English-Chinese/The sleep cycle of alternate NREM and REM sleep takes an average of 90 minutes, occurring 4–6 times in a good night's sleep

The sleep cycle of alternate NREM and REM sleep takes an average of 90 minutes, occurring 4–6 times in a good night's sleep.

交替的NREM和REM睡眠的睡眠周期平均需要90分钟，在良好的睡眠中发生4-6次.