This weekend, Britons will pay a familiar toll for longer summer evenings: the loss of a precious hour’s sleep. At 1am on Sunday, the clocks spring forward, marking the start of British Summer Time (BST) and interrupting the delicate biological rhythms of millions.
The Body’s Internal Clock Thrown Off Gear
While designed to maximise daylight, the shift has an immediate physiological cost. The core issue is the forcible disruption of the body’s circadian rhythm, the internal clock governed by light and darkness. According to Dr Sue Peacock, a consultant health psychologist specialising in sleep disorders, the key agent in this disruption is melatonin, the hormone produced by the brain’s pineal gland that regulates the sleep-wake cycle. “It is secreted in response to darkness and helps us feel tired and ready for bed – and is suppressed by light,” she explains. The sudden increase in evening daylight can delay melatonin production, making it harder to fall asleep at the usual time just as the clock demands earlier rising.
For some, this adjustment can take several days, leading to a domino effect of grogginess, fatigue, and reduced alertness. The impact is not merely one of feeling tired. Research indicates more serious health consequences are linked to this annual jolt. Studies have pointed to an increase in heart attacks of up to 24% in the first working week after the spring change, alongside rises in strokes and atrial fibrillation. The British Sleep Society, which advocates for abolishing clock changes, links the disruption to these cardiovascular risks and an elevated chance of accidents on roads and in workplaces due to impaired reaction times.
Certain groups are especially vulnerable. Children, teenagers—whose circadian rhythms are naturally delayed during puberty—shift workers, older adults, and those with existing sleep or heart conditions find the adjustment particularly difficult. The disturbance can also exacerbate mental health issues, leading to increased irritability, anxiety, and low mood.
A Practice With A Wartime Past And A Divided Present
The concept of daylight saving in Britain dates back to 1916, inspired by William Willett’s “The Waste of Daylight” campaign and initially adopted to conserve energy during the First World War. The current system is governed by the Summer Time Act 1972, with dates aligned to former European Union directives: clocks spring forward at 1am on the last Sunday in March and fall back on the last Sunday in October. In 2026, for instance, the changes will fall on March 29 and October 25.
The rationale has long centred on making better use of daylight, with arguments citing benefits for road safety, leisure, tourism, and economic activity in the evenings. However, critics contend these benefits are now outdated and outweighed by the health and productivity costs, with some studies even suggesting a negative impact on currency values. Public opinion remains split, with polls showing a near-even division between those who support the biannual change and those who wish to scrap it. If abolished, a majority would prefer permanent summer time.
Despite the debate and a 2019 European Parliament vote to end seasonal changes, the UK government has stated it has no plans to alter the current arrangements. This leaves individuals to manage the consequences themselves each spring.
How To Steer Your Body Through The Shift
Sleep experts advise that preparation is key to mitigating the effects. A gradual approach is most effective. In the days leading up to Sunday, try shifting your bedtime and waking time by 10-15 minutes earlier each day to ease the transition. On the day itself, aim to eat your evening meal a little earlier.
Light exposure is your strongest tool for resetting your internal clock. Seek out natural sunlight, especially in the morning, to signal wakefulness to your body. Conversely, as the evenings stay lighter, create a dark sleep environment using blackout curtains or a sleep mask to encourage melatonin production. Be stringent with sleep hygiene: maintain a consistent routine, even at weekends, and avoid caffeine and alcohol before bed.
Finally, limit exposure to the blue light emitted by phones, tablets, and laptops in the evening, as it tricks the brain into staying alert. Resist the urge to scroll in bed or have a long lie-in on Sunday morning, as both can further delay adjustment. Staying hydrated, particularly in the morning, can also help combat fatigue as your body adapts to the new timetable.