Biology Reference
In-Depth Information
3
2
1
0
10
20
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40
Age (years)
50
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Figure 11.5
Age dependency of social jetlag. Circles represent average values of age
groups (ages 10
has
no entries for social jetlag). Curves are polynomial fits; vertical lines represent standard
errors of the mean (
-
65: 1-year bins;
65: 5-year bins; note that the age group
75
>
SEM; in most cases they are smaller than the respective symbols).
Redrawn after Ref. 2 .
population sleep at least 20% shorter than their weekly average (an estimate
for individual sleep need), that is, lose an entire night every week. An addi-
tional 35% sleep up to 10% shorter on workdays, missing half a night's sleep
every week. Only a quarter of the population gets at least as much sleep on
workdays as their weekly average. Many early chronotypes suffer from sleep
loss on free days (rather than on workdays) for reasons that are not linked to
alarm clocks but to other social constraints. They routinely stay up in the
evenings beyond their circadian bed time due to the social pressure of the
majority of late types in the population. Yet, their circadian clock wakes
them up early in the morning (according to their chronotype). The pressure
to stay up late is even stronger on evenings before work-free days.
The poor health consequences arising from SCRD are summarized in
Table 11.1 (see references for details), and a few examples are highlighted
here. There is a striking association between SCRD and smoking. For
example, independent of social background and region, the number of
smokers in the population increases with the greater the social jetlag. Fur-
ther, the consumption of alcohol and caffeine increases with social jetlag
(T. Roenneberg, unpublished). Based upon the scores from the Beck
Depression Inventory, 16
the tendency toward depression increases when
 
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