Elderly men who spend little time in deep sleep could be at risk of developing high blood pressure, according to US scientists.
A study on 784 patients, in the journal Hypertension, showed those getting the least deep sleep were at 83% greater risk than those getting the most.
Researchers say they would expect a similar effect in women.
The British Heart Foundation said it was important for everyone to prioritise sleep.
High blood pressure - also known as hypertension - increases the risk of heart attack, stroke and other health problems.
Researchers measured the "sleep quality" of 784 men over the age of 65 between 2007 and 2009. At the start none had hypertension, while 243 had the condition by the end of the study.
The patients were split into groups based on the percentage of time asleep spent in deep, or slow wave, sleep. Those in the lowest group - 4% deep sleep - had a 1.83-fold increased risk of hypertension compared with those in the highest group, who spent 17% of the night in deep sleep.
One of the report's authors, Professor Susan Redline from Harvard Medical School, said: "Our study shows for the first time that poor quality sleep, reflected by reduced slow wave sleep, puts individuals at significantly increased risk of developing high blood pressure.
"Although women were not included in this study, it's quite likely that those who have lower levels of slow wave sleep for any number of reasons may also have an increased risk of developing high blood pressure."
The report said further studies were needed to determine if improving sleep could reduce the risk.
Natasha Stewart, senior cardiac nurse at the British Heart Foundation, said: "Whilst this study does suggest a link between lack of sleep and the development of high blood pressure, it only looked at men aged over 65.
"We would need to see more research in other age groups and involving women to confirm this particular association.
"However, we do know more generally that sleep is essential for staying healthy. It's important we all try to make sleep a priority and get our six to eight hours of shut-eye a night."