Low job control linked to hypertension among male workers: study

Low job control is a significant factor in the development of hypertension among workers, according to new research conducted by the Institute for Work and Health (IWH) and the Institute for Clinical Evaluative Sciences (ICES).

The study, published in the Canadian Journal of Public Health, found that over a nine-year period, 27 per cent of men in occupations with low job control were diagnosed with hypertension, compared with 18 per cent of men who report higher degrees of job control. The same connection was not apparent among women workers.

Job control refers to the ability to make decisions about how work is done or skills are used to meet the demands of the job.

While previous studies have pointed to the causal relationship between work characteristics and the development of cardiovascular disease, this is the first study in Canada to look at the relationship, says Cameron A. Mustard, IWH president and senior scientist.

“It is novel, too, in its estimate of the risk of progressing to hypertension that is associated with characteristics of people’s psychosocial working environment,” says Mustard, who co-authored the study with IWH scientists Peter Smith, Hong Lu and Richard Glazier.

“And in this study, the particular attribute that was identified as being a risk factor for men was low job control,” Mustard said.

The study found 12 per cent of hypertension cases among men can be directly attributed to low job control. Thus, apart from obesity (which is linked to 26 per cent of hypertension cases among men), hypertension is more likely to be caused by low job control than by those behavioural factors usually associated with hypertension — smoking, drinking, low physical activity and low daily consumption of fruits and vegetables.

Smith, the IWH scientist who led the research, says the study suggests that attempts to reduce hypertension should include an assessment of ways to modify work environments.

Mustard agrees, saying the researchers are not diminishing the importance of public health efforts to focus on the health benefits of physical activity, not smoking and moderate alcohol consumption.

“But in this study, [we’re looking at] a relatively invisible characteristic — invisible in that we don’t think of the way in which our work is organized as a risk factor for cardiovascular disease,” he says.

“Our proposition is, maybe it should be more visible because it’s at least as important in this study as smoking, physical activity and alcohol consumption.”

However, while low job control appears to be an important risk factor in the development of hypertension, Mustard notes, it’s hard to know how to minimize the risk. No solid evidence yet exists to show exactly how jobs can best be modified to provide workers with more job control.

“We also don’t know yet — even if we can design work so that more people at work have more control — whether that would actually protect people from progressing to hypertension,” he says.

During the study period, 19 per cent of all participants developed hypertension. Among these, the incidence for men was 21 per cent; and for women, 18 per cent. After taking into account a range of personal and work factors that could affect the incidence of hypertension, men with the lowest levels of job control still had a significantly increased risk of developing hypertension than men with the highest levels of job control (i.e., 27 per cent versus 18 per cent, which represents an 85 per cent increase in risk among men with low job control).

Mustard says women may not have shown the same profile of risk because of physical differences.

“It leads us to ask questions about the way in which the biology of men and women may differ when they’re in social experiences that involve perceptions of control,” he says.

Hypertension, or high blood pressure, is an important indicator of the development of cardiovascular disease. It is a risk factor for strokes and heart attacks. In Ontario, the incidence of hypertension increased by 60 per cent during the decade between 1995 and 2005 — from 153 to 244 cases per 1,000 Ontarians.

The study, funded by the Canadian Institutes of Health Research, followed 6,611 workers aged 35 to 60 in Ontario who had not been previously diagnosed with hypertension. These workers were drawn from the 2000–01 Canadian Community Health Survey (CCHS), which provided information on their health behaviours, their psychosocial work environment (including job control) and other work and personal factors. The information was then linked to the Ontario Health Insurance Plan (OHIP) database for physician services and the Canadian Institute for Health Information Discharge Abstract Database (CIHI-DAD) for hospital admissions up to March 2010. This allowed researchers to detect new diagnoses of hypertension among the group for a nine-year period.

The study is available in the January/February 2013 issue of the Canadian Journal of Public Health.