. Holtermann A, Marott JL, Gyntelberg F, et al. Occupational and leisure time physical activity: risk of all-cause mortality and myocardial infarction in the Copenhagen City Heart Study. A prospective cohort study. BMJ Open 2012;13:e000556. Allesøe K, Holtermann A, Aadahl M, et al. High occupational physical activity and risk of ischaemic heart disease in women: the interplay with physical activity during leisure time. Eur J Prev Cardiol 2014. Published Online First. Clays E, De Bacquer D, Janssens H, et al. The association between leisure time physical activity and coronary heart disease among men

9

10

11

12

with different physical work demands: a prospective cohort study. Eur J Epidemiol 2013;28:241–7. Krause N. Physical activity and cardiovascular mortality —disentangling the roles of work, fitness, and leisure. Scand J Work Environ Health 2010;36:349–55. Korshøj M, Lidegaard M, Skotte J, et al. Does aerobic exercise improve or impair cardiorespiratory fitness and health among cleaners? A cluster randomized controlled trial. Scand J Work Environ Health 2015;41:140–52. Krause N, Brand RJ, Kaplan GA, et al. Occupational physical activity, energy expenditure and 11-year progression of carotid atherosclerosis. Scand J Work Environ Health 2007;33:405–24. Clays E, De Bacquer D, Van Herck K, et al. Occupational and leisure time physical activity in contrasting relation to ambulatory blood pressure. Bmc Public Health. 2012;12:1002.

Holtermann A. Occup Environ Med September 2015 Vol 72 No 9

Downloaded from http://oem.bmj.com/ on April 23, 2017 - Published by group.bmj.com

Occupational and leisure-time physical activity and coronary heart disease Andreas Holtermann Occup Environ Med 2015 72: 615-616 originally published online May 14, 2015

doi: 10.1136/oemed-2015-102933 Updated information and services can be found at: http://oem.bmj.com/content/72/9/615

These include:

References Email alerting service

This article cites 11 articles, 2 of which you can access for free at: http://oem.bmj.com/content/72/9/615#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.

Notes

To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/

Occupational and leisure-time physical activity and coronary heart disease.

Occupational and leisure-time physical activity and coronary heart disease. - PDF Download Free
381KB Sizes 2 Downloads 4 Views