Seven hours of sleep a night and lots of reading. That seems to be the magic formula for keeping mentally alert into old age, according to the findings of a new study out of Spain.

After analyzing the lifestyles of 245 seniors aged 65 and older, researchers from the CEU Cardenal Herrera University in Valencia, Spain found that those who slept either too much or too little and abstained from brain-stimulating activities like reading were at increased risk of developing cognitive impairment.

According to their study, published in the journal Revista de Investigacion Clinica, seniors who slept more than eight hours or less than six, were 2.6 times more likely to suffer from cognitive impairment compared to those who got six to eight hours a night.

Likewise, the absence of brain-boosting activities like reading also contributed to cognitive decline: Those who admitted to not reading were 3.7 times at increased risk, while those who said they read occasionally increased their risk by 2.5 times.

Overall, 12 per cent of the participants suffered from cognitive impairment.

Researchers point out that age-related cognitive decline affects 35.6 million people worldwide. According to the World Alzheimer Report, that figure is expected to spike to 100 million cases in 2050.

Other known lifestyle habits that can help seniors keep their brain sharp is to adopt a regular exercise regime and a healthy diet that includes brain-boosting foods rich in omega-3s and antioxidants.