The condition of our lungs can reveal a great deal about our wider health. Luckily you can also get them into better shape.

How old do you think your lungs are? With every breath, they are exposed to a myriad of pollutants, microbes, dust and allergens. Unsurprisingly this can take a toll on these delicate organs, accelerating how they age. But they also can affect how the rest of your body ages too.

In early May 2025, an international team of respiratory experts published one of the first ever studies to assess how human lung function varies as we age. Based on data from some 30,000 men and women collected over the course of the 20th Century, it showed that our lung function peaks in our early to mid-20s. Women's lung capacity typically tops out a few years earlier than men's – before declining thereafter.

This, according to Judith Garcia-Aymerich, a professor at the Barcelona Institute for Global Health who led the study, appears to be a biologically programmed part of ageing, she says. Factors such as smoking, air pollution and flare-ups of conditions like asthma can all exacerbate this decline.

The better your lung capacity is at this peak age, however, the more resilience you will have against chronic respiratory diseases and other lung-related health conditions later in life, says Garcia-Aymerich. But lung health is also linked to a wide range of other more surprising aspects of your health, affecting your immune system, your weight and even your brain (read on to find out why later in this piece).

So just how healthy are your lungs? And can you do anything to improve the state they are in?

Studies like the one described above use expensive equipment to measure lung health, but there is a simple way to test your lungs at home. All you need is a large plastic bottle, a bucket or bathtub and a length of rubber tubing. And then do the following (you might want to do it in a sink or outside as it can get a bit messy):

1. First, measure out 200ml (7fl oz) of water into a measuring jug, transfer to the plastic bottle and use a pen to mark the water level.

2. Add another 200ml of water, mark the new water level and repeat the process until the bottle is full.

3. Fill the bucket or bathtub with water and dip the now full bottle into it, turning the bottle upside down under the water.

4. Keeping the bottle in this position, place the rubber tubing inside the bottle neck. It doesn't have to fit tightly.

5. Take a deep breath and blow into the tube.

6. Count how many lines of water you can blow out of the bottle.

7. Multiply the number of lines by 200ml. (eg three lines is 600ml). This number is your vital lung capacity, also referred to as forced vital capacity or FVC.

"The test looks at the volume of air you can breathe out, which has been termed vital [lung] capacity," says John Dickinson, who heads the exercise respiratory clinic at the University of Kent. "This term was first used by English surgeon John Hutchinson in the 1840s. He started to notice that those who could only breath small volumes of air had less time to live."

According to the American Lung Association, FVC can decrease by about 0.2 litres per decade, even in healthy people who have never smoked, due to the effects of ageing. Research suggests that a normal healthy FVC is between three and five litres.

Dickinson says that you should not be overly concerned if you get a lower reading from this home health test. "A lot of people will struggle to completely empty their lungs so may get false low readings," he says.

But there are also ways of improving your lung health and combating any decline in........

© BBC