Less sleep speeds up ageing by 7 years
Sleep deprivation and sleepiness have adverse effects on performance, response time, errors of commission and attention or concentration.
Furthermore, sleep duration has been found to be linked with a wide range of quality of life measures, such as social functioning, mental and physical health and early death, reports the journal Sleep.
"The main result to come out of our study was that adverse changes in sleep duration appear to be associated with poorer cognitive function in later-middle age," said Jane Ferrie, researcher at the University College London Medical School, who led the study.
The researchers also found that, in women, seven hours of sleep per night was associated with the highest score for every cognitive measure, followed closely by six hours of nightly sleep, according to a University College statement.
Among men, the cognitive function was similar for those who reported sleeping six, seven or eight hours; only short and long sleep durations of less than six hours or more than eight hours appeared to be associated with lower scores, according to a University College statement.
The study used data for 5,431 participants (1,459 women and 3,972 men) from Phase 5 (1997-1999) and Phase 7 (2003-2004) of the Whitehall II study, which included more than 10,000 London-based office staff aged 35-55 working in 20 civil service departments in 1985.
Although participants were mostly white-collar workers, the study group covered a wide socio-economic range with a 10-fold difference in salary across the occupational hierarchy.
The authors concluded that adequate, good quality sleep is fundamental to human functioning and well-being.