Are you someone who struggles to get a good night’s sleep? If so, don’t expect to be refreshed when you wake up next Sunday morning. You will have automatically lost 60 minutes of precious shut-eye by virtue of the clock moving forward one hour on Saturday night.
Most of us settle back into our regular sleep pattern within days of the clock changing. However, for some, both the October gain and the March loss trigger more profound sleep disturbance. Our biological clock doesn’t like the time change. The additional morning light we have experienced in recent weeks acted as a natural wake-up alarm. Sunlight stimulates the biological clock to activate brain regions involved with maintaining wakefulness. However, starting next Sunday, the absence of this wake-promoting drive may create a sudden jet lag-type feeling. At the very least you may find it a little more difficult to get started in the mornings.
Scheduling this time change for a weekend also compounds the problem; for anyone who regularly enjoys a weekend lie-in, a greater shift in internal timing is required to get us back on track for the week ahead. It has been suggested that the clock change happening on a Friday night/Saturday morning, before we shift to weekend sleep timing, could make the transition easier.
Sleep-wake process
What’s happening in our brain during the sleep-wake process? It’s thought there are “wake-promoting” centres that use neurotransmitters such as serotonin to stimulate the arousal centres of the brain. Meanwhile, a small cluster of cells in the brain (called the ventrolateral preoptic nucleus – VLPO) is thought to monitor the sleepiness levels of the brain, triggering sleep when these levels become excessive.
It’s the reason we don’t wake up soon after falling asleep. Our sleepiness needs to be almost completely dissipated before the VLPO will switch off and allow us to wake up. But nerve cells in the VLPO tend to die off as we age – part of the reason our sleep quality declines later in life.
The body clock keeps the rhythmic variations of a number of bodily and behavioural functions – such as hormone production, temperature and digestion – in synchrony with each other. This process is called a circadian rhythm: from “circa” (about) and “die” (day).
Setting our clocks forward in spring is a real challenge to our body clock. For most of us our internal clock runs at slightly longer than 24 hours and requires a daily correction to remain in sync with the external 24-hour day. So adjusting our body clock earlier by an hour goes against this natural rhythm.
Daytime functioning
Research shows our daytime functioning is impaired for several days; the rate of car accidents increases on the Monday following the shift onto daylight saving time. And a number of studies have found a link between the clocks going forward and an increased risk of heart attacks.
A 2012 US study suggested a 10 per cent increased risk of having a heart attack in the 48 hours after the clock changes in spring. Meanwhile, Swedish researchers found a 7 per cent increase in the incidence of heart attacks in the first three weekdays after clocks went forward.
Turning clocks ahead an hour in spring or turning them back again in autumn is associated with a temporary increased incidence of stroke, a Finnish study shows. The increased stroke risk just after a transition to and from daylight savings time is probably related to interrupted sleep patterns, the researchers postulated.
Is there anything we can do to ameliorate these effects? It will help if you can shift the timing in your body clock in the days before next Sunday: begin going to bed earlier in increments of 15 minutes; limit exposure to mobile phone screens before bed; expose yourself to bright light in the morning; and avoid caffeine in the three to four hours before sleep.
mhouston@irishtimes.com @muirishouston