Leisure time physical activity and physical activity performed at work have opposite associations with cardiovascular health and mortality, according to results of an observational study in more than 100,000 individuals.
It found that higher leisure time physical activity was associated with reduced major adverse cardiovascular events (MACE) and all-cause mortality risk, whereas higher occupational physical activity was associated with increased risks, independent of each other.
“This is the biggest study to date where we have seen consistent findings when we adjust for lifestyle factors, health factors, living conditions, and socioeconomic status and, in the subgroup analyses, we find the same association in each and every group,” Andreas Holtermann, a professor at the National Research Centre for the Working Environment in Copenhagen, Denmark, said in an interview.
The findings, he said, support what the researchers previously termed, the “physical activity paradox.” The team also found an 18% increased risk of all-cause mortality among men, but not women, with high work activity in a recent systematic review. A separate study from Norway also showed a U-shaped relationship between occupational physical activity and mortality.
“What we see in a lot of these occupational patient groups is that they don’t get their heart rate up during work,” Holtermann said. “Their heart rate is low to moderate, and they never get up to sufficient high levels to promote their cardiorespiratory fitness.”
Leisure time physical activities also typically comprise dynamic activities of higher intensity and shorter durations, while workers typically engage in more static, lower-intensity movements over 7 or 8 hours each workday. “There’s a massive difference in duration,” as well as little opportunity to tailor or adapt the work activity to levels of fatigue or pain, he said.
The concept that certain activities at work can be harmful isn’t new, but studies comparing physical and occupational activities are limited, data quality is often poor, and “always there’s this debate about is it just about socioeconomic confounding or is it really a causal relationship?” Holtermann said. “You can never say there’s no confounding whatsoever, but at least this is one of the studies where we’ve been able to take into account as much as possible.”
The current study included 104,046 individuals, aged 20 to 100 years, in the Copenhagen General Population Study who had baseline measurements in the years 2003 to 2014 and were linked to national Danish patient and death registries.
Questionnaires on leisure and occupational physical activity were used to categorize participants as low, moderate, high, and very high activity for both activities. Cox regression models were adjusted for 20 potential confounders including socioeconomic factors such as cohabitation, marital status, education, and household income.
During a median follow-up of 10 years, there were 7913 (7.6%) MACE (fatal and nonfatal myocardial infarction, fatal and nonfatal stroke, and other coronary death) and 9846 (9.5%) deaths from all causes.
Compared with low leisure time physical activity, the adjusted risk of MACE was reduced 14%, 23%, and 15% with moderate, high, and very high levels of activity, respectively. Compared with low occupational activity, the adjusted MACE risk was increased 15% and 35% with high and very high levels of occupational activity, respectively.
The risk of all-cause mortality followed a similar pattern. Compared with low leisure activity, moderate, high, and very high levels of leisure activity were associated with 26%, 41%, and 40% reduced risks of all-cause death, respectively. High and very high levels of work activity, however, were associated with 13% and 27% increased risks of death, respectively, compared with low work activity.
Sensitivity analyses showed similar associations for both leisure time and occupational physical activity with risk of both outcomes, according to the study, published this week in the European Heart Journal.
“It’s important to tell those doing manual work that they don’t get healthier and fit from the activities they’re doing during work, so it’s important they’re being physically active during their leisure time to promote health,” Holtermann said. “But workplaces should also be aware of this because, in the end, the sustainable solution is not only to tell those lower socioeconomic, manual workers they should just do exercise at leisure…but to make the activity at work healthy.”
Scandinavian companies have been offering fitness enhancing activities at work for years, with the Copenhagen municipality taking it a step further and making 1 hour of physical activity per week mandatory for those working in the eldercare sector, he noted. The need to promote longevity among lower socioeconomic, manual workers has taken on even greater urgency, however, as Denmark looks to increase its retirement age from 67 to 72 years.
Further investigation of the association between occupational physical activity and health was also recently encouraged by the World Health Organization guidelines on physical activity and sedentary behavior, Holtermann said.
In an interview, Richard Josephson, MD, director of the Cardiovascular and Pulmonary Rehabilitation Center at University Hospitals in Cleveland, Ohio, said “the intriguing and novel finding here is that they found an adverse gradient with occupational work and health outcomes. The data on that in studies around the world are mixed.”
“I, for one, would be a bit skeptical of over-analyzing the occupational data because it’s not very strong for a variety of reasons — it’s recall bias, it’s self-reporting, it’s only divided into four tiers, and only a fraction of the patients were actually answering the question,” said Josephson, who also is a professor of medicine at Case Western Reserve University School of Medicine.
He agreed that physical activities performed at leisure and work are different in nature, but said one also has to take into account workplace factors such as stress or toxins. “If your job was to be a caddy on a golf course, I would think that working more is better than working less, but if you’re working in a coal mine, I would think working more is worse than working less.”
It’s unlikely a randomized trial will take place to evaluate the health effects of occupational vs leisure activities or whether the association between the two activities is independent, as the researchers suggest.
That said, “the data from this study shows that whatever level of physical activity you’re doing at your job, it is still important to maintain physical activity in your leisure activities,” Josephson said. “You shouldn’t come home from the factory and say: I was just working all day and there’s no need for me take a walk outside, there’s no need for me to play sports on the weekend.”
In an accompanying editorial, Martin Halle, MD, and Melanie Heitkamp, PhD, both of the Technical University of Munich, Germany, reiterate many of the same limitations. Nonetheless, the large cohort and methodological strengths of the Copenhagen General Population study “make an important and significant contribution to the cardiovascular and overall risk of occupational work, which has to be followed and differentiated in future studies.”
They also call on companies to offer breaks and recovery time during work, sufficient recreational breaks, and complementary exercise training for their employees, especially for workers in heavy manual jobs.
For their part, healthcare professionals should “assess and address the particularly elevated risk of heavy work occupations and emphasize a healthy lifestyle in these high-risk patients at an early stage,” Halle and Heitkamp write.
The study was supported by the Capital Region of Copenhagen, the Danish Heart Foundation, the Danish Lung Association, Velux Foundation, and Lundbeck Foundation. The authors, Josephson, and the editorialists have disclosed no relevant financial relationships.