KEY POINTS:
Night owls don't just lounge in bed every weekday, they also "catch up" with an extra hour or two at the weekend if they can.
Massey University researcher Sarah-Jane Paine has charted the sleeping habits of 31 Wellingtonians aged 30 to 49.
She divided them into morning and
evening types, based on their answers to an earlier questionnaire completed by more than 2000 people, and put movement recorders on their wrists to measure their sleep at home.
Morning types - those who function best in the morning - slept on average 40 minutes more at the weekend than during the week.
But evening types - night owls who tucked up, and struggled out of bed later - managed an extra hour and 20 minutes' shut-eye at the weekend. Not until 9.10am did they face the world on Saturday and Sunday, compared with 8.20am for the spring-out-of-bed, morning types.
The bigger catch-up for evening types may be due to their having to fit uncomfortably into a day-time schedule of family and work life, said Ms Paine, a doctoral student at Massey's Sleep-Wake Research Centre, which today hosts a seminar in Wellington on sleep research, health services and policy.
"While maintaining an 8-to-5 job, an evening-type person probably still goes to bed later, because physiologically they might not be able to get to sleep any earlier.
"But because of their job they wake earlier than they prefer. Maintaining work means they are cutting short their sleep by maybe one to two hours every day. Therefore at the weekend they need to catch up if they don't need to get up early."
Ms Paine said inadequate sleep had been linked with obesity and diabetes, possibly through the effects of the sleep hormone melatonin on hormones related to appetite.
She will present research to the seminar on disparities in sleep disorders between Maori and non-Maori and the implications for health services.
Research centre director Professor Philippa Gander said the higher rate of the disorders among Maori adults was due to socio-economic differences rather than ethnicity.
Forty Winks
* Evening types: Rely on alarm clock, struggle to wake up, feel best in the afternoon, can stay up late - 25 per cent of adults aged 30 to 49.
* Morning types: Early risers, can do complex tasks or exercise in the morning, have trouble staying up late - 25 per cent.
* Neither type - 50 per cent.
* On average, adults sleep for just under 7 hours each 24 hours.