Abstract: | Chronotype is an established concept designed to identify distinct phase
relationships between the expression of circadian rhythms and external synchronizers
in humans. Although it has been widely accepted that chronotype is subjected to
ontogenetic modulation, there is no consensus on the interaction between age and
gender. This study aimed to determine the relationship between age- and
gender-related changes in the morningness-eveningness character in a large sample of
people. A total of 14,650 volunteers were asked to complete the Brazilian version of
the Horne and Östberg chronotype questionnaire. The data demonstrated that, on
average, women were more morning-oriented than men until the age of 30 and there were
no significant differences between men and women from 30 to 45 years of age. In
contrast to the situation observed until the age of 30, women older than 45 years
were more evening-oriented than men. These results suggest that the ontogenetic
development of the circadian timekeeping system is more plastic in men, as
represented by the larger amplitude of chronotype changes throughout their aging
process. The phase delay of adolescence and phase advance of the elderly seem to be
phenomena that are more markedly present in men than in women. Thus, our data, for
the first time, provide support that sharply opposes the view that there is a single
path toward morningness as a function of age, regardless of gender. |