Nimoy has been diagnosed with chronic obstructive pulmonary disease after he quit smoking three decades ago. Also known as COPD, the disease is one of the most common lung diseases and can cause coughing, wheezing, shortness of breath and chest tightness. "I'm doing OK," he tweeted Thursday. "Just can't walk distances. Love my life, family, friends and followers."
After disclosing his diagnosis, Nimoy is now speaking out against the dangers of smoking. "Smokers, please understand. If you quit after you're diagnosed with lung damage, it's too late," he also tweeted Thursday. "Grandpa says learn my lesson. Quit now."