Fig. 4.

Causal mediation analyses performed in cognitively unimpaired elderly subjects. Direct effects in filled arrows (simple regressions between variables) are expressed as standardized regression coefficients, and indirect effects in dotted arrows (multiple regressions in which the predictor and the mediator are both added in the model) as partial correlation coefficients. *P < .05, **P < .01, ***P < .001. Abbreviations: FDG, ¹⁸F-fluorodeoxyglucose; NS, nonsignificant; SF, sleep fragmentation.