Fig. 3

Comparisons of NPTR and Fitbit parameters in two groups between first night and second night. A NPTR parameters of the first night in Group A and Group B; B NPTR parameters of the second night in Group A and Group B; C Fitbit parameters of the first night in Group A and Group B; D Fitbit parameters of the second night in Group A and Group B. NPTR: nocturnal penile tumescence and rigidity; TTT: total test time; EEE: effective erectile events; TET: total erection time; D60%: duration of erectile episodes with rigidity ≥ 60%; AER: average event rigidity; TST: total sleep time; SOL: sleep onset latency; WASO: wake after sleep onset; REM: rapid eye movement; Group A and Group B were the two groups based on the NPTR results; N1 and N2 were the first night and the second night for participants’ examination; Differences between Group A and Group B within the first night and the second night were assessed by independent t tests; *: P < 0.05 when measurement on Group A was compared with that on Group B; ns: P > 0.05 when measurement on Group A was compared with that on Group B