The best reason for reading? Book lovers live longer, scientists say.

Good news on National Book Lovers Day: A chapter a day might keep the Grim Reaper away — at least a little longer.

A recent study by Yale University researchers, published online in the journal Social Science & Medicine, concluded that “book readers experienced a 20 percent reduction in risk of mortality over the 12 years of follow-up compared to non-book readers.”

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The data was obtained from a longitudinal Health and Retirement Study sponsored by the National Institute on Aging. The study looked at 3,635 subjects, all older than 50, whom the researchers divided into three groups: those who didn’t read books, those who read up to 3.5 hours a week and those who read more than 3.5 hours a week.

The findings were remarkable: Book readers survived almost two years longer than those who didn’t crack open a book.

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Accounting for variables such as education level, income and health status, the study found that those who read more than 3.5 hours weekly were 23 percent less likely to die during that 12-year period. Those who read up to 3.5 hours — an average of a half-hour a day — were 17 percent less likely.

In other words, just like a healthy diet and exercise, books appear to promote a “significant survival advantage,” the authors concluded.

Why or how that’s the case remains unclear; the research showed only an association between book reading and longevity, not a causal relationship. But the findings are not so surprising. Other recent research showed that reading novels appears to boost both brain connectivity and empathy.

Book buying has increased annually during the past few years. At least 652 million print and electronic books were sold in the United States in 2015, according to Nielsen BookScan, the main data collector for the book publishing industry.

The bad news: Americans barely crack the top 25 when it comes to which countries read the most books. India, Thailand and China are ranked one, two and three by the World Culture Index, while the United States comes in 23rd, behind countries such as Egypt, Australia, Turkey and Germany.

The better news is that 80 percent of young adults in America read a book last year, compared with 68 percent of those between the ages of 50 and 64, according to a Pew Research Center survey.

Unfortunately, the Yale researchers said longevity was not increased by reading newspapers.