Table 1. Group differences in epidemiological and psychological characteristics among groups with different sleep duration.

Values are presented as mean±standard deviation or number (%), unless otherwise specified.

^*Unit is 10,000 Korean won/mo and a value of 250 was applied based on the mean of household income within the bottom 50% in 2014. ^†,^‡,^§Several data were missing (^†one, ^‡two, and ^§eleven). ^∥Unit is day/wk. ^¶Analysis of variance or ^**Chi-square test were used to measure group differences.