A reevaluation of the common factor theory of shared variance among age, sensory function, and cognitive function in older adults.

The common cause hypothesis of the relationship among age, sensory measures, and cognitive measures in very old adults was reevaluated. Both sensory function and processing speed were evaluated as mediators of the relationship between age and cognitive function. Cognitive function was a latent variable that comprised 3 factors including memory, speed, and verbal ability. The sample was population based and comprised very old adults (n = 894; mean age = 77.7, SD = 5.6 years) from the Australian Longitudinal Study of Ageing. The results showed that there was common variance in the cognitive factor shared by age, speed, vision, and hearing but that specific effects of age on cognition remained. Furthermore, speed did not fully mediate the effect of age or sensory function on cognition. Some age differences in cognitive performance are not explained by the same processes that explain age differences in sensory function and processing speed.