Saving light, losing lives: How daylight saving time impacts deaths from suicide and substance abuse

Deaths of despair-associated mortality rates globally: a 2000-2019 sex-specific disparities analysis

OBJECTIVES

The aim of this study was to explore sex-specific disparities in rates of deaths of despair across 183 countries from 2000 to 2019.

STUDY DESIGN

Secondary analysis of cross-sectional population-level data.

METHODS

Data were obtained from the World Health Organization Health Inequality Data Repository. We analysed data on mortality due to alcohol, drug-use disorders, and self-harm (as a proxy for suicide). We calculated the average rate of deaths of despair by year and sex, trends in these rates, and cause-specific mortality trends. We then fitted mixed-effect generalised linear models to compare mortality rates by sex and country.

RESULTS

Analyses revealed significant disparities by sex, with a 3.3-fold higher rate among men than among women globally (95% confidence interval: 3.1-3.5, P < 0.001). There was a significant decline in deaths of despair globally and among both sexes during the assessed period (5% per 5 years). Lesotho, Belarus, the US, the Russian Federation, Guyana, and Slovenia ranked among the top 10 countries out of 183 with the highest mortality rates for both sexes. Canada, the Republic of Korea, Belgium, and Finland were countries with the highest mortality rates among women, whereas Ukraine, Lithuania, Mongolia, and Eswatini have the highest rates among men. In the US, 5-year mortality rates increased by 35% for women and 21% for men: drug-use mortality showed a significant increase over time, whereas suicide rates decreased for both sexes in the given country. Additionally, mortality rates from alcohol use decreased among women.

CONCLUSIONS

This global analysis shed light on health disparities by sex in deaths of despair, especially concerning trends in the US. It identified countries and groups in need of targeted mental health and substance-use programs. Moreover, the disparities by sex revealed in this analysis suggest that mental health and substance-use interventions and programs may need to be more attentive to sex and/or gender, such as inequitable social norms and restrictive forms of masculinities, which have been shown to be contributing factors to deaths of despair.

The British Sleep Society position statement on Daylight Saving Time in the UK

There is an ongoing debate in the United Kingdom and in other countries about whether twice-yearly changes into and out of Daylight Saving Time should be abolished. Opinions are divided about whether any abolition of Daylight Saving Time should result in permanent Standard Time, or year-long Daylight Saving Time. The British Sleep Society concludes from the available scientific evidence that circadian and sleep health are affected negatively by enforced changes of clock time (especially in a forward direction) and positively by the availability of natural daylight during the morning. Thus, our recommendation is that the United Kingdom should abolish the twice-yearly clock change and reinstate Standard Time throughout the year.

Temperature exposure and sleep duration: Evidence from time use surveys

The Earth's climate is projected to warm significantly in the 21st century, and this will affect human societies in many ways. Since sleep is a basic human need and part of everyone's life, the question of how temperature affects human sleep naturally arises. This paper examines the effect of daily mean temperature on sleep duration using nationally representative Hungarian time use surveys between 1976 and 2010. Compared to a day with an average temperature of 5-10 °C, colder temperatures do not influence sleep duration. However, as daily mean temperatures rise, sleep duration starts to strongly decline. The effect of a hot (>25 °C) day is -13.3 minutes, but if preceded by a few other hot days, the effect is even stronger, -24.7 minutes. The estimated sleep loss is especially large on weekends and public holidays, for older individuals, and men. Combining the estimated effects with temperature projections of twenty-four climate models shows that the warming climate will substantially decrease sleep duration. The projected impacts are especially large when taking into account the effects of heatwave days. This study also shows that different groups in society are likely to be affected in significantly different ways by a warming climate.

Daylight saving time was not associated with a change in suicide rates in Austria, Switzerland and Sweden

BACKGROUND

Some studies have reported an increase in suicides after the start of daylight saving time (DST), but the evidence is mixed and more research about proposed mechanisms (disrupted sleep, changing light exposure) is needed.

METHODS

In our preregistered study, we analyzed change in suicide rates in the 2 weeks before/after DST, based on data between 1980 and 2022 from Austria, Switzerland and Sweden, using Poisson regression models and changepoint analyses. To explore the impact of disrupted sleep, we repeated the analysis for retired people who are likely less bound to DST, and for younger people. To explore the effect of changed daylight exposure, we repeated the analysis for northern and southern regions because twilight and daylight exposure varies by latitude.

RESULTS

Suicide rates did not significantly increase after the start of DST (adjusted incidence rate ratio IRR = 0.98, 95% CI 0.91-1.06, P = 0.66, n = 13 362 suicides) or after DST ended (adjusted IRR = 0.99, 95% CI 0.91-1.07, P = 0.76, n = 12 319 suicides). There were no statistically significant findings among younger or older subgroups and also not in Sweden and Austria/Switzerland. No changepoints were detected.

CONCLUSIONS

There were no significant changes in suicide rates associated with DST and no clear evidence to support proposed mechanisms (light exposure, disruption of sleep). Our study is one of the largest and was adequately powered. Nonetheless, even larger studies to detect smaller effects could be important to inform the debate about harms and benefits of DST.

Permanent standard time is the optimal choice for health and safety: an American Academy of Sleep Medicine position statement

The period of the year from spring to fall, when clocks in most parts of the United States are set one hour ahead of standard time, is called daylight saving time, and its beginning and ending dates and times are set by federal law. The human biological clock is regulated by the timing of light and darkness, which then dictates sleep and wake rhythms. In daily life, the timing of exposure to light is generally linked to the social clock. When the solar clock is misaligned with the social clock, desynchronization occurs between the internal circadian rhythm and the social clock. The yearly change between standard time and daylight saving time introduces this misalignment, which has been associated with risks to physical and mental health and safety, as well as risks to public health. In 2020, the American Academy of Sleep Medicine (AASM) published a position statement advocating for the elimination of seasonal time changes, suggesting that evidence best supports the adoption of year-round standard time. This updated statement cites new evidence and support for permanent standard time. It is the position of the AASM that the United States should eliminate seasonal time changes in favor of permanent standard time, which aligns best with human circadian biology. Evidence supports the distinct benefits of standard time for health and safety, while also underscoring the potential harms that result from seasonal time changes to and from daylight saving time.

CITATION

Rishi MA, Cheng JY, Strang AR, et al. Permanent standard time is the optimal choice for health and safety: an American Academy of Sleep Medicine position statement. J Clin Sleep Med. 2024;20(1):121-125.

The controversy over daylight saving time: evidence for and against

PURPOSE OF REVIEW

Biannual clock changes to and from daylight saving time have been pervasive in many societies for over 50 years. Governments are considering abandoning this practice and choosing a single permanent time.

RECENT FINDINGS

Our endogenous circadian clock follows our photoperiod, which changes over the year. The acute disruption caused by changing our clocks can affect safety (motor vehicle and on the job accidents), health (cardiovascular disease, drug overdoses, suicide), and human behavior (sport performance, generosity, and procrastination). Although abandoning the clock change could help avoid these acute harms, choosing the wrong permanent time could lead to chronic circadian misalignment, which could have even more profound implications for health, safety, and human behavior.

SUMMARY

Ceasing the biannual clock change may be a good choice, but governments need to be mindful of which permanent time to adopt. Many regions of the world already follow the wrong time during standard time, and circadian misalignment would be amplified by moving to permanent daylight saving time. In many regions, Standard Time better aligns with our circadian clock, thus providing a more natural light cycle that minimizes circadian misalignment.

Longitude-based time zone partitions and rates of suicide

BACKGROUND

Increasing evidence suggests that conditions with decreased morning and increased evening light exposure, including shift work, daylight-saving time, and eveningness, are associated with elevated mortality and suicide risk. Given that the alignment between the astronomical, biological, and social time varies across a time zone, with later-shifted daylight exposure in the western partition, we hypothesized that western time zone partitions would have higher suicide rates than eastern partitions.

METHODS

United States (U.S.) county-level suicide and demographic data, from 2010 to 2018, were obtained from a Centers for Disease Control database. Using longitude and latitude, counties were sorted into the western, middle, or eastern partition of their respective time zones, as well as the northern and southern halves of the U.S. Linear regressions were used to estimate the associations between suicide rates and time zone partitions, adjusting for gender, race, ethnicity, age group, and unemployment rates.

RESULTS

Data were available for 2872 counties. Across the U.S., western partitions had statistically significantly higher rates of suicide compared to eastern partitions and averaged up to two additional yearly deaths per 100,000 people (p < .001).

LIMITATIONS

Ecological design and limited adjustment for socioeconomic factors.

CONCLUSIONS

To our knowledge, this is the first study of the relationship between longitude-based time zone partitions and suicide. The results were consistent with the hypothesized elevated suicide rates in the western partitions, and concordant with previous reports on cancer mortality and transportation fatalities. The next step is to retest the hypothesis with individual-level data, accounting for latitude, photoperiodic changes, daylight-saving time, geoclimatic variables, physical and mental health indicators, as well as socioeconomic adversity and protection.