As you've heard, it's healthy to exercise, socialize, volunteer and get enough sleep, to the point of extending your life. Now a new study indicates that reading books can keep you alive longer as well. So if that's your inclination in the heat of August and you have time at a beach or beside a lake or lounging in a cool room, you can congratulate yourself: You're not only being lazy. "The benefits of reading books include a longer life in which to read them," the authors, a team at the Yale School of Public Health, conclude.

The team found 3,635 participants in the nationally representative Health and Retirement Study, a survey of people age 50 and up, who provided information about their reading patterns. The question they investigated was whether people who read books lived longer than people who didn't—and whether reading newspapers and magazines was just as good for you.

After taking account of an impressive list of factors—age, sex, race, education, comorbidities, self-rated health, wealth, marital status, and depression—the team concluded that book readers lived 23 months longer. Another way of crunching the numbers revealed that, over a 12-year period, book-readers cut their chance of dying by 20 percent, and reading books, they found, did more for health than reading other media.

Perhaps summer is your time for novels. There's also a fresh study concluding that reading literary fiction makes healthy volunteers better at "mentalizing"—putting yourself in another's person's shoes, as your high-school English teacher should have explained. Subjects were randomly assigned to read a book classified as literary fiction, non-fiction or science fiction. Other earlier research has found that reading short stories makes us less in need of "closure," more open-minded.

I applaud these conclusions, of course. It's gratifying to cite science to back up my own instincts. On the other hand, I can't imagine any of these studies seeing the light of day if they said the opposite. Their purpose is to support teaching literature and encourage us all to read books, at a time when book people are in a panic.

It may surprise you to hear that Americans read books at all. According to Pew's 2015 report, 72 percent of Americans said they'd read a book in the last year, including e-books. That figure is down from 79 percent four years earlier, although the survey organization says the intensity of book-reading among those who do it has remained stable. The scary statistic is the increase in non-readers, which has nearly tripled since 1978.

Millennials, however, do read more than blogs. Fully 80 percent of citizens ages 18 to 29 reported that they'd read a book that year, compared with 69 percent of those 65 and older. Perhaps these literate young people will devour books in their senior years, when we think of ourselves as having more time.

But it's healthy to exercise, socialize, volunteer and get enough sleep. Sitting all morning without talking or helping anyone or staying up until 2 a.m. with my book doesn't seem like a healthy activity. I'm always a little afraid I'll die young curled up with a book, or fail to have a life at all. It may comfort you to know that book-readers are also more likely to exercise and volunteer. We find the time, somehow.

Reading books probably isn't a bargain, longevity-wise. In the Yale study, on average, people who read books did so about about four hours a week. It took only 75 minutes of brisk walking or the equivalent weekly to get nearly two more years of life in a separate study, of people ages 40 and up. Could you in particular, extend your life even further if you spent more of your book-reading time playing volleyball or cooking at home? Would reading a novel help you better understand your kids or neighbors or wife? That remains your own puzzle.

Temma Ehrenfeld is a writer in New York.