Our energy levels and mood can be affected by many factors, but our body clocks, or circadian rhythms, play a critical role. In the winter, our body clocks are more vulnerable to disruption because of lower levels of natural light.
So how can we overcome the effects that the changing clocks can have on our physical and mental wellbeing? Bensons for Beds’ resident sleep expert, Dr Sophie Bostock, explains.
The role of circadian rhythms
Circadian rhythms are 24-hour patterns that are hardwired into our DNA and control the timing of all our organs and bodily functions. Circadian rhythms represent the body’s logistics function: making the right things get to the right place at the right time. When the timing of all of our internal clocks is in sync, the body works efficiently, and we’re likely to feel energised and alert during the day and sleepy at night.
When our internal clocks go out of sync with each other or with the light-dark cycle of the sun, we experience circadian desynchrony. In other words, our internal systems are no longer working together, which puts stress on the body. This can cause fatigue, mood disturbances, changes in appetite and digestion, lower immunity, difficulty concentrating, and other changes.
The importance of light
Bright light from the sun is the most important cue that tells our brains that it’s daytime. Light in the morning is especially important to start our clocks for the day. and helps all our circadian rhythms align with each other. Natural daylight is thousands of times more intense than most indoor lighting, so when we stay inside all day, our body clocks can miss the daytime trigger and get confused about where we are in the 24-hour cycle.
In the UK and across the Northern Hemisphere, the Earth’s tilt away from the sun means that in the winter months, we are exposed to fewer hours of daylight. For example, in London, in June, on average, there are more than 16.5 hours of daylight, whereas in December, the average is fewer than 8 hours! The intensity of sunlight also decreases in the winter.
The effect of shorter days can be felt more acutely after the clocks change since we are more likely to “miss” a bit of daylight in the morning before we leave the house. If we’re at work inside all day, we may not have the opportunity to get any natural daylight.
In addition to circadian desynchrony, a lack of sunlight at the right time can directly impact our hormones. Sunlight triggers the production of serotonin, a neurotransmitter that promotes positive moods. Research has found that we typically produce less serotonin in the winter. Darkness triggers the production of melatonin, the hormone that signals the onset of sleep at night. If we miss out on morning sunlight, we’re less likely to banish lingering melatonin, and we can feel more lethargic.
The power of darkness for sleep
When talking about the importance of light, one thing that often gets overlooked is the importance of darkness for maintaining healthy circadian rhythms and good-quality sleep.
During sleep itself, you might assume that if your eyes are closed and you’re asleep, it doesn’t matter if there is a light left on. But recent research suggests that exposure to light at night can still impact your sleep quality.
In one study, 20 healthy young adults were monitored as they spent a few nights sleeping in either a dark room (<3 lux) or a dimly lit room (100 lux). Lux is a measure of light intensity. Most offices are lit to 250–500 lux, so 100 lux is just bright enough to read by. In the lit room, volunteers had less deep, slow-wave sleep and more light sleep. Their average heart rate during sleep was higher in the lit room than in the dark, and the following day, insulin resistance increased. Insulin resistance is a marker of risk for diabetes. This suggests that because light keeps us in a raised state of arousal, the quality of recovery in a dark room is higher than when the room is light.
What is seasonal affective disorder (SAD)?
Some people experience regular bouts of depression in the winter months, which naturally fade in the spring and summer. Clinically, seasonal affective disorder (SAD) is defined as a type of major depression that returns for at least two years in the winter months, often in combination with sleepiness and overeating. Other symptoms can include lack of energy, mood swings, anxiety, difficulty sleeping, alcohol or substance misuse, and social withdrawal.
In the northern hemisphere, estimates vary, but anything from 1–10% of the population may experience SAD. It is more common at latitudes above 30 degrees north or below 30 degrees south. It is rare around the equator, where there are fewer seasonal changes in light or temperature.
Is SAD different from the “winter blues”?
SAD is a form of clinical depression, which means it interferes with normal daily functioning in severe or disabling ways. Around 20–50% of the population experience a milder reduction in energy in the winter months, often termed the “winter blues”. Symptoms of the winter blues might include:
- Low energy. Feeling more tired or fatigued than usual
- Mood changes. Feelings of sadness, irritability, or a general sense of feeling down or not wanting to socialise
- Changes in sleep patterns. wanting to sleep more, difficulty waking up in the morning, oversleeping
What causes SAD and the winter blues?
As discussed above, lower levels of daylight during the winter months are thought to disrupt circadian rhythms, and cause hormonal changes, which can result in the winter blues, or SAD.
However, not everyone who experiences low light levels notices seasonal changes. It may be that some people have a genetic predisposition, or vulnerability – for example, they may be less sensitive to light, and so may need more light of greater intensity to regulate their internal rhythms.
There may also be psychological, behavioural and cultural factors at play. For example, in Northern Norway, although inhabitants of Tromso only get 2-3 hours of direct sunlight per day, rates of SAD are very low. They have a culture of getting outdoors to enjoy winter sports and embracing the cosiness of winter. It may therefore be that a positive mindset and regular physical activity – especially in social groups – can help to protect against the winter blues.
So, how can I wake up with more energy in the winter?
Firstly, if you’re worried that you might be experiencing Seasonal Affective Disorder, or severe mood disturbances or fatigue at any time of year, it’s important to speak to your GP or another medical professional for advice. They will be able to help find the right diagnosis, as well as recommend the best treatment.
If you’re looking for ways you can help yourself to feel better, and wake up with more energy, here are some tips:
- Light therapy, or phototherapy. Light therapy involves sitting or working near a special light therapy box, or SAD lamp, that emits bright artificial light, usually around 10,000 lux, every morning. The light box mimics natural outdoor light, aiming to make up for the reduced exposure to sunlight in the winter. Each lamp will have its own instructions, and it’s worth asking a specialist for advice, but I usually recommend that people sit 1–2 feet from a light box for 20–60 minutes at the same time each morning, to help re-set their circadian rhythms. Most studies suggest that light therapy can be effective within 7 days. Light therapy, with or without antidepressant medication, is often recommended as the first line treatment approach for SAD.
- Get as much natural daylight as possible. If you can get outside during the day, you may find that you can get similar benefits to light therapy, simply by spending time outdoors. One study found that the more hours of daylight reported, the better the sleep quality, the lower the rates of depression, and the greater the ease of getting out of bed in the morning. If this outdoor time is physically active, you could get double the benefits. Regular physical activity improves sleep quality, as well as being a natural mood booster.
- Try a dawn simulation alarm clock. If you struggle to get out of bed in the morning, a light alarm clock, or dawn simulation alarm clock, which gets gradually brighter before the alarm, may help you to reduce the groggy sleep inertia which some people experience on waking.
- Follow a consistent wake up schedule all week. The easiest way to help get your circadian rhythms in sync is to get out of bed at the same time each day, 7 days a week. Consistency of sleep timing is linked to better sleep quality.
- Switch off screens before bed. The light from screens is usually quite low intensity (<80 lux). While it is unlikely that this level of light will disrupt your circadian rhythms, screens can still be very disruptive to sleep. Reading work emails, for example, might make you feel stressed, and make it harder to sleep. Scrolling for hours or watching late night TV could delay bedtime, and make you feel more tired in the morning.
- Eat a natural, healthy diet. Many of us crave carbohydrate-rich “comfort food” in the winter. This may be one of the ways that our brain responds to less light, and circadian disruption. The problem with many sugary foods is that they trigger a “sugar crash” a few hours later. Aim for unprocessed foods which are high in protein and fibre to improve the quality of your sleep, and try to avoid large meals within the last two hours before getting into bed. A lack of sunlight on the skin also means many adults in the UK are deficient in Vitamin D, which can add to fatigue. The NHS recommends adults (including pregnant and breastfeeding women) should consider taking a daily supplement containing 10 micrograms of vitamin D from October to early March.