Long hours spent working will do no favors for your blood pressure, a new Canadian study suggests.

The five-year study tracked the working hours and blood pressure readings of 3,500 white-collar workers at three public institutions in the province of Quebec.

Compared to those who worked less than 35 hours a week, those who worked 49 or more hours each week had a 70% higher risk of what’s known as “masked” hypertension — high blood pressure that can be missed during a routine medical appointment, but is detected when blood pressure is tracked at home.

Lots of overtime was also tied to a 66% higher risk of “sustained” hypertension — high blood pressure that’s recorded both in and out of healthcare settings.

The study couldn’t prove cause-and-effect, but even a few extra working hours per week seemed to matter to heart health. For example, people who worked between 41 and 48 hours a week had a 54% higher risk of masked hypertension and a 42% higher risk of sustained hypertension, the researchers reported Dec. 19 in the journal Hypertension.

The exact connection between overtime and higher blood pressure isn’t clear, said lead author Xavier Trudel.

“The link between long working hours and high blood pressure in the study was about the same for men as for women,” noted Trudel. He’s an assistant professor in the department of social and preventive medicine at Laval University in Quebec City.

In their calculations, Trudel’s team took into account factors such as age, type of work and whether the person smoked or was obese.

The study also accounted for “job strain,” Trudel said in a journal news release. Job strain was defined as “a combination of high work demands and low decision-making authority,” he said.

“Future research could examine whether family responsibilities — such as a worker’s number of children, household duties and child care role — might interact with work circumstances to explain high blood pressure,” said Trudel.

Overall, 19% of the workers had sustained hypertension, including those who were already taking high blood pressure medications. More than 13% of the workers had masked hypertension and were not being treated for high blood pressure.

The researchers stressed that the new study only included white-collar workers, so the findings “may not reflect the impact on blood pressure of shift work or positions with higher physical demands.”

The bottom line, according to Trudel, is that “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.

Two experts in heart health agreed with that advice.

The new findings “add to our knowledge base regarding the impact of excess work and lifestyle stressors on our health,” said Dr. Benjamin Hirsh. He directs preventive cardiology at the Northwell Health Sandra Atlas Bass Heart Hospital in Manhasset, N.Y.

“Masked” hypertension, especially, can be a silent killer, Hirsh said, but it can be easily diagnosed by the use of a wearable blood pressure cuff at home.

Dr. Satjit Bhusri is a cardiologist at Lenox Hill Hospital in New York City. He said the new study shows that masked hypertension, “if untreated and not recognized, puts patients at an elevated risk of heart attacks and strokes.” For that reason, “it is important to get an accurate social and work history from our patients,” he said.

According to the study authors, nearly half of Americans aged 18 and older have high blood pressure, which is a major factor in more than 82,000 deaths per year. About 15 to 30% of U.S. adults have masked hypertension.

More information

The U.S. National Heart, Lung, and Blood Institute has more on high blood pressure.