Comedian and late night TV host Johnny Carson died in 2005 from emphysema. That and chronic bronchitis are the two most common forms of chronic obstructive pulmonary disease (COPD).

Smoking is the No. 1 cause of COPD (Carson smoked a lot, even on air), but it also can develop from exposure to air/industrial pollution.

COPD is now the third leading cause of death in the U.S.

Unfortunately, COPD often is diagnosed only when it's advanced. People dismiss shortness of breath or fatigue as signs of normal aging (they’re not), and they don't ask their doctor to investigate the true cause of such symptoms.

If you're one of the 11 to 15 million people in the U.S. with COPD, you're vulnerable to a roster of health problems, including heart disease, lung cancer, pulmonary high blood pressure, and depression.

Now, research has identified yet another reason why everyone with COPD needs to take extra care of him- or herself.

A study published in the journal Chest found that when people with COPD get the flu, one in five require intensive care, and one out of 10 die.

Even people with mild COPD who get the flu are more likely to develop pneumonia and other respiratory diseases.

So if you have COPD, it's important to get the flu vaccine — even if you have put it off.

And if you suffer from COPD and get the flu, see your doctor immediately.