Research frequently shows that increased life expectancy leads to declines in health and fundamental changes in the make-up of populations and the way in which societies function. With this in mind, many of us assume that the age at which we begin our decline into ‘old age’ is in our sixties. A new study from Inserm and University College London has found, however, that our cognitive decline beings much earlier than previously estimated.
The study looked at the medical records of almost 5200 men and 2200 women 
aged between 45 and 70 years who were monitored for a decade. The patients were tested for cognitive function (including memory, vocabulary, reasoning and verbal fluency) three times over the follow-up period. All of the cognitive functions, except for vocabulary, were found to decline beginning at the age of 45. As age increases, so does the rate of cognitive decline with almost a 10% reduction in test scores aged 65–70 in comparison to only 3.6% aged 45–49.
The authors of the study write that “Determining the age at which cognitive decline begins is important since… interventions… are likely to be more effective if they are applied from the onset of decline.”