Decreasing social jetlag with blue light blocking (reducing) glasses

Sleep is a basic human need and essential for good health, quality of life and
performing well during the day. The timing of sleep is regulated by a
homeostatic process (sleep pressure increasing with time awake) and circadian
process. The latter is synchronised (entrained) to the 24-hour light-dark cycle
by light. The relationship between external (social) and internal (biological)
time is called phase of entrainment. People that differ in this trait have
different chronotypes. The distribution of chronotypes is (almost) bell-shaped,
with few extreme chronotypes at both ends. Chronotype is assessed via the
Munich Chronotype Questionnaire (MCTQ; appendix F1b) based on calculating the
mid-point of sleep on free days (MSF) and workdays (MSW), with the MSF being
corrected for sleep deficit accumulated across the workweek (MSF sleep
corrected, MSFsc). Social jetlag is quantified as the difference between MSF
and MSW, and is a marker for circadian rhythm disruption and chronic
physiological stress. The modern 24/7-society ignores that sleep timing is
individual, affecting sleep quality and quantity, leading to sleep deprivation
and directly impacting recuperation and long-term health. About three quarters
of the general population rely on their alarm clocks on workdays, which
especially concerns later chronotypes with early work schedules. From
controlled laboratory studies, there is ample evidence showing the detrimental
effects of sleep deprivation on health and performance, with consequences that
would be catastrophic in real life - especially in e.g. shift-work occupations.
These studies also show that the thresholds for the effects of sleep
deprivation are hard to identify by an individual (6), meaning we need
solutions that provide individuals with ways to better acknowledge their state
of sleep loss.

The American Academy of Sleep Medicine (AASM) defines *inadequate sleep
hygiene* as sleep disruption associated with poor sleep hygiene practices
(AASM, 2010). The International Classification of Sleep Disorders defines
inadequate sleep hygiene as a *sleep disorder due to the performance of daily
living activities that are inconsistent with the maintenance of good quality
sleep and full daytime alertness*. These same sleep hygiene guidelines
recommend sleeping at the same times on every day of the week, hence
irrespective if workday or work-free day. However, we do know that sleep loss
accumulated over the workweek is being compensated by longer sleep episodes on
free days, which is most pronounced in later chronotypes. This phenomenon has
been termed social jetlag, which is positively correlated with smoking and body
mass index (BMI). Therefore, the recommendation to ignore ones* chronotype and
to keep work-schedule fixed sleep times on free days clearly eliminates any
possibility for recovery sleep, which reinforces the increase of chronic sleep
deprivation with to date unknown consequences to society. One solution to this
problem would be to delay sleep on workdays until it matches sleep on free
days, meaning to fully taking account of an individual*s chronotype. Such
strategy would require delaying working hours, an approach of obviously little
success for plenty social reasons and constraints. The alternative solution is
to advance sleep onset on workdays using controlled light exposure, so as to
allow for longer sleep duration and to decrease the workweek daily sleep loss.
We hypothesise that a continuous earlier sleep onset across weeks and months on
workdays will result in an advance of sleep onset also on free days. Previous
studies from our group (GoShort, METC2010/127 and GoLate METc 2011/056) have
shown, for example, the potential of morning light exposure to advance the
circadian phase significantly. In turn, recent studies strongly suggest that it
is both outdoor and artificial blue light in the evenings from primarily TV*s,
LED*s and computer/tablet screens that delay sleep timing, hence resulting in
higher social jetlag. However, no study to date has tested whether shielding
healthy people from short wavelength (blue) light in the evenings is sufficient
to decrease social jetlag and increase sleep quality, applying both subjective
and objective measures. Two recent studies tested blue wavelength light
blocking glasses (worn from 3 hours before bedtime) to treat patients with
insomnia and showed significant improvements in sleep quality. However,
although the numbers of participants in these studies were small with about
only 20 participants in total, the authors did find a non-significant trend
towards an advance in sleep timing. Therefore, we here adapt this simple
protocol and study more individual to increase statistical power and we will
add objective sleep timing measures (actigraphy). We aim to assess the effect
of shielding participants form blue light exposure when they are indoors to
push the circadian clock towards the social one. This study will give important
insights into the effectiveness of home-based interventions to decrease social
jetlag/chronic sleep deprivation.

To elucidate the changes in the timing of sleep and waking, sleep quality and
endogenous circadian phase in different chronotypes (e.g. *owls* vs. *larks*)
with different amounts of social jetlag shielded from short wavelength (blue)
light in the evenings using short wavelength (blue) light blocking (reducing)
orange glasses (experimental condition) compared with amber glasses
(placebo/control).

This longitudinal and interventional field study entitled *Decreasing social
jetlag with light* is an integrated project in the research consortium *OnTime
- How to fix a (broken) circadian clock* funded by STW Perspectief 2010 program
(project number P10-18). In a matched design placebo controlled trial we will
equip 81 participants (with a social jetlag of at least 2 hours) with short
wavelength (blue) light blocking (reducing) orange glasses to be worn in the
evenings for 16 days. In a sex-age-social jetlag matched control group (81
participants), the same paradigm will be used but participants will instead be
equipped with amber glasses (blocking (reducing) ultraviolet light, blue and
longer wavelengths being transmitted). When waking up during the night, e.g. to
use the toilet, participants will be asked to also put on the glasses before
switching on the room lights. These filters are approved in previous studies
and do not interfere in any way with the visual comfort of watching TV or
working at a computer screen. Our workgroup has experience with applying
similar applications in human studies (METc2007/129). Effects will be measured
by comparing the intervention period with a 14-day baseline period. In two
recent studies participants were asked to wear similar glasses from 3 hours
before bedtime. We here base our study on chronotype, meaning that each
participant will wear the glasses from 8 hours before mid-sleep (MSFsc,
chronotype, as assessed by the Munich Chronotype Questionnaire at before the
study) until actual sleep time (lights out), and hence defined individually for
each participant. Each participant will be informed via SMS about when to put
on the glasses. During four evenings (hourly) separated by each one week,
participants will collect saliva.

For 16 consecutive days from 8 hours before mid-sleep (MSFsc, chronotype, as
assessed by the Munich Chronotype Questionnaire before the study) until actual
sleep time (lights out) participants will wear either of the two *special*
glasses (see point 6.1 below). Each participant will be informed via SMS about
when to put on the glasses. When waking up during the night, e.g. to use the
toilet, participants will be asked to put on the glasses before switching on
the room lights. These filters are approved in previous studies and do not
interfere in any way with the visual comfort of watching TV or working at a
computer screen. Our workgroup has experience with applying similar filters in
human studies (METc2007/129).

There are no known or expected adverse events from participating in our study.
The only intervention is to wear orange/amber glasses in the evening and to
complete questionnaires. We do not apply any severe or acute sleep deprivation
protocol. All participants will have at all days the possibility to sleep at
home without interfering with their normal daily routines.