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Table 1 Characteristics of Participants

From: Association between economic status and body mass index among adolescents: a community-based cross-sectional study in Japan

  Boys (n = 1169) Girls (n = 1133)
  n or mean % or SD n or mean % or SD
Family characteristics
 Economic status
  Non-low (comfortable, somewhat comfortable, normal, somewhat difficult) 1119 (95.72) 1095 (96.65)
  Low (difficult) 50 (4.28) 38 (3.35)
 Family structure
  Both biological parents 964 (82.46) 928 (81.91)
  Single parent or stepfamily 205 (17.54) 205 (18.09)
 Family members’ smoking status (mother, father, or others)     
  None 565 (48.33) 527 (46.51)
  Yes (≥1 person) 604 (51.67) 606 (53.49)
Child characteristics
 BMI 18.92 (2.63) 19.19 (2.57)
 BMI z-score (WHO standard) −0.17 (0.68) −0.18 (0.63)
   < −2 SD 53 (4.53) 36 (3.18)
   ≥ −2 SD and < −1 SD 215 (18.39) 220 (19.42)
   ≥ −1 SD and < +1 SD 793 (67.84) 797 (70.34)
   ≥ +1 SD and < +2 SD 94 (8.04) 67 (5.91)
   ≥ +2 SD 14 (1.20) 13 (1.15)
 Grade in school
  7th 396 (33.88) 387 (34.16)
  8th 382 (32.68) 361 (31.86)
  9th 391 (33.45) 385 (33.98)
 Breakfast skipping
  No (eat breakfast daily) 1032 (88.28) 963 (85.00)
  Yes (skip breakfast ≥ 1 time per week) 137 (11.72) 170 (15.00)
 Convenience stores or fast-food outlets
   < 1 time per week 959 (82.04) 961 (84.82)
   ≥ 1 time per week 210 (17.96) 172 (15.18)
 Club activities at school
  Physical 850 (72.71) 575 (50.75)
  Non-physical 77 (6.59) 322 (28.42)
  No participation 242 (20.70) 236 (20.83)
 Activities outside of school
  Yes 398 (34.05) 466 (41.13)
  No 771 (65.95) 667 (58.87)
 Sleeping patterns
   ≥ 6 h 30 min per day (Q2–Q5) 955 (81.69) 826 (72.90)
   < 6 h 30 min per day (Q1) 214 (18.31) 307 (27.10)
 Self-rated health status
  Good (excellent, good, fair) 1084 (92.73) 1033 (91.17)
  Not good (somewhat poor or poor) 85 (7.27) 100 (8.83)
 Smoking status     
  No 1,126 (96.32) 1107 (97.71)
  Yes 43 (3.68) 26 (2.29)