The Effect Modification models were defined at two points in time , early and later , and were specified by including a multiplicative interaction term between parks from the two successive time periods ( i.e. an interaction between childhood parks and adulthood parks ) ( Fig . 1 ; see Model 4a ) . These models emphasised the temporal sequence of exposure during early or later life as being important for the eventual association with cognitive ageing . As before , we compared the partial Fstatistics of each life course model with the " saturated " model . A pvalue of over 0.05 signified that the life course model fitted the data as well as the " saturated model " . The life course model with the highest pvalue was deemed the most appropriate as this meant that it not only fit the data as well as the " saturated model " , but was more parsimonious . All models were adjusted for sex in a complete - case analysis . A positive regression coefficient represented higher residualised change in cognitive function between the time points ( i.e. relatively better cognitive change ) whereas a negative regression coefficient represented decreasing residualised change in cognitive function between the time points ( i.e. relatively worse cognitive change ) . The multiplicative interaction regression coefficient was interpreted as the coefficient of one park term being conditional on another .