The Effects of Daylight Saving Time Clock Changes on Mental and Physical Health in England: Evidence from the Clinical Practice Research Datalink (CPRD)

OBJECTIVES

To explore the effects of daylight saving time clock changes on mental and physical health events in primary and secondary care in England.

DESIGN

Population-based study using linked electronic health records.

SETTING

English primary care practices contributing to the Clinical Practice Research Datalink (CPRD) Gold database, linked to hospital admissions and Accident and Emergency (A&E) data.

PARTICIPANTS

683,809 individuals (road traffic injuries: all ages, cardiovascular disease (CVD): aged ≥40 years, all other conditions: ≥10 years) registered with a participating English GP practice, with a health event for one of our health conditions in their primary or secondary care record in the eight weeks surrounding the Spring or Autumn clock changes between 2008 and 2019.

MAIN OUTCOME MEASURES

Health events were defined as a diagnosis code (or symptom code and prescription for mental health outcomes in primary care) of anxiety, major acute CVD, depression, eating disorder, road traffic injury, self-harm or sleep disorder in primary or secondary care, or psychiatric condition in A&E. Negative binomial regression models, adjusted for day of the week and region (and Easter weekend in Spring), compared event rates in the week after the clock changes to the control period (four weeks before the changes and weeks two-four after).

RESULTS

In the week after the Autumn clock change five health conditions had fewer events, including: anxiety (IRR 0.97, 95% CI 0.95 to 0.98), acute CVD (IRR 0.98, 95% CI 0.96 to 0.999), depression (IRR 0.96, 95% CI 0.95 to 0.97), psychiatric conditions (IRR: 0.94, 95% CI 0.90 to 0.98) and sleep disorders (IRR 0.92, 95% CI 0.87 to 0.97). There was little evidence of reductions in eating disorder diagnoses, road traffic injuries or self-harm.

CONCLUSIONS

There was a reduction in rates of CVD, sleep disorders and mental health disorders after the Autumn clock change, but little evidence that the Spring clock change affected health.

What is already known on this topic

• Studies suggest that the DST clock changes, particularly the Spring clock change, have a detrimental effect on population health.

• On this basis, sleep societies have unanimously called for the clock changes to be abolished and recommend GMT be adopted year-round.

• In 2019, the EU voted to end the practice of changing the clocks. However, it is not clear whether England will do the same.

What this study adds

• This extensive study of the effects of the DST clock changes on health in England used a large, representative GP and hospital dataset, and examined multiple health conditions.

• This study estimates the effects of the clock changes on demand for NHS services.

• In the week after the Autumn clock change there was a decrease in health events for sleep disorders, CVD, anxiety, depression and psychiatric conditions.