Keeping the heating turned off is one surefire way of reducing gas and electricity bills this winter, but it could come at the expense of people’s health – particularly those with heart and lung conditions.

According to a survey of more than 2,000 UK adults, 23% are planning to do without heating this winter, while about 70% said they planned to turn their heating on less. Yet each centigrade degree reduction below 18C in Britain has been calculated to correspond with an extra 3,500 deaths. Here are the main ways in which cold homes can contribute to worse health.

Cardiovascular disease

Low temperatures cause blood vessels to narrow, putting stress on the circulatory system. “[This] can lead to cardiovascular effects, including ischaemic heart disease (IHD), coronary heart disease, strokes, subarachnoid haemorrhage and death,” according to the World Health Organization’s housing and health guidelines.

A review of the impact of cold homes on health from the UCL Institute of Health Equity and Public Health England, published in 2014, also highlighted the problem, pointing to data that suggested deaths from cardiovascular disease in England were higher in winterthan the average for other times for the year.

Circulatory problems tend to kick in once temperatures fall below about 12C. “[This] results in raised blood pressure, caused by the narrowing of blood vessels, which can lead to increases in blood thickness as fluid is lost from circulation,” the report says. “Increased blood pressure, and increased blood viscosity, can increase the risk of strokes and heart attacks.”

Asthma

Cold air also affects the function of the respiratory tract, with problems starting once the temperature drops below about 16C (61F). Those with existing respiratory conditions, such as asthma or chronic obstructive pulmonary disease (COPD), are at greatest risk.

Sarah MacFadyen, the head of policy and external affairs at Asthma + Lung UK, said: “Winter is the deadliest season for people with lung conditions, and we’re deeply concerned that energy price hikes will leave tens of thousands of people unable to heat their homes and fighting for breath.

“Breathing in cold air irritates your airways, and your lungs react by becoming tighter, which makes it more difficult to breathe. The cold is a common trigger for people with conditions like COPD and asthma and leads to life-threatening flare-ups and attacks.”

Cold homes are also more susceptible to damp and mould growth, which can trigger allergies, including breathing difficulties in susceptible individuals. Children living in cold, damp and mouldy homes are between 1.5 and three times more likely to develop symptoms of asthma than those living in warm and dry homes, the UCL report says.

A report published in 2015 for Friends of the Earth noted that while Sweden experienced a colder climate and harsher winters, the proportion of people admitted to hospital with respiratory problems, including asthma, over the previous five years was far higher in England. A key driver, the organisation stressed, was that English homes tended to be a less energy efficient than Swedish ones, as they had less insulation.

Already, Asthma + Lung UK is experiencing an increase in calls to its helpline and visits to its website. MacFadyen said: “We’re worried we’re going to see a sharp decline in the country’s lung health this winter.”

Respiratory infections

Cold homes can also increase the risk of respiratory infections. Certain viruses, such as common cold-causing rhinoviruses, replicate faster in cold noses, while parts of the immune system also become less effective in lower temperatures.

For instance, Akiko Iwasaki at Yale University and her colleagues showed that cells lining the airways of mice produced fewer immune-rallying interferon molecules at lower temperatures.

This could have serious consequences for people with respiratory conditions, such as COPD, as it may increase the risk of chest infections.

Dr Andrew Whittamore, a practising GP and clinical lead at Asthma + Lung UK, said: “Having a cold home could put people with lung conditions more at risk of getting a respiratory infection. This is because cold and flu viruses, which can cause respiratory infections, thrive in colder temperatures and poorly ventilated, damp environments. Long-term exposure to colder temperatures and mould can also affect our immune response, hampering our ability to fight off respiratory infections.”

Sleep

Body temperature needs to drop by about 1C to initiate sleep, which is why many people struggle to fall asleep during hot weather. However, trying to fall asleep in a bedroom that’s too cold can also be difficult. The main way our bodies reduce their temperature in the run-up to sleep is by increasing blood flow to the extremities. This diverts heat away from the core and causes it to radiate into our environment.

But being too cold causes the blood vessels in our skin to constrict, making it harder to dump this excess heat. According to the Sleep Charity, an ideal bedroom temperature is about 16-18C, although this varies from person to person. Below about 12C, many people may struggle to drop off. Using a hot water bottle to gently warm the feet can help increase blood flow to the skin. Bed socks, and additional layers of clothing and bedding, can also help.

Depression

A review by Christine Liddell and Ciara Guiney at the University of Ulster found that living in cold and damp housing contributed to a variety of mental health stressors, including persistent worry about debt and affordability, physical discomfort and worry about the consequences of cold and damp for people’s health. “Improvements to energy efficiency are often associated with significant improvements in mental wellbeing,” the researchers said.

According to a report by UCL’s Marmot review team, published in 2011, more than one in four adolescents living in cold housing are at risk of mental health problems compared with one in 20 who have always lived in warm housing.

The report also cites an evaluation of the government’s Warm Front scheme, which was introduced in 2000 and offered a package of heating and insulation measures to people on certain benefits in England. It found that people’s chances of avoiding depression increased as their bedroom temperatures rose.