Avni Bavishi, Martin Slade, and Becca Levy write in the abstract of their paper of 2016: “This study examined whether those who read books have a survival advantage over those who do not read books and over those who read other types of materials.” The authors conducted a 12-year follow-up in a Health and Retirement Study; 3635 people reported on habits of reading books, magazines, and newspapers. Information was also gathered about participants' age, sex, race, education, health care, wealth, marital status and depression.As compared with people those who did not do so, people who read books lived 23 months longer.
The difference remained substantial even when factors such as education, wealth, and so on, had been subtracted out. The researchers had not been able to include a measure of cognitive ability, such as IQ.
In a series of studies, Stanovich and colleagues (e.g. Stanovich et al., 1995) have found that the amount people read predicts cognitive outcomes such as vocabulary, skills of reasoning, and general knowledge, even when such factors as IQ and level of education have been subtracted out. In a follow-up study, Mar and Rain (2015) found that by far the largest effect on such outcomes came from the reading of fiction. A study by the National Endowment for the Arts indicated that 87% of book readers read fiction. Putting these studies together one may infer that it is likely that it was the reading of books of fiction that had the largest effect on longevity for the people in the study by Bavishi et al.
Bavishi, A., Slade, M. D., & Levy, B. R. (2016). A chapter a day: Association of book reading with longevity. Social Science and Medicine, 164, 44-48.
Mar, R. A., & Rain, M. (2015). Narrative fiction and expository nonfiction differentially predict verbal ability. Scientific Studies of Reading, 19, 419-433.
National Endowment for the Arts. (2009). Reading on the rise: A new chapter in American literacy. Washington, DC: National Endowment for the Arts.
Stanovich, K. E., West, R. F., & Harrison, M. R. (1995). Knowledge growth and maintenance across the life span: The role of print exposure. Developmental Psychology, 31, 811-826.