The SMC was rated using the Memory Complaint Questionnaire (MAC-Q) [14], in the absence of delirium identified with the Confusion Assessment Method [15]. The six-item MAC-Q requires participants to compare current memory function to memory function at earlier ages in daily scenarios. Five questions address daily activities compared to 5 years ago; and one final question addresses the general feeling on overall memory function compared to 10 years ago. For each question, five possible answers range from “much better now” (scored 5) to “much worse now” (scored 1), with a total score out of 30 (best). Serious SMC was defined as MAC-Q score ≤15 (/30), as previously published [12]. The MAC-Q is easy to perform, has been validated against lengthy questionnaires, and demonstrates good internal consistency together with satisfactory test-retest reliability [14].
2.4. Covariables