From the American Psychological Society:
…researchers learned that those with higher IQ scores lived longer, a result consistent with other studies. The study also showed that characteristics significantly related to death included male gender and smoking. But Deary and Der also found something new – faster reaction times seemed an even better predictor of long life than IQ.
There are different ways the results could be interpreted. Slow reaction times could reflect a degeneration of the brain, which in turn could reflect degenerating physical health (an obvious possible cause of earlier mortality). But in another study the IQs of 11-year-old subjects also were found to predict life span length, just as accurately as it did for the middle-aged participants in Deary and Der’s 14-year study.