The modern idea of "daylight saving" was first proposed in 1895 by George Vernon Hudson of New Zealand, with Germany and Austria-Hungary organizing the first national implementation in 1916. Since then the concept has garnered its share of both advocates and critics from around the world; changing our clocks benefits retailing, sports, and other activities that are happy to exploit the extra hours of sunlight. Of course it can also disrupt meetings, travel and record keeping and cause multiple other scheduling issues.
On a personal level, moving our clocks in either direction changes our principal time cue -morning sunlight- which controls our 24-hour circadian rhythm track. This means that our internal clock falls out of sync with our current day-night cycle. Our ability to adapt to this depends on several things.
Generally, "losing" an hour in the spring is more difficult to adjust to than "gaining" an hour in the fall. This is similar to the "flight lag" experienced in airplane travel; an earlier bedtime may cause difficulty falling asleep and increased wakefulness during the early part of the night. Conversely, setting the clocks back means we may fall asleep easily but can have a difficult time waking.
Our external time cues are called "zeitgeibers", and they include light, temperature, exercise and food/drink intake. It can take several days for our internal biological clock to re-synchronize with any new schedule, whether it's a clock change or a timezone difference. For some people, this can lead to disrupted sleep and feeling tired during the day (EDS).
Even if the actual time change doesn't affect your sleep, the change in seasons can; the lack of sunlight affects many people's moods despite a one hour change in time not being particularly important. For those who do feel affected, either physically or emotionally, this misalignment between external cues and our internal body clock can also have more serious consequences.
For example, statistics have long shown that the risk of heart attacks spikes on Monday mornings. This is thought to be due to a combination of stress brought on through the anticipation of a new working week, and the sudden changes in our sleep-wake cycle. A recent study published in the AAC journal Open Heart looked at the rates of heart attacks before and after our clock changes over 4 years, and found a 25% increase on the Monday following the shift to daylight saving time; conversely, there was a 21% decrease in heart attacks when the clocks were rolled back in the Autumn.
One of the best sleep practices for the winter months is avoiding bright light exposure at night, which can delay the body's internal clock. This includes computers, tv's, cellphones and tablets - so they shouldn't be in the bedroom.
Routine is key for maintaining a consistent drive to sleep each evening. In the winter, with fewer hours of daylight overall, it’s important to seek out exposure to morning light if you can. Light is a strong cue for your internal clock, and daylight ensures it remains synchronized to a 24-hour day even when your schedule changes slightly. Lack of light exposure during the day can result in a drift of the internal body clock to a longer than 24-hour rhythm, making it harder to get up in the morning in the winter. Here are some tips on how to make a smooth transition to the winter months:
- Start getting in sync early; try to eat, sleep, wake to the new time so that your circadian rhythm has a chance to adjust.
- Exercise earlier in the day to keep your energy levels high and to ensure you’re tired enough to get to sleep ‘earlier’, but be sure to avoid the over-stimulation effect of evening exercise.
- Get as much natural sunlight as possible: this will help adjust the body’s circadian rhythm. Dim lights in evening can help to induce sleepiness.
- Avoid alcohol and caffeine in the evenings and go for sleep-inducing foods and drinks.
- Nap wisely: avoid taking naps after 4pm and try to keep naps to no more than 10 - 20 minutes.