Now a team comprised of researchers from the Department of Odontology and the Aging Research Center (ARC) at Karolinska Institutet and from Karlstad University have looked at tooth loss, chewing ability and cognitive function in a random nationwide sample of 557 people aged 77 or older. They found that those who had difficulty chewing hard food such as apples had a significantly higher risk of developing cognitive impairments. This correlation remained even when controlling for sex, age, education and mental health problems, variables that are often reported to impact on cognition. Whether chewing ability was sustained with natural teeth or dentures also had no bearing on the effect.