Legendary American actor and comedian Dick Van Dyke, who turned 100 on December 13, credits his longevity to his positive outlook and never getting angry. Numerous studies have found that keeping stress levels low and maintaining a positive, optimistic outlook are correlated with longevity. In the 1930s, researchers asked a group of 678 novice nuns to write an autobiography when they joined a convent, and compared their results with their long-term health outcomes. They found that women who expressed more positive emotion early in life lived an average of ten years longer than those whose writing tended to be more negative. A UK study also found that people who were more optimistic lived between 11% and 15% longer than their pessimistic counterparts. Another study found that around 160,000 women from a range of ethnic backgrounds were more likely to live into their 90s compared to pessimists. These findings could be explained by the effects of anger on our hearts, which can trigger the release of adrenaline and cortisol, the body's primary stress hormones, particularly in men. Stress has been linked to faster telomere shortening, which makes it harder for cells to communicate and renew, and meditation can help reduce stress.