Spring forward, fall back: daylight saving time and its effects on human health

mclapham9
2 days ago
4 min read

a person dressed in red rushing past a wall of clocks — a person dressed in red, rushing by a wall of clocks; photo courtesy of Unsplash

Daylight saving time begins in March and ends in November; learn how to protect your health and well-being despite the twice-yearly time change.

What is daylight savings time?

The first Sunday in November traditionally marks the end of daylight-saving time. In the United States, clocks are turned back one hour to standard time. This change results in a gain of an hour of daylight at the start of the day.

Daylight-saving time (DST) was first introduced in the U.S. in 1918 (1). The Standard Time Act was instituted for seven months during World War I. The intent was to conserve energy resources through the addition of daylight hours. During World War II, year-round daylight-saving time was implemented, again to conserve energy for the war efforts (1). After WWII, communities were given the choice to continue DST or change back to standard time. This continued until 1966 when the Uniform Time Act standardized DST (1). During the winter of 1974, permanent DST was enacted but was repealed a year later as parents were concerned about children walking to school in the dark (1).

DST and its effects on your health

DST has repeatedly been shown to have adverse effects on health. Disruptions in human circadian rhythms are a key part of the effect of DST on humans and their health (2, 3, 4).

Human circadian rhythms are natural fluctuations that occur roughly every 24 hours. These fluctuations occur in response to changes in the length of light and dark periods in the environment.

In humans, the circadian clock is located in the hypothalamus. The clock’s primary responsibility is to coordinate biological processes such as sleep/wake cycles, metabolism and stress hormones. The hypothalamus monitors these processes, so they occur at the correct time to maximize the ability of an individual to thrive in their environment (2, 3, 4).

DST has been shown to negatively effect health in humans by disrupting the circadian rhythm. DST has been shown repeatedly to increase health risks. The effects of DST on human health and well-being are varied (2, 3, 4, 5, 7,8):

Increase in ED visits
Increase in missed medical appointments
Increase in auto accidents for the first few days after time changes
Association with mood disturbances and suicide
Increase in cardiovascular events such as heart attacks and atrial fibrillation
Disruption of sleep patterns and resulting sleep deprivation
Increase in fatigue and drowsy driving
Increases in blood pressure and heart rate
Worsening of depression, anxiety and seasonal affective disorder
Reduction in work productivity
Increase in stress hormones which trigger inflammation
Decrease in insulin sensitivity

There is also maybe a link between DST and higher rates of obesity and stroke (6). A study at Stanford University in 2025 compared the circadian health impact of permanent standard time (ST), permanent DST and biannual switching. By utilizing the U.S models of circadian rhythm and health data from the CDC, the Stanford researchers discovered the change to permanent ST was predicted to reduce obesity by 2.6 million cases and stroke by 300,000 cases (6). The researchers urged caution regarding the results and stated additional research was needed to take into consideration the economic and safety impacts of changing the U.S. time policy.

There is disagreement amongst world-wide time experts regarding the benefits of a shift to permanent DST vs. a shift to permanent ST. The American Academy of Sleep Medicine supports “the elimination of daylight-saving time. A change to permanent standard time is best aligned with human circadian biology and has the potential to produce beneficial effects for public health and safety” (7).

The future of DST

In the U.S., some states have passed legislation to implement permanent DST. However, these bills would require Congress to change federal U.S. time policies before these bills could take effect. As of 2025, polling results indicate 54% of Americans favor the permanent end of DST and prefer to switching to permanent ST. The least favorable stance was continuing the current twice per year time changes.

Ways to safeguard your health and well-being during time changes

Some folks prepare for time changes by gradually adjusting their sleep time beginning a few weeks before the time change. This means getting to bed 15 to 30 minutes earlier than your usual bedtime to help your body make up for the lost hour. It is important to maintain your daily schedule despite gaining or losing an hour of sleep (9, 10).

It’s important to adopt a year-round healthy lifestyle to boost your resilience especially when time changes occur. Ways to boost your health year-round include (9, 10):

Maintaining a consistent sleep routine, which is essential to avoiding the sleep disruption which can occur with time changes. Consistency means going to sleep and getting up the same time, every day, even on weekends.
Daily exposure to early morning sunlight will help reset your circadian clock.
Daily exercise can also assist in resetting your internal clock, especially morning exercise.
Reduce your exposure to screens (TV, phone, computer) 1-2 hours before bedtime to reduce disruption to melatonin production. Melatonin is the hormone which tells your brain it’s time to sleep.
Consuming a healthy diet, which includes adequate protein intake and the inclusion of complex carbohydrates such as whole grains, fruits and vegetables, also helps to boost wellness.

Unfortunately, there appears to be no end to the inevitable biannual time changes. Until the U.S. Congress passes time-change legislation, take the time and make the effort to safeguard your health to prevent or avoid the health risks associated with twice-yearly time changes.

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Assessed and Endorsed by the MedReport Medical Review Board