The Effect of Daylight-Saving Time on Your Health

On Monday, I woke up confused. My dogs were still sound asleep, and my bedroom was very dark. Did I dream that my alarm went off? It did indeed wake me up, and I, like millions of others, was befuddled upon awakening in the dark. We didn’t imagine it; this was the effect of the change to daylight-saving time. Many of us stumbled through the day and needed more than that extra caffeine jolt to keep going. Yet, this happens every year. In October, we “fall back” by an hour, and in the spring, we “spring ahead.” Much debate has been about this twice-a-year tradition, so how did it begin?

Benjamin Franklin deserves some credit for this, though his recommendation was a joke. In a letter to the editor of a French newspaper, Franklin sarcastically recommended that Parisians get out of bed earlier to minimize their need for candles and lamp oil. He never mentioned changing the time. In 1895, entomologist George Hudson proposed the modern concept of daylight-saving time. He suggested a two-hour shift for more daylight to go bug hunting in the summer.

In the United States, daylight-saving time was first used in 1918, when a bill introduced the idea of a seasonal time shift. It lasted seven months before the bill was repealed. President Franklin Roosevelt re-established the idea of daylight-saving time. It was called "War Time” and lasted until the end of September 1945. The Uniform Time Act of 1966 established the concept of regulating a yearly time change.

In 2022, the Senate passed the Sunshine Protection Act, which would make daylight-saving time permanent starting in the spring of 2023. However, the bill wasn't taken up in the House, so it currently remains in limbo.

This may seem trivial compared to the many severe world events we are bombarded with daily. However, the time shift significantly impacts our physical and mental health.

All mammals function with a circadian rhythm, the 24-hour internal clock in our brain that regulates cycles of alertness and sleepiness, responding to light changes in our environment. Circadian clocks regulate metabolism in many systems and organs, including the heart, skeletal muscle, liver, and fatty tissue. The hour transition in the spring initially causes darker mornings and lighter evenings. A one-hour change may seem insignificant. However, sleep disruptions can lead to physical and mental health issues.

Cardiovascular Health

According to the American Heart Association, people experience an increase in heart attacks and strokes every year in the days following the time change. According to a study of hospital admissions across Michigan, there was a 24 percent increase in heart attacks on the Monday following the switch to daylight saving time. In a Finnish study, researchers found that the overall rate of ischemic stroke was 8 percent higher during the first two days after the daylight-saving time transition. Other research documents that, in general, more severe heart attacks occur on Mondays than on any other day of the week, making the day after the time change even more problematic.

One theory is that time changes impact sleep quality, which is intimately related to heart health. For example, a study published in the Journal of the American Heart Association found that variations in sleep duration of more than two hours a night within the same week were tied to developing atherosclerosis.

A different study published in Hypertension found that the link between excess weight and increased blood pressure was most significant among adolescents who had irregular sleep patterns. The Journal of the American Heart Association published a study documenting higher rates of an irregular heart rhythm called atrial fibrillation in women after menopause, citing poor sleep as a contributing factor.

Increase in Fatal Motor Vehicle Accidents

A 2020 study published in Current Biology examined 700,000 motor vehicle accidents over 20 years and found that the annual switch to daylight-saving time is associated with a 6 percent increase in fatal car crashes during the work week following the time change. An interesting finding was that when the Energy Policy Act extended daylight-saving time to March instead of April, fatalities also increased. Before that time, there was a consistent increase in deaths in April following the time change that occurred during those years. The study also showed changes in accident patterns after the "fall back" time change, with a decline in morning accidents and a spike in the evening when darkness comes sooner. These results were also attributed to disruptions in sleep. The authors suggest that it's better for sleep, the body clock, and overall health to have more morning light and less evening light during standard time.

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Mental Health

A well-known association exists between sleep and mental health. Insufficient sleep is linked to the development of many chronic diseases and conditions, including type 2 diabetes, cardiovascular disease, obesity, and depression. In the past 10 years, scientists discovered a macroscopic waste clearance system called the glymphatic system in the brain. During sleep, it flushes proteins and metabolites from the central nervous system and supplies the brain with nutrients. Decreased sleep results in less activity of this system. Due to the direct effect on sleep, daylight-saving time can worsen disorders such as anxiety, depression, and seasonal affective disorder. Less morning light during daylight-saving time can cause your body to produce lower serotonin levels, a mood-related neurotransmitter. Compounding that, longer evenings with more daylight will delay your body’s production of melatonin, a hormone that promotes sleep.

How to Minimize the Effects of the Time Change

• Change your sleep routine. Three days before the time change, go to bed and wake up 10 to 15 minutes earlier than usual. Try extending this over subsequent nights to a total of 45 minutes. This should help your body adjust to the lost hour.
• If needed, take afternoon naps for up to 30 minutes. Naps longer than that can make you feel even more tired.
• Increase your exposure to daylight. Try getting outside for 15 minutes in the morning, or consider using a lightbox.
• If possible, delay your morning schedule by an hour for the first week after the time change to allow your biological clock to adjust.
• Limit caffeine and alcohol, substances that can further disrupt your sleep.