Many people don't realize they have lung damage. Our experts reveal how you can test your lung function and improve your lung health.

You can lose a significant amount of lung function and not realize you may have lung damage. “We have a lot of spare capacity in our organs. You can damage a fair amount of the lungs without realizing you have any problems,” says Dr. Anna Day, a respirologist at Women’s College Hospital and professor of medicine at the University of Toronto.

How can you test your lung function?
Take a spirometry test. This noninvasive test measures the size of your breath and how well you  can empty your lungs. Your doctor  will ask you to take a deep breath and blow as hard as you can into a tube attached to a computer that measures lung volume and expiratory flow. You will be asked to repeat the exercise at least three times to ensure accuracy, and you may be given medication to see if it improves your lung function. This test can 
help diagnose and manage chronic obstructive pulmonary disease (COPD) and asthma. People at risk for COPD and asthma (risk factors include smoking or occupational exposure to lung irritants) can lose lung function without having 
any symptoms, says Dr. Day, who recommends at-risk patients undergo this test once a year. It can be performed at your doctor’s office, a lab or a hospital.

Four things that can affect lung health:
1. Being overweight: Extra pounds can make your lungs smaller when excess weight puts pressure on the chest walls. “People who are very overweight or who have a big stomach can decrease their usable lung size,” says Dr. Day.

2. Inhaling toxins: Smoking tobacco, marijuana or other drugs 
can damage your lungs. Also, exposure to occupational hazards such as sandblasting, irritants, toxic fumes 
and asbestos can lead to reduced 
lung function.

3. Aging: As people age, they experience some asymptomatic loss of lung function that does not require therapy. They may also lose lung volume because of changes in posture, such as a back curvature (kyphosis), says Dr. Day.

4. Bad posture: "Posture is important to lung health,” says Dr. Day. Studies show that slumped sitting significantly decreases lung capacity and expiratory flow.