Quantitative Analysis of Human Chronotypes

Like most other organisms, human behaviour is under control of a
circadian (= about a day) clock which can adapt to the daily change
of light and darkness. The capability of the circadian clock to
synchronize to the light-dark cycle is highly systematic and under
genetic control. Daily behaviour of humans can vary greatly,
leading to different chronotypes and extreme chronotypes are
commonly described as 'owls and larks'. While larks fall asleep in
the early evening and wake up early in the morning, owls go to bed
when larks wake up, sleeping until about noon. Recently, the Munich
ChronoType Questionnaire (MCTQ) has been developed in order to
quantitatively assess chronotype and to face problems arising from
common work day schedules. Chronotypes are normally distributed in
the general population. MSF-Sc, the middle of sleep phase on free
days corrected for sleep dept accumulated on work days, is used as
reference point for chronotype. The objectives of this study were
both to validate and improve the MCTQ and to identify and estimate
biological and social factors that potentially influence the
distribution of chronotypes. Test-retest reliability was controlled
at an interval of six months (n=101). Both dates show a highly
significant correlation (p0.027, Bonferoni corrected level of
significance: p=0.0012). Test-retest reliability was controlled
separately for females and males, different age (≤30 years and
>30 years), and chronotype groups (MSF-Sc ≤4.28 and >4.28). A
sample of 15 people was tested at an interval of three weeks. The
results of both dates correlate with high significance (p0.05, Bonferoni corrected level of significance:
p=0.002). The capability of the MCTQ to assess actual sleep times
was tested with 6-week long sleep logs (n=628). Again, gender, age,
and chronotype groups were evaluated separately and chronotypes
were separated into five different groups (MSF-Sc