Children who grow up at homes filled with books tend to have less cognitive（认知的）decrease when they reach old age, even when taking factors such as wealth and education into consideration.

Previous studies have found that children with large home libraries are more likely to do well at school and in their later careers. Ella Cohn-Schwartz at Ben-Gurion University of the Negev in Israel and her workmates wondered whether the benefits of early book exposure extend into old age.

They analyzed data from over 8000 men and women aged 65 and older without Alzheimer's disease in 16 European countries, who had taken memory tests in 2011 and 2013. The tests included trying to memorize lists of words and naming as many animals as possible in one minute. Participants were asked to recall how many books their family homes contained when they were children: no books, one shelf（about 25 books）, one bookcase （about 100 books）, two bookcases or more.

Those who grew up with larger book collections performed better in all memory tests. They also showed slower cognitive decrease, with a smaller drop in their test scores between 2011 and 2013. This may be because their early book exposure encouraged them to read more, which in turn improved their "cognitive reserve", says Cohn-Schwartz.

The findings remained the same when the researchers made adjustments for the participants' wealth, education, physical health and other factors. This suggests that large home libraries are not just a sign of having more money, they can also protect the brain in various ways, says Cohn-Schwartz.

Moreover, children who grow up at homes filled with books are probably also encouraged to take up other wholesome activities, doing sports, for example, which could also improve their cognitive reserve according to Ralph Martins at Edith Cow an University in Perth, Australia.