Fig. 2

Comparisons of NPTR and Fitbit parameters in two nights between Group A and Group B. A NPTR parameters of Group A in two nights; B NPTR parameters of Group B in two nights; C Fitbit parameters of Group A in two nights; D Fitbit parameters of Group B in two nights. NPTR: Nocturnal Penile Tumescence and Rigidity; Fitbit: Fitbit Charge 2™; 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 the first night and the second night within Group A and Group B were assessed by paired sample t tests; *: P < 0.05 when measurement on the second night was compared with that on the first night; ns: P > 0.05 when measurement on the second night was compared with that on the first night