New York, Dec 19 (IANS): People who spend long hours at the workplace are more likely to have high blood pressure -- including a type that can go undetected during a routine medical appointment, researchers warned on Thursday.

Compared with colleagues who worked fewer than 35 hours a week, working 49 or more hours each week was linked to a 70 per cent greater likelihood of having "masked" hypertension and 66 per cent greater likelihood of having sustained hypertension -- elevated blood pressure readings, according to the study published in the American Heart Association's journal Hypertension.

The findings was true for both men and women staffers and accounted for variables such as job strain, age, sex, education level, occupation, smoking status, body mass index (BMI) and other health factors.

"Both masked and sustained high blood pressure are linked to higher cardiovascular disease risk," said lead study author Xavier Trudel, assistant professor in the social and preventive medicine department at Laval University in Quebec, Canada.

The new study, conducted by a Canadian research team, enlisted more than 3,500 white-collar employees at three public institutions in Quebec.

These institutions generally provide insurance services to the general population.

"The observed associations accounted for job strain, a work stressor defined as a combination of high work demands and low decision-making authority. However, other related stressors might have an impact," Trudel said.

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, the authors wrote.

The five-year study involved three waves of testing -- in years one, three and five.

In all, almost 19 per cent of the workers had sustained hypertension, which included employees who were already taking high blood pressure medications. More than 13 per cent of the workers had masked hypertension and 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 noted.

The study "did not include blue-collar workers (employees who are paid by the hour and perform manual labor work in positions such agriculture, manufacturing, construction, mining, maintenance or hospitality service).

Therefore, these findings may not reflect the impact on blood pressure of shift-work or positions with higher physical demands," the authors said.

Other limitations include the study's measurement of blood pressure 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 emphasised.

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.