For example, cerebral tau deposition has been associated with increased total sleep time observed in cognitively unimpaired adults and patients with Alzheimer’s disease.62,63 Hence, whilst initial shorter total sleep duration may be cross-sectionally associated with higher CSF tau, its cerebral deposition could contribute to the opposite clinical effect, nullifying longitudinal relationships. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.