Researchers in Japan found that people with hypertension who slept for less than seven-and-a-half hours were 68 per cent more likely to develop cardiovascular disease (CVD) than those who slept for longer.

What is the research?
Over a four-year period, researchers followed 1,255 people aged 70.4 years on average, who had hypertension.

Assessments were made of sleep length, daytime and night-time BP and cardiovascular events, 99 of which occurred during the study.

They compared the one fifth of patients who slept for the shortest length of time with those who slept for longer, with a cut-off of seven-and-a-half hours.

Short sleep duration was associated with a 68 per cent increased risk of incident CVD, independent of other standard cardiovascular risk factors.

The researchers also looked at whether patients' BP showed a 'riser pattern'. They found that those with a short sleep duration and a mean night-time systolic BP higher than their daytime systolic BP were 4.4 times more likely to develop CVD.

What do the researchers say?
'Shorter duration of sleep is a predictor of incident CVD in elderly individuals with hypertension,' say the researchers, led by Kazuo Eguchi from Jichi Medical University.

They did not find that longer sleep durations were associated with increased CVD risk and noted that people assessed in the study were relatively healthy, rather than ill patients.

'Our study findings may generalise to middle-aged and elderly patients with uncomplicated hypertension.' The researchers conclude: 'Physicians should inquire about sleep duration in the risk assessment of patients with hypertension.'

What do other researchers say?
Professor Jim Horne of the Loughborough University Sleep Research Centre said the findings had been 'overblown'.

'The average age of the patients was about 70, so we do not know what the effect might be for younger people,' he said.

He also pointed out that the researchers had reported an increase in relative, rather than absolute risk. 'There were only about 20 deaths that could be attributable to a lack of sleep.'

tom.moberly@haymarket.com

• Arch Intern Med 2008; 168: 2,225-31

Informing Patients

• Lack of sleep appears to increase risk of cardiovascular disease in elderly Japanese people.
• The findings are based on a small number of events.
• Sleep researchers believe the significance of the findings has been overblown.