Why was this study done?
Most North American adults are physically inactive or sedentary during much of the day. This can lead to a number of poor health outcomes such as unhealthy weight gain, high cholesterol, and cardiometabolic diseases (for example, heart attack and diabetes).
In the body of research looking into workers’ physical activity patterns, most studies have relied on self-reported data from participants. Participants can mistakenly over- or underestimate their activity levels if they are asked to track and report this data themselves. This study was one of very few large-scale studies that monitored daily movement data using an activity tracking device, and that looked at the relationship between activity levels and workers’ cardiometabolic disease risks.
The study also compared younger workers (those aged 40 or younger) with middle-aged and older workers (those older than 40), and men with women, to understand whether differences in cardiometabolic risks exist between those groups. Studies have suggested that as people age, physical activity tends to decline, potentially as they spend more of their time working or on family responsibilities. There is also evidence that physical activity levels differ between men and women, with men typically engaging in more moderate-vigorous activity, and women with more light-moderate activity.
How was the study done?
The study drew on an existing, nationally representative dataset from Statistics Canada’s Canadian Health Measures Survey (CHMS). In this survey, conducted over five cycles between 2007 and 2017, participants were asked to wear an activity tracker (accelerometer) on their right hip during waking hours for seven consecutive days. Survey participants also agreed to have their clinical data collected at testing centres. This data included the following cardiometabolic disease risk markers:
- Waist circumference, where higher numbers may increase cardiometabolic disease risk.
- Systolic and diastolic blood pressure, where higher measures of either type may increase cardiometabolic disease risk.
- Non-high-density-lipoprotein (non-HDL) or “bad” cholesterol level, where high levels may increase cardiometabolic disease risk.
An Institute for Work & Health research team used the activity tracker data to identify six activity patterns and categorize the sample of 8,229 employed participants according to their activity patterns. The team used the clinical data to examine the cardiometabolic disease risk markers of workers in each category.
What did the researchers find?
Drawing on activity tracker data, the team found Canadian workers’ physical activity habits generally fell into one of six patterns. The least active group was used as a baseline to compare cardiometabolic disease risk markers to the other, more active groups.
- The sedentaries (lowest activity; 2,808 workers). This group includes those with the lowest physical activity in their daily work or home lives. These might be, for example, people who commute mostly by car, get up from their desks just to go to the water cooler, and do only light activity such as short walks and household chores in their off-hours. This was the comparison group.
- The steady movers (moderate consistent activity; 3,219 workers). This group has moderate activity levels throughout the day, followed by light activity during the evening hours. They may include workers who are constantly on their feet at work, such as sales associates. They report low levels of physical activity for recreation. This group had lower waist circumference than the lowest activity group.
- The dynamic movers (fluctuating moderate activity; 1,194 workers). This group alternates between light activity and moderate activity throughout the day. They are the second most active group when it comes to recreational activities, though they report low levels of active transportation. This group may include early childhood educators or health-care workers whose workday can be a mix of low activity and bursts of physical movement. This group had lower waist circumference, lower levels of non-HDL cholesterol and lower systolic blood pressure than the lowest activity group.
- The physical workers (high daytime activity; 713 workers). This group engages in vigorous physical activity—activity that makes one sweat and breathe hard—and sustains it throughout most of their daytime hours. Construction workers may be among this group. This group had lower waist circumference and lower non-HDL cholesterol than the lowest activity group.
- The night shifters (moderate evening activity; 225 workers). This group stays moderately active from midday through to midnight. Grocery clerks stocking shelves into the late evening may be among this group. With an average age of 34, workers in this group are the youngest of the six; they are also the ones most active in their commutes. There were no significant differences in the four markers for this group compared to the lowest activity group.
- The exercisers (highest activity; 750 workers). This group spends parts of the workday doing light or moderate activity, but also engages in vigorous physical activity at the start of the day, around noon, and again in the late afternoon and early evening. Members of this group may include office executives with high flexibility and job control. This group has the highest level of recreational physical activity (in both time spent and prevalence). It also has the largest percentage of participants using physically active modes of transportation. Of the six groups, these exercisers have the highest income and tie for the highest level of education. This group had lower levels of waist circumference, non-HDL cholesterol and diastolic blood pressure than the lowest activity group.
No difference in cardiometabolic risk was found between men and women. The only exception was in the highest activity group (the exercisers) where a lower waist circumference was found in women than in men. In terms of age-related differences, in the moderate consistent activity (steady movers) and fluctuating moderate activity (dynamic movers) groups, lower diastolic blood pressure was found in younger workers, but not in middle-aged or older workers.
What are the implications of the study?
Not all patterns of physical activity performed by workers in their daily routines affect their cardiometabolic disease risk the same way. Groups with higher activity levels had greater reductions in cardiometabolic disease risk markers, which supports the idea that maintaining high physical activity levels throughout the day has health benefits. However, groups with moderate physical activity also had lower risk factors. This suggests the value of promoting levels of physical activity that may be more attainable for workers who can’t be more active in their daily lives. The lack of differences between men and women also suggests that similar public health guidance about physical activity can be given to both employed men and women.
What are some strengths and weaknesses of the study?
The strengths of this study include the large and diverse sample of workers pulled from the CHMS surveys, the use of activity tracker data to provide more precise measures of physical activity than self-reports and the use of cardiometabolic health marker data gathered in an objective, clinical setting.
Limitations of this study include the cross-sectional design of the CHMS survey, which is like a snapshot of these workers at a specific moment in time. This design doesn’t provide any information on how the associations found here may change with time. Additionally, activity trackers worn on the hip primarily measure movement of the lower body and may not capture upper body movement, such as carrying heavy loads, that may be common among some workers. Also, there were some factors that may contribute to the results on physical activity and health outcomes that were not collected, such as diet quality, calories burned, and access to exercise equipment or gyms.