AGING AND COGNITION - METHODOLOGICAL DIFFERENCES IN OUTCOME

A series of longitudinal and cross sectional studies, collected as par t of the Seattle Study, were reanalyzed. A longitudinal sequential ana lysis (N = 232), wherein subjects were measured every seven years for four time periods, was completed on the Primary Mental Abilities test. Cohort differences were at least as strong as age differences; cohort s were generally relatively stable over the measured periods, showing little cognitive decline. A cross-sectional sequential analysis (N = 2 813) was completed for the same time periods, decline with age was mor e evident than with the longitudinal sequential analysis. A cross-sect ional analysis for the fourth time period (N = 611) showed the most ma rked decline of all. interpretation of outcome was highly dependent on the analysis used.