Her team studied more than 8,000 people, aged 35 to 55, who were followed for a number of years.

Among participants who slept six, seven or eight hours a night at the start of the study, a decrease in nightly sleep duration was associated with a 110 percent excess risk of cardiovascular-related death.

Similarly, among those who slept seven or eight hours per night at the start of the study, an increase in nightly sleep duration was associated with a 110 percent excess risk of non-cardiovascular death.

The study appears in the Dec. 1 issue of Sleep.

On average, most adults need seven to eight hours of sleep per night to feel well-rested and alert, according to the American Academy of Sleep Medicine.

The study found that people with high diastolic blood pressure, which is the bottom number of a blood pressure reading, were more likely to have cognitive impairment, or problems with their memory and thinking skills, than people with normal diastolic readings.

For every 10 point increase in the reading, a person?s risk for cognitive problems was 7 percent higher. The results were adjusting for other factors that could affect cognitive abilities like age, smoking status, exercise level, education, diabetes, or high cholesterol.

The study involved nearly 20,000 people 45 and older across the country that participated in the Reasons for Geographic and Racial Differences in Stroke Study and had never had a stroke or mini-stroke. A total of 1,505 of the participants, or 7.6 percent, had cognitive problems, and 9,844, or 49.6 percent, were taking medication for high blood pressure.

“It’s possible that by preventing or treating high blood pressure, we could potentially prevent cognitive impairment, which can be a precursor to dementia,” said Dr. Georgios Tsivgoulis of the University of Alabama at Birmingham, one of the study authors.

Newsmax.com Health Alerts 10/25/09