Being too hot or too cold can be bad for your health. So, what is the optimum temperature for your home?

As someone who feels the cold – but is reluctant to constantly turn up the thermostat – a hot water bottle and a thick fleece are two of my closest friends. And as relentless winter storms sweep the east coast of the US and Canada – and other countries across the globe are trawling through what feels like a very long winter – you might also be wondering: what is the best indoor temperature for your health and comfort? The answer, it turns out, is not straightforward.

In the 1860s, German physician Carl Wunderlich took the temperatures of around 25,000 people and found that the average was 37C (98.6F). This figure has been widely accepted ever since. However, new data suggests that this isn't strictly true. Body temperature can vary between individuals, with modern research suggesting that gender, metabolism, hormones, activity, age and menstruation all have an influence. So, with such variations to consider, is there an optimum temperature at which to keep your home?

For countries with temperate or colder climates, guidance from the World Health Organization states that a room temperature of 18C (64.4F) is safe enough to protect us from the harmful effects of cold. Being in a cold, damp or draughty environment has negative physical and mental health consequences, from worsening asthma and increased risk of heart disease, to anxiety and depression.

"We recognise healthy homes are one of the key building blocks for good health. So that means homes that are accessible, safe, comfortable and warm help to protect our health, and support our communities to be healthy and resilient," says Rebecca Wilson, senior public health specialist at Public Health Wales in the UK, an organisation which advocates for improving links between homes and health.

The results of Public Health Wales's 2022 and 2023 winter surveys found that people were increasingly experiencing stress or anxiety in the three months leading up to winter due to rising heating costs (a jump from 57.2% to 66.5%). When the cold set in, more people set their thermostats to lower temperatures at home, and chose to heat specific rooms rather than the whole house – and, instead, turned to hot water bottles or blankets to stay warm.

"We know that all people who live in cold homes or face frugal poverty are affected. But the research does show that there's certain population groups such as older people, children, and people with disabilities and health conditions, who might be more impacted," says Wilson. (Read more about how cold homes can affect health).

Equally, overheating is also a health risk for those living in warmer climates, with an increased likelihood of heat exhaustion and heatstroke as the body desperately tries to cool itself, in turn putting stress on the heart and kidneys. Overheating can also exacerbate existing health conditions and negatively impact mental health, with links found to an increased suicide risk.

It's a bleak picture. Research has shown a global link between both cold and heat exposure and mortality over the 21st Century, with experts calling for more public awareness of non-optimal temperatures as a health risk. This is becoming an........

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