Sleep timing of humans can be classified alongside a continuum from early to late sleepers. Morning people or Larks get up early, have an early activity, and go to bed early bed. Evening types or Owls are nocturnal. They get up late, go to bed late and have a good performance in the afternoon, evening or at night. This preference or sleep-wake rhythm changes with age. Although there are some studies addressing this in some countries, here all available data were collated to demonstrate that this trait changes during the lifespan. The new aspect of this cross-sectional approach is that only few studies themselves address the age-related changes of adult lifespan development, but that many studies are available that provide exactly the data needed. The studies came from 27 countries and included 36,939 participants.

Fig. 1. Relationship between age and morning orientation based on the CSM values. Higher values indicate higher morning orientation. People become progressively morning oriented with older age.

The study was based adults and on the Composite Scale of Morningness because this questionnaire can be used to assess preferences for morning or evening hours. It is alos suited to compare different countries. As a result, age was highly significantly correlated with scores on the Composite Scale of Morningness (r=0.70). This relationship seems linear, because a linear regression explained nearly the same amount of variance compared to other models such as logarithmic, quadratic or cubic models. The standard deviation of age correlated with the standard deviation of CSM scores (r=.55), suggesting when there is much variance in age in a study, in turn, there is much variance in morningness. This meta-analytical approach shows that morningness-eveningness changes across the adult lifespan and that older age is related to higher morningness. Older people are on average more morning oriented.

Christoph Randler
PH Heidelberg, Universität Tübingen

Publication

Ontogeny of morningness-eveningness across the adult human lifespan.
Randler C.
Naturwissenschaften. 2016 Feb

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