The Effects of Cystic Fibrosis (CF)

It’s important to know that CF symptoms affect different parts of the body over time. When talking about treatment for CF with your healthcare provider, there are some things you may want to discuss.

Lung Function

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People with CF tend to have thick, sticky mucus in their lungs. This makes it harder for the lungs to clear germs. This can lead to infection, a loss of lung function, and pulmonary exacerbations.

FEV1, or forced expiratory volume in 1 second, is a test that measures lung function using a spirometer. Often, a person’s FEV1 is compared with others of a similar age, sex, and height. This can be referred to as percent predicted FEV1, or ppFEV1.

  • On average, lung function in a person with CF (measured by the FEV1 test) declines 1 to 3 percentage points each year
  • Damage to the airways in the lungs may occur before a loss of lung function is even detected with an FEV1 test
  • Younger people with CF generally have greater lung function than older people with CF

Pulmonary Exacerbations

Pulmonary exacerbations are periods when CF symptoms get worse and require medical attention, including the use of an antibiotic. They may be a result of infections. During a pulmonary exacerbation, CF respiratory symptoms such as coughing and the amount of mucus in the lungs may increase. A person may also lose weight during a pulmonary exacerbation.

  • Lung function may decline faster in people who have more frequent pulmonary exacerbations
  • The lung damage caused by pulmonary exacerbations may be permanent


Most people with CF have a hard time absorbing fat, vitamins, and nutrients to get the calories they need to gain or maintain weight. Body mass index, or BMI, is used to determine a person’s nutritional health.

  • Proper nutrition is important for growth, and higher BMI is associated with better lung function in people with CF

Not sure what your BMI is?Enter your weight and height into the calculator below to find out.



Recommended BMI for adults with CF:

Men age 20+: ≥23 kg/m2

Women age 20+: ≥22 kg/m2

Be sure to discuss your BMI with your healthcare provider.

Some of the goals of CF treatment are to:

  • Maintain lung function, which includes reducing pulmonary exacerbations
  • Improve nutrition