The lungs hide more secrets about our health than we imagine. With every breath, they are exposed to pollutants, microbes, dust, and allergens—an everyday burden that accelerates their natural wear. What’s striking, however, is that the condition of the lungs doesn’t affect breathing alone; it is directly linked to overall health, the immune system, body weight, and even brain function.

In May 2025, an international team of respiratory medicine experts published one of the first studies to map how lung function changes with age. The study was based on data from around 30,000 men and women collected over decades and was conducted with the participation of the Karolinska Institutet.

The results showed that peak lung function occurs in the early to mid–third decade of life, appearing slightly earlier in women than in men. From that point on, a gradual decline follows.

When and why lung function declines

According to Judith Garcia-Aymerich, professor at the Barcelona Institute for Global Health and lead author of the study, this decline appears to be biologically part of aging. Factors such as smoking, air pollution, and disease flare-ups can further accelerate the process.

However, the better our lung function is at its peak, the greater our “reserve” against chronic respiratory diseases later in life. And the benefit doesn’t stop there: good lung health is also associated with a lower risk of cardiometabolic diseases, immune disorders, and cognitive decline.

A simple at-home lung test

Although scientific studies use specialized equipment, there is a simple way to estimate your lung capacity at home.

You will need:

• a large plastic bottle
• a bucket or bathtub
• a rubber tube

The process is based on measuring forced vital capacity (FVC), that is, the volume of air you can exhale after a deep inhalation.

How to do the test step by step

To perform the test, first fill the plastic bottle with water in successive amounts of 200 ml (about one small glass), marking the level each time with a marker, until it is completely full. Then place the bottle upside down in a bucket or bathtub filled with water, making sure it remains full.

Holding the bottle in this position, place the rubber tube into its opening; it doesn’t need to fit perfectly. After taking a deep breath, exhale steadily into the tube and observe how many of the marked lines on the bottle “empty.”

The number of lines that move is multiplied by 200 ml, giving an indicative volume of air that the lungs can exhale in one effort. This is a simplified estimate of forced vital capacity (FVC), a marker widely used in assessing lung function.

Caution! As scientists emphasize, this test does not replace medical examinations and cannot be used for diagnosis, but it does provide a general picture of respiratory capacity.

According to John Dickinson, head of clinical exercise respiratory physiology at the University of Kent, the test shows how much air the lungs can expel. As he notes, as far back as the 19th century it had been observed that individuals with very low vital capacity had a shorter life expectancy.

The American Lung Association reports that even in healthy people who have never smoked, FVC decreases by about 0.2 liters per decade simply due to aging.

Why the lungs affect the whole body

As we age, lung tissue loses elasticity, respiratory muscles weaken, and the rib cage becomes less flexible. If the loss of function is significant, it can lead to shortness of breath and conditions such as chronic obstructive pulmonary disease (COPD).

Dawn Bowdish, professor at McMaster University, explains that the lungs are closely connected to the heart, circulation, and immune system through the so-called “lung–immunity axis.” When inflammation in the lungs increases, it can affect the entire body.

How to improve lung function

The good news is that there are ways to protect and strengthen your lungs:

• Regular exercise, which reduces inflammation and strengthens respiratory muscles
• Quitting smoking and vaping
• A balanced diet, with less salt and more antioxidants
• Maintaining a healthy body weight, as abdominal fat restricts full lung expansion

The decline in lung function with age is inevitable, but not uncontrollable. The lungs respond to care, exercise, and healthy lifestyle choices. And the better we take care of them, the more “breaths of health” we gain for the future—literally and figuratively.