As the vast body of evidence linking sleep quality and circadian rhythms to physical health, cognitive performance and mental well-being continues to grow, many scientists and health care professionals are casting an inquiring eye on Daylight Savings time. There’s far more than just an hour of sleep at play with this time shift. Of course, in this chronically sleep deprived era, that hour shouldn’t be considered an inconsequential springtime loss. However, it is also the artificial extension of daylight hours into the evening that may make Daylight Saving Time bad for your health.

Sleep Quality Essential to Health

Daylight Saving Time is disruptive to sleep. Sleep quality, meaning a sufficient amount and quality that allows you to successfully move through all of the sleep stages, impacts physical and cognitive health in a number of ways. Disruption of sleep, including not sleeping enough, can have far-reaching negative short-term and long-term effects on health and well-being. Short-term effects include decreased cognitive performance, particularly in the realms of memory and learning, an increased risk of mood and emotional disorders and a higher risk of workplace injuries and traffic accidents. Long-term impacts include an increased risk of some cancers, obesity, type two diabetes, clinical depression and cardiovascular disease.

Distinct Impact Patterns Suggest Daylight Saving Time Bad for Many

Depending on the person, it can typically take between three days and a week to adjust to the Daylight Saving Time shift. However, not everybody is typical. It can take some people significantly longer to adapt, with some never fully adapting to the time shift. For those with a chronic health condition that can be a hard, even dangerous adjustment period. Cardiac incident patterns offer a clear example of that.

Numerous studies point to a distinct pattern of adverse cardiac events associated with Daylight Saving Time. The number of heart attacks and strokes typically increases in the days immediately following the time shift. Interestingly, a 2014 study published in Open Heart found that the number of heart attacks on the Monday after Daylight Saving Time began increased by 25 percent, then on the Tuesday after the return of Standard Time in the fall, decreased by 21 percent.

The time shifts into and out of Daylight Saving Time are associated with higher numbers of strokes during the few days after the change, as well as other conditions that impact stroke risk. These include high blood pressure and, in the autumn, with the return to Standard Time and an abrupt loss of evening light, an increased risk of depression.

It’s Much Bigger Than an Hour

That abrupt loss of evening light is a much bigger deal that it may seem at first glance. The same could be said about the hour shift in time, as both are connected by their importance to the circadian rhythm. The circadian rhythm is a vital link in the functioning of the entire body, including the brain. Electrical impulses and chemical interactions and reactions are at the root of every single bodily process, ranging from the production of hormones to essential metabolic processes to the ability of the brain to communicate with the body. The circadian rhythm helps to regulate the timing of these processes via an overarching system of body clocks that influence physical actions and processes down to the cellular level. Balanced, smooth functioning helps to produce good health and protect the body from disease.

Over countless generations, from our very origins as a species, we have evolved in conjunction with the pattern of day and night. That approximately 24-hour cycle of light and dark is a part of us and a part of how our bodies and minds work on a deep, mechanical level. Daylight Saving Time disrupts that significantly and not just by an hour lost or gained in sleeping time.

Due to that ancient evolutionary pattern, light is one of the primary environmental cues for our circadian rhythm. We have light sensitive cells in our retinas and brains that help to set our body clocks, thereby influencing the timing of bodily functions and brain tasks. The artificial shifting of sunrise and sunset times deprives us of the natural lighting patterns we need for a smooth adjustment to seasonal changes, allowing for the disruption of the highly complex systems that support health and well-being on the most basic levels. Science is increasingly demonstrating that such disruption is strongly linked to a wide range of diseases and chronic health conditions.

Prepare to Mitigate Impact

While scientists point to Standard Time as being best aligned to our what our circadian rhythms require for optimal functioning, many of us still have to deal with Daylight Saving Time. Preparing for the time change can help mitigate the impact. Start shifting your waking and sleeping times gradually a week or two in advance and practice good sleep hygiene. Add a little physical activity in morning sunlight to your daily routine to support your circadian rhythm. Lighten your evening meals and reduce your caffeine during your time transition phase. If the adjustment tends to be more difficult for you, consider a melatonin supplement to ease the transition.