November 10 (HealthDay News) -- Getting less than 7.5 hours of sleep a night may increase the risk of heart disease in elderly people with high blood pressure, say Japanese researchers.

They tracked the sleep of 1,255 people, average age 70.4 years, and followed their health for about 50 months. During the follow-up, there were 99 cardiovascular disease events such as stroke, heart attack and sudden cardiac death.

People who slept less than 7.5 hours a night had the highest risk, the team reports in the Nov. 10 issue of the Archives of Internal Medicine.

"The incidence of cardiovascular disease was 2.4 per 100 person-years in subjects with less than 7.5 hours of sleep and 1.8 per 100 person-years in subjects with longer sleep duration," wrote Dr. Kazuo Eguchi, of Jichi Medical University in Tochigi, and colleagues.

They also found that participants with shorter sleep duration plus an overnight increase in blood pressure had a higher incidence of heart disease than those who slept longer and had no overnight increase in blood pressure. However, the incidence of cardiovascular disease in patients who had more sleep compared to those who had less sleep was similar in those who didn't experience an overnight increase in blood pressure.

"In conclusion, shorter duration of sleep is a predictor of incident cardiovascular disease in elderly individuals with hypertension," particularly when it occurs with elevated night-time blood pressure, the researchers concluded. "Physicians should inquire about sleep duration in the risk assessment of patients with hypertension."

"Reflecting changing lifestyles, people are getting less sleep in modern societies," they added. Adequate sleep is essential for preventing health problems such as obesity and diabetes, as well as several risk factors for cardiovascular disease, they said.

SOURCE: JAMA/Archives journals, news release, Nov. 10, 2008