There's no doubt that you can be successful without being a social butterfly--just ask famous introverts like Bill Gates. But have you noticed that the office extroverts also don't take a ton of sick days? That's likely not because they have a bigger drive to go get 'em.
In a 2014 study by the University of Nottingham, researchers gathered blood samples for gene expression analysis. Participants also completed personality tests measuring the five major personality dimensions (extroversion, neuroticism, openness, agreeableness and conscientiousness). The researchers also gathered some basic information for control purposes, such as exercise habits.
The researchers discovered that, regardless of how the participants felt or the behaviors they claimed to do, extroversion was significantly associated with an increased expression of pro-inflammatory genes that help fight off disease. People with conscientious or more cautious personalities, however, had a reduced expression of pro-inflammatory genes. That is, extroverts showed stronger, more active immune systems.
The researchers note that they're not sure yet whether the personality trait influences the biology or the biology influences the personality. But their guess is that the result has to do with simple exposure. The more you are out and about with others, the more opportunities you have to come into contact with all kinds of different crud that can make you sick. So your body tells your immune system to hop to and do more work. That practice improves overall resistance to getting ill.
One takeaway from the study for leaders is that you might do the introverts on your team a health favor by reasonably encouraging them to participate in more social events. This doesn't mean they have to be in large groups that might make them more uncomfortable. It just means that it might be beneficial to have them interacting more overall.
Secondly, the workforce is diversifying to include more remote options. This naturally can reduce the short-term spread of disease, but in the long-term, extended remote work might have a negative effect on your team's ability to maintain healthy immune system activity. Introverted remote workers might face the highest risk of getting sick, as they might not be as likely as their extroverted counterparts to seek face-to-face interaction when not on the clock.
At the end of the day, both extroverts and introverts contribute significantly to the workforce, and both need leaders who take their unique health issues into consideration. Be observant and, within the boundaries of privacy, don't be afraid to ask your team what they individually and collectively need.