Every year, twice a year, Daylight Savings Time (daylight savings time) comes around resulting in a one-hour time zone crossing eastward in the spring and westward in the fall. This transition usually results in people complaining about the inconvenience this may cause, and I am sure we can all relate. However, the rationale behind daylight savings time is to create a correspondence between daylight hours and the activity peaks of a population. The time change was actually implemented to benefit us, even though we may not always feel this way.
Credit: Aphiwat Chuangchoem at Stockstop.io
Our Natural Biological Clock: Circadian Rhythm
Interestingly, this transition period not only affects our clocks but also affects our bodies. This happens by disrupting our chronobiologic rhythms, otherwise known as our circadian rhythm. This intrinsic timekeeping system is controlled by natural factors within the body, but also by environmental cues.
How the circadian rhythm works
The normal cycle of light and dark in a day help to keep our bodies on a schedule throughout 24 hours. When light hits our eyes, specifically the retina, signals are transmitted to the suprachiasmatic nucleus (SCN), a structure located within the hypothalamus in our brains. The SCN controls the production of melatonin by the pineal gland, the hormone that helps us sleep. Therefore, when light signals are transmitted to the SCN, the production of melatonin is reduced, and at night when there is less light, the SCN increases melatonin production to make us tired.
With this understanding of our how our sleep cycles work, we see how our circadian rhythm drives wakefulness during the day when stimulated by light to counteract the progressive increase in sleepiness that we experience at night. When our system is properly aligned, we desire to sleep at night and this can help us have a good night’s sleep. Application of light at different times can lead to phase shifts and circadian disorders.
When light is applied at the end of our sleep cycle and early morning, we want to wake up earlier and experience a phase advance. When light is applied in the evening and the earlier periods of the normal sleeping time, the circadian rhythm phase is delayed. By controlling the external cues that influence our circadian system, mostly by light and factors that affect our melatonin production, this can help to properly align our circadian rhythm.
Our circadian rhythm influences health in other ways
Our circadian rhythm not only regulates the sleep and wake cycle, but also affects the daily changes in our body temperature, cortisol, and appetite.[2,4,5] Temporary shifts in the normal circadian rhythm can potentially cause many symptoms. In this article, we review how shifts in sleep cycles can affect your health and the impact on your skin.
Daylight Savings Time Affects Our Sleep
When collectively looking at research studies that have evaluated the effects of daylight savings time on sleep, it can be concluded that an individual’s sleep pattern is often negatively impacted. Your sleep cycle can be altered in a variety of ways. Some examples include:
- You may experience an increase in sleep onset latency. This means it may take you longer to fall asleep which has been attributed to difficulty adjusting to the time change controlled by your internal clock.[6-8]
- You may experience adjustment periods for up to a week. As expected, during the spring you may find yourself wanting to sleep in later because you’ve lost an hour. On the contrary, following the autumn transition period, you may start waking up earlier. Although you may not be impacted at all, it is possible that your sleeping habits may take up to 5-7 days to return to normal. This adjustment can also impact your sleep onset versus wake onset differently, meaning it may be harder for you to fall asleep, or harder for you to wake up.[8-10]
- You may experience fragmented sleep. Your disrupted sleeping pattern may cause you to wake up several times during the night.[2,11,12]10,11
- You may end up sleeping less, and your sleep may be less efficient. After the time change, the amount of time you sleep may be reduced and you may wake not feeling rested. This sleep debt may be even more pronounced for individuals who already experience sleep deficits, making them more vulnerable.[2,8,13]
- You may become less vigilant. In the event that you lose sleep following daylight savings time, you may experience daylight sleepiness and deficits in attention. This can potentially become both a personal and public safety concern, for example in drivers that may result in a car accident.
"Kiefer" (CC BY 2.0) by Rick Camacho
Daylight Savings Time Affects Mood and Concentration
Researchers have shown that the transition period following daylight savings time has been linked to behavior changes. Following the time change in the spring when the clocks move forward, people have reported a decrease in mood. On the other hand, people may experience an improvement in their mood following the autumn transition when they gain an hour of sleep. The enhanced mood people report is likely due to increased wakefulness and alertness following the extra time spent sleeping.
The connection with depression
Interestingly, it is possible that there may be a correlation between depression and daylight savings time, similar to the effect that is appreciated in seasonal affective disorder. One Danish study found that there was an 11% increase in the number of depression cases following the transition period, that eventually dissipated 10 weeks later. The spike in cases of depression could be explained by distress about the earlier advancement of sunset, highlighting the importance of daylight on mood enhancement. Furthermore, the severity of mood disturbance following disruption of the diurnal rhythm can be so extreme it may serve as an explanation for the increase in suicide attempts that are observed following daylight savings time.
In addition, when sleep is disrupted, the lack of restful sleep can decrease alertness and one’s ability to self-regulate. This idea is supported by a study showing that shifts related to daylight savings time led to an increase in non-work related internet surfing, also known as ‘cyberloafing’. Researchers believe the time transition alters the productivity of an individual by inhibiting their counterproductivity and procrastination type behaviors.
One main factor to consider that remains consistent among most studies is that certain populations that are already unstable are likely more vulnerable to the effects of daylight saving time.
Circadian Rhythm and Skin Health
In our bodies, up to 10% of our genes are thought to have circadian control. Some of these genes are involved in the DNA damage repair response, cell division, and cell death. Some of these genes have been identified in cells of the skin, including keratinocytes, melanocytes, and dermal fibroblasts.  There is evidence that UVB radiation can suppress the normal circadian rhythm gene expression within the skin, which could interrupt normal repair mechanisms but the evidence is still early and a connection has yet to be definitely proven.
Role of melatonin in skin health
On the other hand, melatonin, the hormone produced by the brain in the absence of light stimuli has many other important actions such as being an antioxidant, a chemotoxicity reducing agent, and an anti-aging molecule.[22,23]
In the skin, it is suggested that melatonin may have a protective role by several mechanisms. Through its anti-oxidant properties, melatonin may help to prevent against DNA damage induced by oxidative stress from the sun that could cause cancer. Another mechanism by which melatonin protects the skin is through its ability to regulate UV-induced apoptosis or skin damage from the sun. This means that in response to UV stress, melatonin may lead to greater cell survival and thus less photodamage. This idea was supported by Fischer et al. who treated human skin cells with melatonin 30 minutes prior to sun exposure and found these cells to have higher viability than untreated cells. Moreover, cells pretreated with melatonin prior to UV exposure have also been shown to downregulate genes associated with sun damage. 
Does poor sleep lead to lower daytime melatonin levels?
Researchers have looked at how poor sleep can change melatonin levels, especially during the day. The research is still not clear as one clinical study showed that poor sleep may be associated with lower daytime melatonin while another study showed that poor sleep had no effect on daytime melatonin. Therefore, we still do not fully understand how poor sleep affects daytime melatonin.
Disrupted Circadian Rhythms Affects General Health
Disrupted circadian rhythms may contribute to a variety of health problems. Studies have shown that when light is applied in irregular patterns, serum cortisol and temperature measurements were altered which showed how lighting can shift, amplify, or suppress the normal circadian patterns.  This change in normal circadian rhythms cause shifts in eating and sleeping patterns that result in increased postprandial glucose, insulin, and blood pressure, and decreases in leptin levels, which normally helps control our hunger.
The effect of poor sleep on the cortisol hormone
Cortisol is a critical hormone that helps to maintain homeostasis within our bodies. Normally, cortisol peaks in the morning, and slowly tapers throughout the day. When the time changes during daylight savings time, we can experience alterations in our biorhythms that may impair the production of cortisol. In a study analyzing 27,569 lab results over the course of 13-years, researchers found that cortisol increased by approximately 5% for each hour later that the sun rose. Once again, these data reinforce the importance of light in regulating our circadian cortisol rhythms.
Risks to heart and cardiovascular health
Daylight savings time is even associated with an increase in morbidity. Although the results from different studies vary, some have found a correlation between the transition period following daylight savings time and an increase in the incidence of heart attacks.[32,33] Moreover, in the two days following daylight savings time, studies have also shown an associated increase in the number of hospitalizations for ischemic stroke. Although the exact mechanism by which heart attacks and ischemic strokes occur following time changes from daylight savings time are unknown, the peaking incidence of both occurs during the morning hours. This is understandable since circadian misalignment, not specifically studied in relation to daylight savings time, is linked to increased cardiovascular risk, aberrant sleep duration, and increased risk of stroke. [35,36]
Tips for Better Sleep and a Healthier Circadian Rhythm
- Create a set time to go to bed and get up to help maintain your schedule
- Help regulate your circadian cycle through light exposure. By getting natural light during the day, and refraining from exposure to unnatural light sources or blue light in the evening (computer, TV screen, desk lamps) you can help realign your circadian rhythm
- Use blue light reducing apps at night to reduce your blue light exposure from your computer or cell phone
- Exercise regularly to help regulate your circadian rhythm
- Take a nap. If you are experiencing daytime sleepiness that is significantly impairing your ability to function properly, you may benefit from a little shut-eye to help put some pep in your step
- Avoid caffeine. Caffeine can delay your circadian system, and inhibit your drive to sleep. Avoiding or limiting your caffeine consumption to the morning time can help to regulate your sleep cycle