Poor sleep quality greatly increases the risk of high blood pressure in older men, a study has found.
A lack of deep sleep was found to raise the risk by 80% over a period of 3.4 years.
Researchers measured how long 784 men with an average age of 75 spent in "slow wave sleep" (SWS), a deep stage of sleep from which it is difficult to awaken.
Those for whom SWS took up less than 4% of sleep time were significantly more likely to develop high blood pressure, or hypertension.
They also had generally poorer sleep quality as measured by shorter sleep duration, more awakenings at night, and more severe sleep apnoea - a sleep-related breathing problem.
The findings, reported in the American Heart Association journal Hypertension, were not influenced by body weight despite many of the men being overweight or obese.
Obesity is a well-recognised risk factor for high blood pressure.
"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, and that this effect appears to be independent of the influence of breathing pauses during sleep," said Professor Susan Redline at Brigham and Women's Hospital in Boston, US.
Prof Redline also co-led a separate investigation, the Sleep Heart Health Study, which showed that men were likely to have less SWS than women.
The results suggest that poorer sleep in men may partly explain why they are more prone to 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," said Prof Redline.
Slow wave sleep is believed to be important to learning and memory and linked to a range of physiological functions.
Prof Redline pointed out that good quality sleep was the third pillar of health after diet and exercise.
She said: "People should recognise that sleep, diet and physical activity are critical to health, including heart health and optimal blood pressure control. Although the elderly often have poor sleep, our study shows that such a finding is not benign. Poor sleep may be a powerful predictor for adverse health outcomes. Initiatives to improve sleep may provide novel approaches for reducing hypertension burden."
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."