During the study, the researchers looked at 14,542 volunteer female nurses living in the U.S. The participants were asked to complete a self-administered computerised test to measure aspects of their memory and thinking. At the end of the study, it was revealed that women who took antibiotics for two months continuously in their midlife had poor memory and thinking, up to seven years later. Moreover, the effect of antibiotics remained the same, irrespective of other factors leading to cognitive declines like health conditions and lifestyle. The experts further explained that change in memory through antibiotic use was roughly equivalent to three to four years of ageing.