“…To our knowledge, there is only one study showing that male mice have an overall shorter resting period than females ( Franken et al, 2006 ), and another in rats showing less NREMS in males when compared to females in the estrus phase ( Kostin et al, 2020 ). An absence of sex difference in time spent in NREMS in mice was reported by one study using a piezoelectric assessment of sleep (no EEG quantification; Wang et al, 2020 ), two studies underpowered to assess sex differences (e.g., n = 3 males) ( Brankack et al, 2010 ; Hellman et al, 2010 ), and two other studies not designed to primarily investigate sex differences ( Grønli et al, 2016 ; Huitron-Resendiz et al, 2018 ). In contrast, we found seven studies having shown that male mice and rats spend more time in NREMS than females ( Ehlen et al, 2013 ; Franken et al, 2006 ; Koehl et al, 2006 ; Nichols et al, 2020 ; Paul et al, 2006 ; Saré et al, 2020 ; Swift et al, 2020 ).…”