Editing Jet lag (section)

===Light exposure===
Light is the most powerful external cue–known as Zeitgeber–for synchronizing a person’s circadian rhythm to a new time zone. Timed light exposure can significantly affect a traveler's ability to adapt to a new time zone and reduce jet lag severity. The effectiveness of light as a [[Chronotherapy (treatment scheduling)|chronotherapeutic]] intervention depends on several factors including direction of travel, [[chronotype]], and the traveler's planned activities at the final destination.

Exposure to morning light can help advance an individual’s circadian phase, making it easier for them to fall asleep earlier. This is useful for eastward travel since an individual will gain time in their final destination. Similarly, exposure to evening light can delay the phase, which is beneficial for westward travel since time will be lost at the final destination.

Strict adherence to timing is required for timed light exposure since it can be effective to help people match their circadian rhythms with the expected cycle at their destination.<ref>{{cite journal |last1=Sack |first1=R. L. |last2=Auckley |first2=D. |last3=Auger |first3=R. R. |last4=Carskadon |first4=M. A. |last5=Wright Jr |first5=K. P. |last6=Vitiello |first6=M. V. |last7=Zhdanova |first7=I. V. |year=2007 |title=Circadian Rhythm Sleep Disorders: Part I, Basic Principles, Shift Work and Jet Lag Disorders An American Academy of Sleep Medicine Review |journal=Sleep |volume=30 |issue=11 |pages=1460–83 |doi=10.1093/sleep/30.11.1460 |pmid=18041480 |pmc=2082105}}</ref> [[Light therapy]] is a popular method used by professional athletes to reduce jet lag.<ref>{{cite news |last1 = Mitchell |first1 = Peter |title = LA Dodgers bring secret weapon to Sydney |date=17 March 2014 |url=https://www.smh.com.au/sport/la-dodgers-bring-secret-weapon-to-sydney-20140317-hvjm6.html |website =The Sydney Morning Herald|access-date = 21 October 2014 }}</ref> Timed correctly, the light may contribute to an advance or delay of the circadian phase to match the destination.<ref>{{Cite web |title=The science of jet lag {{!}} Timeshifter® {{!}} Control your circadian rhythms |url=https://www.timeshifter.com/jet-lag/the-science-of-jet-lag |access-date=2025-04-24 |website=Timeshifter® |language=en-US}}</ref> To aid in timing, the [[US Centers for Disease Control and Prevention]] (CDC) recommends [[mobile app]]s which use personalized algorithms to suggest for the correct timing of light exposure and avoidance, when to use [[caffeine]], and when to sleep.<ref>{{Cite web |title=Jet Lag {{!}} CDC Yellow Book 2024 |url=https://wwwnc.cdc.gov/travel/yellowbook/2024/air-land-sea/jet-lag |access-date=2023-01-03 |website=[[CDC]]}}</ref>