Not getting enough sleep could increase a person's risk of developing high blood pressure, said US researchers who monitored over 500 middle aged people for 5 years. They hope that the discovery of this new risk factor will help prevent more people developing high blood pressure and suggest more research is done to see if improving sleep patterns reduces the risk.

The study was the work of lead author Dr Kristen L Knutson of the University of Chicago, and colleagues, and is published in the 8 June issue of the Archives of Internal Medicine.

High blood pressure accounts for 7 million deaths worldwide and affects about one third of Americans, wrote the authors in their background information.

Researchers already know of a possible link between self-reported hours of sleep and high blood pressure but this appears to be the first study to look at both cross-sectional (taking a snapshop of a group of people showing different patterns of the same variables) and longitudinal (following a group of people over time) measurements of sleep and blood pressure.

The study was part of a larger investigation called Coronary Artery Risk Development in Young Adults (CARDIA) which took blood pressure measurements in 2000 and 2001 and in 2005 and 2006. For this study, the participants were 578 African Americans and whites aged from 33 to 45 years at the start.

Sleep was also measured using a sensor worn on the wrist that measures movement patterns characteristic of sleep and wakefulness (actigraphy). The sensor was worn on three consecutive days between 2003 and 2005 and gave measures of sleep duration and sleep maintenance (a measure of sleep quality).

The results showed that on average, participants slept for about 6 hours a night and only 1 per cent averaged 8 or more hours a night.

After excluding those participants who were on blood pressure medication, and adjusting for age, race and sex, the results also showed that: Participants who had less sleep and lower quality sleep were significantly more likely to have higher systolic and diastolic blood pressure readings (ie from the cross-sectional point of view less and poorer sleep predicted higher blood pressure across the group).
Less and lower quality sleep was also significantly more likely to be linked to adverse changes in systolic and diastolic blood pressure over a 5 year period (ie from the longitudinal view the lower sleep figures predicted the increases in blood pressure figures over time, all P