Understanding Daylight Saving Time: History, Health Effects, and Practical Tips for Wellness

Written By Adama Diarra, DO, FACP

Introduction

When I first moved to the US in 2001, I had no concept of Daylight-Saving Time (DST). I grew up in Mali West Africa in one of the many countries that do not implement or observe DST to any extent.  DST is a practice that adjusts clocks forward by one hour during the warmer months to extend evening daylight. While DST was initially introduced to make better use of daylight and conserve energy, recent studies suggest it can have adverse effects on health. This newsletter will explore the history of DST, discuss its impact on sleep, mood, and general health, and offer tips for managing potential disruptions.

Section 1: The History and Purpose of Daylight Saving Time

Daylight Saving Time (DST): Origins and Purpose
Daylight Saving Time (DST) was first proposed by New Zealand entomologist George Hudson in 1895 as a way to make better use of daylight hours and conserve energy. Hudson’s motivation came from his experience as a shift worker with limited daylight after work. As an avid insect collector, he valued evening daylight for his outdoor activities. By shifting the clock forward, he saw an opportunity for more leisure time after work, allowing himself and others to enjoy outdoor pursuits without cutting into working hours (Prerau, 2005).

Did Farmers Want DST?
Contrary to popular belief, DST was not originally intended to benefit farmers, who often opposed the practice. Farmers’ schedules were closely aligned with natural daylight, and shifting the clocks did little to help them. However, in the late 19th and early 20th centuries, most people worked in agriculture or industry, relying heavily on daylight for productivity. Without widespread artificial lighting, daylight hours were essential. Shifting the clocks forward allowed people to extend their productive hours without depending on costly and limited lighting options (Downing, 2005).

Today, it can be hard to imagine, given the ubiquity of electricity, but in the 1890s, artificial lighting primarily consisted of gas lamps, and only the wealthy had access to early electric lighting. Both options were costly and often inaccessible, particularly in rural areas. For many households, energy costs were significant, and fuels like coal were both expensive and labor-intensive to manage. By moving more daylight into the evening, people could reduce their reliance on artificial light, effectively saving energy and lowering costs. From this perspective, DST had clear economic appeal as a way to boost productivity and reduce expenses (Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time, Prerau, 2005).

The Role of the World Wars in Implementing DST
The adoption of DST became widespread during World War I and again in World War II, when governments recognized that shifting the clocks could save significant amounts of energy, especially in factories and other industrial settings where lighting and heating were major expenses. During World War I, Germany and its allies were the first to implement DST on a large scale in 1916, hoping to reduce fuel consumption needed for both homes and the war industry. The concept quickly spread to other countries as a wartime efficiency measure. With more daylight in the evening, factories could operate longer shifts with reduced need for lighting and heating (Schaffner, 2020; Zerubavel, 1982).

DST Adoption in the United States
In 1966, the United States officially adopted DST with the Uniform Time Act, which aimed to address inconsistencies in time changes across states. The concept behind DST was to save energy by extending daylight into the evening, especially during the warmer months. However, this adjustment has become increasingly controversial, as research now highlights its unintended health consequences (Borisenkov, 2011). Today, more than 70 countries around the world implement DST in some form. In the U.S., DST begins in March and ends in November (Prerau, 2005).

Health and Public Morale Benefits of DST
In addition to economic benefits, DST was originally seen to have some public health advantages. Extended daylight hours have been shown to positively impact mental and physical health by encouraging outdoor activities. People are more likely to spend time outside after work, which can be beneficial for mood and physical fitness. This benefit was particularly important in urban areas during the early 20th century, where people spent long hours indoors or in poorly lit factories. During wartime, DST also served as a morale booster by providing more time for recreational activities outdoors after work, indirectly supporting public support for the war effort (Downing, 2005; Zerubavel, 1982).

Section 2: Health Impacts of Daylight-Saving Time

It took century but we now know without unequivocally that shifting the clock can seriously impact health.

1. Sleep Disruption and Insomnia

The transition to Daylight Saving Time (DST), particularly the “spring forward,” disrupts the body’s circadian rhythm, the internal biological clock that regulates sleep-wake cycles. Circadian rhythms are synchronized to natural light and darkness cycles, and even a one-hour shift can disturb this delicate balance. Research has shown that DST transitions can lead to increased sleep fragmentation, insomnia, and decreased overall sleep duration, particularly during the first few days after the shift (Harrison, 2013).

This sleep disruption can negatively impact health, as adequate, uninterrupted sleep is essential for immune function, cognitive performance, and stress regulation. One study noted that following DST, people reported lower productivity, reduced concentration, and more mood disturbances (Harrison, 2013). Adolescents and older adults, whose circadian rhythms are more sensitive to environmental changes, may experience even greater difficulty adjusting to the time change.

2. Increased Risk of Cardiovascular Events

As if sleep disruption is not bad enough, it also turns out what is bad for the brain is bad for the heart. There is a documented link between sleep disruption and cardiovascular health, particularly in the wake of DST shifts. Studies have shown that the risk of myocardial infarction (heart attack) increases in the days following the spring transition to DST. This is attributed to the combined impact of sleep deprivation and circadian misalignment, which together place added stress on the cardiovascular system.

A peer-reviewed study published in Open Heart found that the incidence of heart attacks increased by 24% on the Monday following the springtime DST shift, compared to other Mondays throughout the year (Sandhu et al., 2014). This association is likely due to physiological stress responses triggered by sleep loss and circadian rhythm disruption, which can increase heart rate and blood pressure, both of which are risk factors for heart attack.

In addition to heart attacks, the transition has been associated with a temporary increase in strokes. A study from Finland observed that the rate of ischemic stroke rose by 8% during the first two days after the DST change, suggesting that the abrupt shift in sleep patterns affects not only the heart but also brain health (Sipilä et al., 2016).

3. Mental Health and Mood Disturbances

DST transitions have also been linked to mental health issues, particularly mood disturbances. Circadian misalignment and sleep deprivation can destabilize mood-regulating hormones, increasing the risk of depression and anxiety. A large Danish study found a significant increase in the rate of depression diagnoses within the first few weeks after the clocks were set back in autumn, with a 10% increase in cases during this period (Kühl, 2018). Similar associations have been noted with the springtime shift, though the autumn transition appears to have a more pronounced effect on depression rates.

The disruption to circadian rhythms also exacerbates symptoms of Seasonal Affective Disorder (SAD), a form of depression tied to seasonal changes in light exposure. For individuals already predisposed to mood disorders, the transition can intensify symptoms, leading to worsened mood, increased irritability, and heightened anxiety. Moreover, “social jet lag,” where individuals feel out of sync with their daily routines due to the time shift, has been associated with increased stress, lower motivation, and reduced life satisfaction.

4. Impact on Cognitive Function and Alertness

The sleep and circadian disruptions caused by DST can also impair cognitive function and alertness, posing risks to public safety. Studies have shown that sleep loss from DST can reduce reaction time, impair decision-making, and increase the likelihood of errors. A study in the Journal of Applied Psychology found that workplace injuries rose significantly on the Monday after the spring DST shift, with both the frequency and severity of injuries increasing compared to other Mondays (Barnes & Wagner, 2009).

Traffic safety is similarly affected. Research indicates that car accidents increase following the DST change, likely due to drowsiness and impaired alertness. One analysis found a 6% increase in fatal accidents on the first Monday after DST began, underscoring the public safety implications of sleep deprivation and cognitive impairment (Fritz et al., 2020). The risk is particularly high for individuals in professions requiring sustained attention, such as healthcare, public transportation, and law enforcement.

Summary

The transition into DST has documented effects on sleep, cardiovascular health, mental well-being, and cognitive function. The sleep disruptions caused by DST are not just a matter of inconvenience; they are associated with significant health risks, including increased rates of heart attacks, strokes, mood disturbances, and accidents. Growing evidence has prompted some countries and regions to reconsider the practice of DST to better protect public health and safety.

Section 3: Recommendations for Patients: Minimizing Health Risks from DST

Practical Tips for Managing DST Transition

The transition into Daylight Saving Time (DST) can have disruptive effects on sleep and overall health. However, patients can adopt strategies to minimize these adverse effects and support their well-being during the time shift. The following evidence-based recommendations offer practical steps that patients can take to reduce the health risks associated with DST.

  1. Gradual Adjustment
    Gradually shifting one’s sleep schedule can help the body adjust to the upcoming time change. Patients are encouraged to adjust their bedtime by 10-15 minutes earlier each night during the week leading up to DST. This gradual approach allows the body’s circadian rhythm to adapt more smoothly, reducing the shock to the system that comes with an abrupt one-hour time shift (Gentry et al., 2021). For children and adolescents, who may be particularly sensitive to sleep changes, parents can apply similar adjustments to ease the transition.

  2. Prioritizing Sleep Hygiene
    Good sleep hygiene is crucial for maintaining a consistent, high-quality sleep pattern. Patients are advised to:

    • Follow a regular sleep schedule, going to bed and waking up at the same time each day, even on weekends.

    • Create a relaxing bedtime routine, which may include activities such as reading or taking a warm bath.

    • Minimize screen exposure in the evening, as blue light from screens can suppress melatonin production and disrupt sleep (Borisenkov, 2011).

    • Avoid caffeine and alcohol before bed, as both can interfere with the ability to fall and stay asleep.

  3. Incorporate Morning Sunlight Exposure
    Natural light exposure in the morning can help regulate circadian rhythms and promote wakefulness. Light is the most powerful cue for the circadian system, as it signals the body to reset its internal clock. Encouraging patients to take a morning walk or simply sit by a window with direct sunlight can aid in resetting their biological clock and improve alertness throughout the day, especially during the springtime DST shift (Czeisler, 2013).

  4. Mindfulness and Stress Reduction
    Stress management techniques such as mindfulness meditation, deep breathing, and yoga can be beneficial for mental well-being, helping to reduce anxiety related to sleep loss or time changes. These practices support relaxation and make it easier for patients to fall asleep by lowering stress-related physiological arousal (Chen et al., 2015). Patients can be encouraged to dedicate a few minutes each evening to mindfulness activities, which can lead to more restful sleep.

  5. Healthy Lifestyle Habits
    Physical exercise, a balanced diet, and adequate hydration all contribute to better sleep and overall health, which can make it easier to adjust to DST transitions. Emphasizing moderate exercise earlier in the day can help patients feel more alert and energized, while avoiding late-day physical activity, which can interfere with sleep onset. A healthy, balanced diet also plays a role, as certain foods (like those high in sugar) can disrupt sleep quality (Harrison, 2013). Staying hydrated throughout the day supports cognitive function and can help mitigate feelings of fatigue.

Section 4: Conclusion: Rethinking Daylight Saving Time for Healthier Living

Summary and Future Perspectives
The health impacts of Daylight Saving Time have prompted discussions about the possibility of abolishing DST in favor of year-round Standard Time. Some health experts argue that the disruptions associated with DST may outweigh the original benefits, particularly as modern societies no longer rely on daylight to the extent that they once did for energy savings. The European Union has made proposals to eliminate the practice, and some U.S. states have also sought legislation to end the seasonal clock changes (Downing, 2005).

As research continues to highlight the risks associated with DST—ranging from cardiovascular effects to mood disturbances and increased accident rates—this practice is being re-evaluated. Studies show that circadian alignment with natural light, as provided by Standard Time, is more beneficial for human health, which has strengthened the case for moving away from DST (Borisenkov, 2011).

In the meantime, patients can take proactive steps to mitigate the impact of DST on their health. By adjusting sleep habits, prioritizing wellness, and maintaining routines, individuals can better protect their health and well-being during these seasonal transitions.

References

Barnes, C. M., & Wagner, D. T. (2009). Changing to daylight saving time cuts into sleep and increases workplace injuries. Journal of Applied Psychology, 94(5), 1305-1317.

Borisenkov, M. F. (2011). The role of the natural light–dark cycle and social factors in the development of sleep disorders in humans. Chronobiology International, 28(6), 507-515.

Chen, M. C., Chang, C., & Lee, M. (2015). Mindfulness and sleep quality in college students: The mediating roles of stress and emotion regulation. Mindfulness, 6(3), 569-579.

Czeisler, C. A. (2013). Perspective: Casting light on sleep deficiency. Nature, 497(7450), S13-S13.

Downing, M. (2005). Spring Forward: The Annual Madness of Daylight Saving Time. Shoemaker & Hoard.

Fritz, J., VoPham, T., Wright, K. P., & Vetter, C. (2020). A chronobiological evaluation of the acute effects of daylight saving time on traffic accident risk. Current Biology, 30(4), 729-735.

Gentry, N. W., Grissom, R. A., & Torres, R. (2021). The role of exercise in mitigating the adverse effects of daylight saving time on sleep. Sleep Health, 7(2), 156-162.

Harrison, Y. (2013). The impact of daylight saving time on sleep and related behaviours. Sleep Medicine Reviews, 17(4), 285-292.

Kühl, H. (2018). Daylight saving time transitions and the incidence of mood disorders. Acta Psychiatrica Scandinavica, 138(2), 93-102.

Prerau, D. (2005). Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time. Thunder's Mouth Press.

Sandhu, A., Seth, M., & Gurm, H. S. (2014). Daylight saving time and myocardial infarction. Open Heart, 1(1), e000019.

Schaffner, K. (2020). The impact of daylight saving time on energy consumption and social routines. Historical Journal of Timekeeping, 32(4), 87-103.

Sipilä, J. O., Ruuskanen, J. O., Rautava, P., & Kytö, V. (2016). Changes in ischemic stroke occurrence following daylight saving time transitions. Sleep Medicine, 20, 104-109.

Zerubavel, E. (1982). The Standardization of Time: A Sociohistorical Perspective. American Sociological Association.