Here’s good news for readers. Book reading, sometimes maligned as a sedentary behavior that may harm your health, actually increases your life expectancy. This according to a study by Avni Bavishi and two colleagues from the Yale University School of Public Health. Since this is a correlational study, and correlation does not imply causation, it’s worth looking at their methods in some detail.
The data came from 3635 participants in the University of Michigan’s Health and Retirement Study, a nationally representative sample of adults over 50. They were interviewed every other year between 2001 and 2012, during which time 27.4% of them died. Participants were asked how many hours they spent during the past week reading books. They were asked the same question regarding periodicals (magazines and newspapers). The average time spent reading books was 3.92 hours a week; for periodicals, it was 6.10 hours. The correlation between book and periodical reading was modest (r = .23).
The authors predicted that the effect of book reading on life expectancy would be mediated by cognitive engagement; that is, reading books causes you to think about them, which in turn increases your longevity. Cognitive engagement was measured by performance on eight mental tasks, including immediate and delayed recall, backward counting and object naming.
In a correlational study such as this, it is important to control for alternative explanations that might cause both reading and longevity. Three variables predicted greater book reading in their sample. Women read more than men, people with more education read more, and so did higher income people. The statistical analysis held these three variables constant, plus an impressive list of others: age, race, visual acuity, marital status, job status, depression, self-rated health, and the presence of seven health problems (cancer, heart disease, diabetes, etc.). The analysis also controlled for cognitive engagement scores at the beginning of the study.
The results showed that book reading increased longevity, and that the more time you spend reading, the greater the effect. The effect of reading books was greater than that of reading magazines and newspapers. By the end of the study, 27% of the book readers had died, compared to 33% of non-readers. Comparing book readers and non-readers at the time at which 20% of the participants had died, the readers had a survival advantage of 23 months.
As predicted, the effect of book reading on longevity was mediated by cognitive engagement. (See this earlier post for an explanation of mediational analysis.) The researchers suggested two ways in which reading books increases cognitive engagement. First of all, book reading is deep reading, meaning that the greater length of books encourages readers to ask questions as they go along and to draw connections between various parts of the book. Secondly, book reading promotes empathy with the persons you are reading about, which might lead to greater social intelligence.
Of course, it’s impossible to rule out all possible alternative explanations for these results. I’m troubled by the lack of control for the participants’ social capital—the sum total of people’s involvement in community life-–which is known to be related to good health and life expectancy. However, the relationship between social capital and reading is unclear. You could argue that people who are involved in the community have less time to read. On the other hand, community involvement may encourage reading. People may read books in order to discuss them with other people, who in turn may suggest new books to read.
If these findings are valid, they raise several interesting questions. For example, would listening to audiobooks produce the same survival advantage? That is, is it the act of reading that is beneficial, or is it the content, regardless of how it is accessed? Of course, content must have some effect, since periodicals were less beneficial than books. Future researchers might want to look at the differences between fiction and non-fiction, or between genres or topics. Mysteries, for example, would seem to encourage deep reading.
As the authors note, the average American over 65 spends 4.4 hours per day watching television. In a 2012 study similar to this one, Peter Meunnig and his colleagues found that TV viewing reduced longevity. Specifically, each hour of daily viewing cost their participants about 1.2 years of life expectancy. The effect was mediated by greater unhappiness, reduced social capital and lower confidence in social institutions. If people could be persuaded to spend some of that 4.4 hours reading instead, they might be doing themselves a favor in more ways than one.
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