Sometimes, it's obvious when our health is under threat — but what about the things we can't see?
It's not always clearly visible when something is potentially causing harm, particularly when it comes to cardiovascular disease — a term used for conditions affecting the heart and blood vessels, including heart attacks and stroke - the leading cause of death worldwide.
So, what are some of the 'invisible' things that could be harming your heart?
"If you live in an area with high levels of air pollution, this can increase your risk of developing problems with your cardiovascular system," says Dr Ayyaz Sultan, consultant cardiologist at Pall Mall Medical (pallmallmedical.co.uk).
"The air pollutants can damage your blood vessels by making them narrower and harder, thus making it more difficult for blood to flow freely throughout your body. It can also affect your heart's electrical system thus causing abnormal heart rhythms, as well as potentially causing changes to the structure of the heart itself."
Avoiding too much time in obviously polluted air is a good idea — such as rooms filled with cigarette smoke and busy roads — and anyone concerned about their heart health should speak with their doctor.
We may not be able to see our cholesterol from the outside, but it's a major factor in cardiovascular problems — as it means fatty deposits can build up in the blood vessels, reducing blood flow and sometimes causing clots to form.
"Usually, high cholesterol has no symptoms," says Jules Payne, CEO of cholesterol charity Heart UK (heartuk.org.uk). "This means the only way you know you have a problem is to have a cholesterol test."
"Lots of factors play a part in maintaining healthy cholesterol levels. Eating too much saturated fat, smoking, drinking more alcohol than recommended and a lack of physical exercise can all increase your risk," Payne adds.
"Other things you can't change, like ageing or being of a South Asian background, can also increase your risk. Your genes can play a part too — familial hypercholesterolaemia (FH) can cause very high cholesterol, even if you have a healthy lifestyle. Keeping on top of your cholesterol levels is particularly important if you have suffered from a cardiovascular event in the past, like a heart attack or stroke, as around half of people who suffer a cardiovascular event experience a second event, on average within 114 days."
More information on managing cholesterol.
The same is true for high blood pressure, which rarely causes symptoms yet is a leading cause of strokes and heart attacks.
Anyone concerned should speak to their GP, especially if there's a family history of heart conditions. Similarly to cholesterol, lifestyle measures can help prevent and manage high blood pressure, but some people will need medication.
"The idea that your gut microbiome (the trillions of microorganisms living inside our intestinal tracts) impacts your cardiovascular health is not new, but more research is being done to study the link between the diversity of the microbiota and your risk of cardiovascular disease," says registered dietician and nutritionist, Sarah Schenker.
"There is evidence certain bacteria can impact your heart health, which has to do with the compounds these gut bacteria produce when they break down certain foods. These compounds can raise cholesterol levels, damage blood vessels and may lead to cardiovascular disease."
Diet is key for supporting the microbiome — eating plenty of fibre and a variety of veg, wholegrains, beans, legumes, etc. "Fermented foods contain probiotics and have also been associated with a lower risk of heart disease," adds Schenker. "Some research has shown that probiotics produced during fermentation can help restore the balance of friendly bacteria in your gut and modestly reduce blood pressure and help lower total and 'bad' LDL cholesterol."
For women, hormone changes due to menopause can influence cardiovascular disease risk.
"The hormone oestrogen is naturally produced in women and known to offer protection against cardiovascular disease. It does this by supporting your body to maintain healthy cholesterol levels," explains cardiovascular nurse Michaela Nuttall.
"Menopause causes the body to produce lower levels of oestrogen and can increase cholesterol levels, affect your blood pressure and change body fat distribution — all risk factors for a cardiovascular event, like a heart attack or stroke.
"But this is no reason to stress — there are simple steps you can take to improve your heart health during and after menopause," Nuttall assures.
"Choosing heart-healthy meals — such as incorporating more vegetables and swapping to wholegrain or wholemeal alternatives — and exercising regularly can help. Most importantly, speak with your healthcare professional and get regular check-ups, including cholesterol tests and blood pressure checks."
A 2018 study by The Heart Centre at Copenhagen University Hospital, which analysed data from thousands of patients with heart problems, found those who said they felt lonely had worse outcomes and higher mortality rates. Exactly why loneliness dents our health isn't always clear, but it's a recognised risk factor.
"In a post-pandemic world, a lot of people feel lonely, which can often lead to poor lifestyle habits like smoking or drinking more alcohol," says Nuttall. "It's important to know you can reach out to your GP for advice, and that you can improve your wellbeing through volunteering or joining local community groups."