Leonard Nimoy, best known as Mr. Spock of "Star Trek," warned fans about smoking before he died from a lung disease Friday. Nimoy, 83, announced on Twitter this month that to "live long and prosper," fans needed to quit tobacco. "I quit smoking 30 yrs ago. Not soon enough. I have COPD. Grandpa says, quit now!! LLAP," he tweeted.

A few days later, he rang the alarm again. "Smokers, please understand. If you quit after you're diagnosed with lung damage it's too late. Grandpa says learn my lesson. Quit now," he tweeted, adding, "I'm doing OK. Just can't walk distances. Love my life, family, friends and followers."

Chronic obstructive pulmonary disease (COPD) is one of the most common lung diseases. It can make breathing difficult. It includes chronic bronchitis, which involves a long-term cough with mucus, and emphysema, or damage to the lungs over time.

The Centers for Disease Control and Prevention estimates that about 15 million Americans have been diagnosed with chronic obstructive pulmonary disease. It is the third leading cause of death in the U.S. Smoking is the main trigger for COPD. Symptoms include fatigue, shortness of breath and wheezing. 

People aged 65-74 are more likely to have COPD. So are non-Hispanic whites, women and those with a history of asthma.

In his 1975 autobiography, "I Am Not Spock," Nimoy wrote, “In Spock, I finally found the best of both worlds: to be widely accepted in public approval and yet be able to continue to play the insulated alien through the Vulcan character.”

“Star Trek” premiered on NBC on Sept. 8, 1966, making Nimoy a star. Gene Roddenberry, the creator of the franchise, called him “the conscience" of the sometimes campy science fiction show about the distant future.