A study has found that US citizens who are older and are experiencing mental health issues or depression are less likely to sleep for the minimum seven hours that is recommended or more.
The link between sleep disorders and factors such as race, marital status, educational background and income were also explored in the research that was presented at Sleep 2009, the 23rd annual meeting of the Associated Professional Sleep Societies, yesterday (June 10th).
Lead author Dr Karen Rose, from the University of Virginia in Charlottesville, commented: "We were surprised by the fact that the self-reported amount of physical activity did not predict functional outcomes of sleep.
"We anticipated that people who reported lower levels of physical activity would have more difficulty with sleep-related functional outcomes."
She added that the number of hours sleep an individual managed to get did not necessarily determine whether their functional behaviour would be impaired by feelings of tiredness.
Researchers at the California Pacific Medical Center in San Francisco have identified a link between sleep disorders and a greater vulnerability to sudden death.