Pneumonia, a potentially deadly disease, is more common in people who smoke, according to a top Turkish physician.

“Cigarette smoking weakens the immune system and causes pneumonia,” said Dr. Filiz Kosar of the University of Health Sciences in Istanbul.

Pneumonia is mostly caused by infections produced by microorganisms such as bacteria, viruses, or fungi, she added, speaking with Anadolu Agency to mark the Prevention of Pneumonia Deaths Week.

Kosar stressed that the disease can lead to death, especially in children 5 years old and younger and people with structural lung disorders.

Read more: Smoking raises risk of contracting pneumonia