[Relationship between length of sleep and oxidative stress marker, urinary 8-hydroxy-2'-deoxyguanosine]

In this study, we aim to examine whether the length of sleep modifies the level of urinary 8-hydroxy-2'-deoxyguanosine (8-OH-dG).

Subjects were 146 workers who were engaged in management, clerical work, laboratory work, or business at a certain company. We obtained information on the subjects concerning gender, body mass index, drinking and smoking habits, and the lengths of habitual and previous night sleep among others using self-reported questionnaires, which were then confirmed by interview. Urine specimens were collected in the morning and those from the second or later void were used to measure 8-OH-dG and creatinine levels. The amount of 8-OH-dG normalized by creatinine content was used as the indicator of 8-OH-dG excretion (Spot Urine 8-OH-dG: SU8-OH-dG). We excluded subjects who took sleeping pills the previous night or habitually, and those whose levels were beyond the three-standard-deviation range. The subjects were then classified into three equal-sized groups according to the length of sleep, either habitual or the previous night.

(1) A long or a short previous night's sleep, drinking alcohol more than once a week, and habitual use of medicine increased SU8-OH-dG level among female subjects. (2) A short previous night's sleep and habitual smoking, and a short previous night's sleep and habitual use of medicine had interactions which increased SU8-OH-dG level among male subjects but the length of a previous night's sleep itself did not have an effect on SU8-OH-dG level. (3) The length of habitual sleep had no effect on SU8-OH-dG level.