Lifetime intellectual function and satisfaction with life in old age: longitudinal cohort study.

What is successful ageing? Current opinion is that “cognitive vitality is essential to quality of life . . . in old age.” This depends substantially on people’s cognitive ability from early life, and on how much they decline from their cognitive peak in young adulthood. Early cognitive ability also affects physical health and even survival to old age. But surely happiness and satisfaction with life are also key indices of successful ageing. Happiness was described as “the highest good and ultimate motivation for human action”; this does not seem to be related to current cognitive ability. Cognitive level in youth and the amount of cognitive change across the lifespan are important indicators of cognitive vitality in old age. We examined a unique data set to investigate whether these factors are associated with people being happier.