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 80pc 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 4pc 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.