Overworked employees are more likely to have high blood pressure, including a type that goes undetected in routine tests, according to a study published on Thursday. The study, published in the journal Hypertension, enlisted more than 3,500 white-collar employees at three insurance services providing institutions in Quebec, Canada.
According to the researchers from Laval University in Canada, working 49 or more hours each week was linked to a 70 per cent greater likelihood of having masked hypertension compared to those who worked fewer than 35 hours a week.
In masked hypertension, the study noted, high blood pressure readings are normal during routine health care visits, but elevated when measured elsewhere. They added that there was a 66 per cent greater risk of elevated blood pressure readings in those who worked nearly 50 hours a week, compared to colleagues whose weekly work period was less than 35 hours.
The scientists also said working between 41 and 48 hours each week was linked to a 54 per cent greater chance of having masked hypertension, and 42 per cent greater likelihood of having conventional high blood pressure.
"Both masked and sustained high blood pressure are linked to higher cardiovascular disease risk," said lead study lead author Xavier Trudel from Laval University.
Accounting for other factors such as job strain -- a work stressor defined as a combination of high work demands and low decision-making authority -- Trudel said such related stressors might also have an impact on hypertension.
"Future research could examine whether family responsibilities - such as a worker's number of children, household duties and childcare role - might interact with work circumstances to explain high blood pressure," Trudel explained.
Three waves of testing were part of the five-year study, with assessments carried out in the first, third and fifth years. In-clinic blood pressure readings were measured with a wearable monitor to check each participant's resting blood pressure three times in one morning.
For the rest of the workday, the researchers said, the participants wore the blood pressure monitoring device, which took readings every 15 minutes -- collecting a minimum of 20 additional measures for a single day.
They said, almost a fifth of the workers had high blood pressure, which included employees who were already taking high blood pressure medications. More than 13 per cent of the workers had masked hypertension, and were not receiving treatment for high blood pressure.
"The link between long working hours and high blood pressure in the study was about the same for men as for women," Trudel said.
Limitations of the study, the researchers said, included not assessing blue-collar workers, who are paid by the hour and perform manual work in positions such as agriculture, manufacturing, construction, mining, maintenance or hospitality service.
Therefore, they added, these findings may not reflect the impact on blood pressure of shift-work or positions with higher physical demands. Also, the study's blood pressure measurement was carried out only during daytime hours, and the omission of hours worked outside participants' primary job.
"People should be aware that long work hours might affect their heart health, and if they're working long hours, they should ask their doctors about checking their blood pressure over time with a wearable monitor," Trudel said.
"Masked hypertension can affect someone for a long period of time and is associated, in the long term, with an increased risk of developing cardiovascular disease. We have previously shown that over five years, about 1 out of 5 people with masked hypertension never showed high blood pressure in a clinical setting, potentially delaying diagnosis and treatment," he added.