In Norway we like to wear T-shirts inside even in the middle of winter. And until very recently, electricity prices have been low enough that most of us have been able to do that.
Although a lot is changing now. The energy crisis in Europe and the period of skyrocketing electricity prices here in Norway has led many people to consider turning down the temperature in their living rooms.
But is it healthy for us?
If you’re young and healthy, you can probably cope with a slightly cold house. But the elderly and those at risk of heart disease should keep the temperature higher in some rooms, the researchers advise.
You can read a list of the researchers’ advice further down in the article.
Does being outside when it’s really cold make you more tired – even if you don’t do anything tiring?
According to Johan Øvrevik, we don’t know for sure how the temperature inside the house affects health. He is a researcher at the Department of Climate and Environmental Health at the Norwegian Institute of Public Health and a professor at the University of Oslo.
But there are some signs that suggest that the low temperature inside the house has an impact on health.
One of them is the controversy surrounding the phenomenon we call extreme winter mortality.
Influenza and heart disease
More people die in winter than in summer.
Some of these deaths are due to increased mortality from influenza during the winter season. There’s good reason to believe that temperature plays a role here, Øvrevik notes.
The dry, cold winter air can inhibit the immune system.
“When you breathe in cold air, you get less blood flow to your nose, and thus fewer immune cells that can fight infection,” he says.
Dry air can also dry out mucous membranes, which contributes to individuals becoming infected with viruses more easily. Additionally, it appears that viruses such as influenza and SARS-CoV-2 survive longer in dry air, therefore increasing the risk of infection.
However, influenza only explains a minor portion of excess winter mortality. Another important reason is heart disease.
James Mercer says, “Most people who die of heart disease in Norway are over 65. On average, 1,800 people die in the summer months such as June, compared to 2,500 for January.” He is Professor Emeritus at the University of the Arctic of Norway (UIT).
He has been interested in this phenomenon for decades.
The extreme winter mortality is well known throughout Europe. But the paradox is that where the winters are coldest, the problem is not the worst. opposite of this.
“The difference in mortality between summer and winter is smallest in Norway, Finland and other Scandinavian countries. It is largest in southern European countries such as Malta, Portugal and Cyprus, where winters are mild,” says Mercer.
This indicates that indoor temperature is important, both Mercer and Øvrevik argue.
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Homes in Tromso and Dublin compared
The difference is likely due to housing standards.
Norwegian houses are generally built to keep out the cold. They are well insulated and have efficient heating systems, such as the heating cables in the bathroom.
A few years ago, Mercer studied indoor temperatures in the homes of elderly people in Tromso in northern Norway and Dublin in Ireland.
The researchers installed equipment in 25 homes in each city to measure temperature in all living spaces. They recorded the temperature every two hours throughout the year.
The results showed big differences.
13 degrees in the bathroom
“In Tromsø, the temperature in the living room was 22 to 23 degrees year-round, while in Dublin it averaged 20 degrees,” says Mercer.
And in many other rooms it was much worse.
“The temperature in Irish kitchens was as low as 15 to 16 degrees in winter. The bathroom temperature in Tromsø is maintained at 23 to 24 degrees, whereas in Dublin the bathroom temperature is as low as 13 degrees in winter,” he says.
In Norway, the indoor temperature remained fairly uniform throughout the year, while in Ireland there was a large difference between summer and winter.
The exception was the bedroom. The bedrooms in Tromsø were around 14 degrees, while the Dublin bedrooms were 16 to 17 degrees.
“Norwegians like to sleep with the window open and have appropriate bed linen. In Ireland it’s the opposite,” says Mercer.
Many signs point to indoor climate
We do not know for sure whether these conditions are the reason for the significantly higher increase in winter mortality in Ireland and many other countries compared to Scandinavia. But many signs point in that direction, as well as the disparity in excess winter mortality across countries.
In the 1950s, for example, there was a big change in the heating of homes in Great Britain and Ireland, explains Mercer.
“They started using central heating in their homes, which had a big impact on the death rate,” he says.
Another clue is the population of Yakutsk in Siberia, one of the coldest cities in the world, Mercer believes.
The outdoor temperature here is extremely low for a large part of the year and the average temperature in January is below minus 40 degrees Celsius. Nevertheless, there is almost no increase in winter cardiovascular deaths among residents.
They have a comfortable indoor temperature and are very good at dressing appropriately when they go outside.
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mostly applies to people over 65
It is mainly older people who are at higher risk of death from exposure to cold, which may have physiological explanations.
As we age, says Mercer, changes occur in the body that make it harder to cope with low temperatures.
“We have reduced metabolism and muscle mass, and a lot of body fat. In addition, we are often less active and have less ability to shiver. Some older people also have less sensitivity to cold. They don’t really notice that they’re getting cold,” he says.
Previous research suggests that older people have a slightly lower skin temperature than younger people. In experiments where hands and feet were cooled in a controlled manner for a short period of time, it took longer for older people to regain their warmth.
blood pressure and cholesterol
Other changes that increase the risk of heart disease also occur.
Blood pressure rises, and levels of cholesterol and triglycerides in the blood increase. Research has shown that these risk factors vary throughout the seasons and are worst in the winter.
“When you’re cold, blood vessels in the surface of the skin, especially in the legs and arms, will constrict to keep heat in vital internal organs,” says Johan Øvrevik.
This means there are fewer places for your blood to travel, which raises your blood pressure.
A 2019 Japanese study showed that low indoor temperatures lead to high blood pressure, especially in older men. If you already have high blood pressure, a cold indoor environment can push your heart over the edge.
Both researchers do not want to scare anyone.
“Most young, healthy people will tolerate low indoor temperatures just fine,” Øvrevik says.
When it comes to elders, it is a different matter. It is important to know that too low an indoor temperature can be problematic, especially if it falls below 18 degrees. Older people and people with heart diseases therefore need to ensure that the environment inside their home is not too cold.
“One can imagine that many pensioners are considering keeping it cold to save electricity. It is very worrying,” he says.
Mercer generally thinks it’s a good idea to save some energy use by turning down the temperature a bit in Norwegian homes. but not too much.
They fear that too much ‘electricity savings’ could make Norway more like Ireland and other countries with a greater difference in mortality between summer and winter. This is not desirable.
Advice for the elderly – and for young people going out in a cold
Mercer recently gave some clear advice to the elderly in a brochure in collaboration with the Lions Club organization in Varanger:
- Keep an indoor thermometer.
- If you feel cold, it is cold, no matter what the thermometer shows. Get ready and turn up the heat.
- Keep at least one room in the house – the living room for example – really warm. preferably 24 degrees or more.
- Keep the temperature higher in bathrooms where you are often wearing light clothing.
- Feel free to keep it cool in the bedroom, but make sure you have proper, warm bed linens.
- Keep moving, it raises your body temperature and maintains muscle mass.
- dress well. Several thin layers of clothing are better than one thick layer.
- Eat hot food and drink hot drinks.
- Abstain from alcohol. A toddy may be perceived as warm, but it actually opens up blood vessels, causing you to lose heat.
Finally, Mercer offers a little advice for young people as well.
“Avoid snuff and tobacco if you are going out in the cold. Nicotine has the ability to dilate blood vessels, causing you to lose heat, for example from your hands and feet,” he says.
Translated by Alette Bjordal Gjellesvik.
Read the Norwegian version of this article on forskning.no