Shakespeare described sleep as knitting up the “raveled sleeve of care.”

According to a UVA study, most elderly people aren’t getting enough knitting.

A survey of 1,570 men and women who were 60 years of age or older indicated that 55 percent slept an average of seven hours or less each night during the month before the study (eight hours is recommended).

Short sleep duration is a serious concern for older adults, the study said, as it has been associated with cardiovascular disease, insulin resistance and other health issues.

UVA researcher Karen Rose, the study’s lead author, said some results were surprising, such as physical activity not playing a role in amount of sleep.

“We anticipated that people who reported lower levels of physical activity would have more difficulty with sleep-related functional outcomes,” Rose said. Another surprise was that the amount of sleep did not predict how well a person functioned.

In fact, according to a separate study conducted at the University of California, San Diego, seniors’ cognitive performance is generally less affected by sleep deprivation than younger adults.

Older participants (ages 59 to 82) out performed a younger group (ages 19 to 38) on a variety of tests, including measures of working memory, selective attention/inhibition and verbal encoding and retrieval after sleep deprivation.