Past studies have found that home monitoring may aid blood pressure control, with a 2010 review of 37 clinical trials finding that, overall, people who used monitors shaved a few extra points from their blood pressure. They were also more likely to cut down on medication.

The new study, which appeared in the Canadian Medical Association Journal, focused on patients who'd recently had a stroke - a group that hasn't really been studied when it comes to home blood pressure monitoring.

Overall, home monitoring did not improve blood pressure control in patients with hypertension and a history of stroke, wrote lead researcher Sally Kerry, a researcher at Queen Mary, University of London.

The exception, though, was patients whose blood pressure was poorly controlled at the study's start, meaning it was above the standard high blood pressure cutoff of 140/90 mm Hg.

In that case, patients given a home monitor cut an average of 11 points from their systolic blood pressure - the top number in the reading. That compared with just under five points among patients who were not given the devices.

Kerry's team randomly assigned the patients to either stick with standard care only or get a home monitor, along with instructions on how to use it and periodic phone calls from a nurse to check on how they were doing.

Over the next year, the results were mixed. Among the patients who didn't seem to benefit were those who'd been left disabled by their stroke, while non-disabled patients cut about four points.

Some patients had difficulty carrying out monitoring because they did not have a carer who lived with them to help, said Kerry.

Many people with high blood pressure already have home monitors, and these findings don't mean that stroke survivors can't benefit, although a person left disabled by a stroke may be not the best candidate, said Hayden Bosworth, a professor of medicine at Duke University, who was not part of the study.