Cold weather, short days and feeling tired.

Quick answer. There is little direct evidence that cold air on its own makes healthy people tired. What clearly changes in a UK winter is daylight, movement and routine: a UK study found adults sat more and spent more time in bed in winter, and studies of the body clock show it responds to shorter days. Daylight, regular activity and a steady sleep routine are the practical answers, and tiredness that lasts for weeks is a reason to see a GP.

Does cold weather make you tired?

The honest answer is that nobody has shown it clearly. When people say the cold makes them tired, they usually mean winter, and winter changes several things at once: the temperature, the amount of daylight, how much people move and when they go to bed. Studies rarely separate the cold from the rest.

The research on temperature and sleep is reassuring for anyone with a warm bed. A review in the Journal of Physiological Anthropology found that in real-life conditions, with bedding and nightclothes, "cold exposure does not affect sleep stages, though the use of beddings and clothing during sleep is critical in supporting thermoregulation and sleep in cold exposure" (Okamoto-Mizuno and Mizuno, 2012). In the same real-life conditions, heat increased time spent awake. The authors also note that cold still affects the body during sleep in other ways, and call for more research.

That fits the NHS's own sleep advice: "You may find it easier to sleep in a room that is quiet, dark and cool" (NHS Every Mind Matters). A cool bedroom is fine. Being cold in bed is not, so the duvet matters more than the thermostat.

Does winter make you tired? What the research shows.

Three studies are useful here, each for a different reason.

• Less everyday movement, more sitting. A UK study tracked 46 adults with activity monitors for a week in each season. Light-intensity activity was higher in spring and summer. Sitting time and time in bed were higher in winter. Total sleep time and moderate to vigorous exercise did not change with the season (O'Connell and colleagues, 2014).
• A body clock that follows the seasons. Researchers in Colorado had people camp with only natural light, in summer and in winter. They concluded that "the human circadian clock adapts to seasonal changes in the natural light-dark cycle", with a longer biological night in winter than in summer (Stothard and colleagues, 2017).
• Possibly more sleep in winter. A Berlin study of 188 patients at a sleep clinic found REM sleep about 30 minutes longer in winter than in spring. Total sleep was up to 60 minutes longer in winter than in summer, but that difference was not statistically significant (Seidler and colleagues, 2023).

How much daylight is there in a UK winter?

Much less than most people picture. These day lengths are calculated for the 21st of each month this winter, from sunrise to sunset.

For comparison, London had 16h 38m on 21 June. Times can differ by a minute from published tables. On a working weekday in December, most of the daylight falls while people are indoors.

What is known, and what is not.

Put together, the evidence supports a few plain statements and leaves some questions open.

Reasonably well established.

• UK winter days are short, and the shortest have under 8 hours of daylight in London and under 7 in Edinburgh.
• People tend to move less in light, everyday ways in winter and spend more time sitting.
• The body clock takes its timing from light, and responds to the length of the day.

Not settled.

• Whether cold air by itself makes healthy people tired.
• Whether healthy adults need more sleep in winter. The Berlin authors say that only "if replicated in a healthy population" would their data point to adjusting sleep habits to the season.

How to feel less tired when it is cold and dark.

The changes that help are the ones that put back what winter takes away.

• Get daylight in the middle of the day. From November it is often the only daylight a working day offers. A walk at lunchtime counts.
• Keep moving. The NHS says "regular exercise will make you feel less tired in the long run" (NHS: self-help tips to fight tiredness). If the dark has stopped your evening walk or run, move it rather than drop it. Our guide to running through a UK winter covers doing it safely.
• Keep the same sleep times. The NHS's tiredness advice is to "try to stick to the same sleep times and aim for 6 to 9 hours of sleep" (NHS: tiredness and fatigue). More time in bed is not the same as more sleep.
• Warm bed, cool room. Layers and a proper duvet, with the room itself kept cool.
• Eat regularly. The NHS suggests "regular meals and healthy snacks every 3 to 4 hours". Cold mornings make a planned breakfast more likely to happen.

We wrote more on the routine side in why winter makes you so tired. If you have been tired for a few weeks and do not know why, the NHS advises seeing a GP.

Where Immufix fits.

Immufix is one 25g scoop in around 200ml of water, once a day, and most people take it with breakfast. Vitamin C, riboflavin, niacin, pantothenic acid, vitamin B6, folic acid and magnesium contribute to the reduction of tiredness and fatigue. Magnesium also contributes to normal muscle function. It is a food supplement, so it sits alongside daylight, movement and sleep rather than replacing any of them. Every amount is listed on the science page.

The short version.

• There is little direct evidence that cold air on its own makes healthy people tired.
• At its shortest, a winter day in London has under 8 hours of daylight, and people tend to sit more and spend longer in bed.
• The body clock responds to shorter days. Whether healthy adults need more sleep in winter is not settled.
• Daylight at lunchtime, regular movement, fixed sleep times and a warm bed in a cool room help most.
• Tiredness that lasts for weeks is a question for a GP.

Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you have a medical condition, are pregnant, breastfeeding or taking medication, speak to your GP or pharmacist before taking any food supplement.