Autumn Clock Change Linked to Fewer Heart and Mental Health Events in England: Study Shows
UK: A large population-based study from England suggests that daylight saving time (DST) clock changes have differing short-term effects on health, with the autumn clock change linked to modest reductions in several mental and physical health events, while the spring change shows little impact. The findings were published in the BMJ by Melanie A. de Lange from the MRC Integrative Epidemiology Unit, Bristol Medical School, University of Bristol, and colleagues.
Daylight saving time has long been debated for its potential influence on sleep, mental well-being, and cardiovascular health. Earlier studies—largely conducted outside the UK—have raised concerns that the spring clock change, when clocks move forward by one hour, may adversely affect population health. These concerns have fueled calls from sleep societies to abolish clock changes altogether and adopt Greenwich Mean Time year-round. However, UK-specific evidence has been limited.
To address this gap, researchers conducted a retrospective cohort study using data from the Clinical Practice Research Datalink (CPRD) GOLD, linked with hospital admissions and accident and emergency records. The analysis included 683,809 individuals registered with English general practices who experienced a health event within eight weeks before or after spring or autumn clock changes between 2008 and 2019. The study covered a wide age range, including all ages for road traffic injuries, adults aged 40 years and older for cardiovascular disease, and individuals aged 10 years and above for other conditions.
The investigators examined acute changes in health events recorded in primary and secondary care, focusing on anxiety, depression, acute cardiovascular disease, psychiatric conditions, sleep disorders, eating disorders, self-harm, and road traffic injuries. Event rates in the week after each clock change were compared with control periods using adjusted statistical models that accounted for day of the week, geographic region, and seasonal factors.
Key Findings:
- The week after the autumn clock change was associated with a reduction in recorded health events across several conditions.
- Modest declines were observed in rates of anxiety, depression, psychiatric conditions, sleep disorders, and acute cardiovascular disease following the autumn clock change.
- Little evidence was found of changes in eating disorder diagnoses after the autumn clock change.
- Rates of road traffic injuries and self-harm did not show meaningful variation following the autumn clock change.
- The spring clock change was not associated with significant increases or decreases in any of the health outcomes examined.
The authors caution that electronic health records reflect the date a clinician records a diagnosis rather than the precise onset of symptoms. Nevertheless, the use of a large, representative dataset allowed the researchers to estimate how clock changes may influence short-term demand for NHS services across England.
Overall, the findings suggest that the autumn DST clock change may be linked to short-term reductions in cardiovascular, sleep-related, and mental health events, whereas the spring change appears to have minimal effect. The researchers conclude that further studies are needed to better understand the mechanisms behind these observations and to inform ongoing policy discussions about the future of daylight saving time in England.
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