Table 2 Participant characteristics and associated factors for low VA.

From: Elevated blood pressure is associated with higher prevalence of low visual acuity among adolescent males in Northeast China

Characteristics 2005 2010 2014
Males (N = 9657) Females (N = 9608) P value Males (N = 9572) Females (N = 9601) P value Males (N = 8471) Females (N = 8411) P value
Age, year 15.51 ± 1.71 15.51 ± 1.71 0.987 15.52 ± 1.70 15.52 ± 1.70 0.871 15.44 ± 1.70 15.47 ± 1.70 0.283
Urban, n (%) 4829(50.0) 4827(50.2) 0.745 4700(49.1) 4754(49.5) 0.566 4257(50.3) 4145(49.3) 0.206
BMI, kg/m2 20.06 ± 3.28 19.81 ± 2.84 <0.001 20.68 ± 3.42 20.27 ± 2.95 <0.001 21.26 ± 3.89 20.47 ± 3.21 <0.001
SBP, mm Hg 111.67 ± 12.77 105.86 ± 11.32 <0.001 113.20 ± 12.21 106.69 ± 11.32 <0.001 116.73 ± 10.91 110.42 ± 10.44 <0.001
DBP, mm Hg 70.47 ± 8.88 68.47 ± 8.28 <0.001 68.71 ± 10.64 66.98 ± 9.80 <0.001 72.91 ± 8.60 70.34 ± 8.62 <0.001
PP, mm Hg 41.20 ± 9.91 37.39 ± 8.30 <0.001 44.49 ± 11.21 39.71 ± 9.88 <0.001 43.81 ± 9.92 40.08 ± 8.34 <0.001
PP categories, n (%)
 ≤30 2125(22.0) 3234(33.7) <0.001 1429(14.9) 2627(27.4) <0.001 877(10.4) 1471(17.5) <0.001
 31–40 3990(41.3) 4241(44.1)   3282(34.3) 3738(38.9)   3579(42.3) 4173(49.6)  
 41–50 2365(24.5) 1672(17.4)   2733(28.6) 2288(23.8)   2477(29.2) 2085(24.8)  
 ≥51 1177(12.2) 461(4.8)   2128(22.2) 948(9.9)   1538(18.2) 682(8.1)  
 Sleep duration, h/day 7.30 ± 1.10# 7.23 ± 1.01# 0.015# 7.29 ± 1.06 7.25 ± 1.00 0.005 7.30 ± 1.07 7.23 ± 1.00 <0.001
 Outdoor activity time, h/day 0.93 ± 0.58# 0.82 ± 0.50# <0.001# 0.86 ± 0.56 0.72 ± 0.50 <0.001 0.96 ± 0.60 0.84 ± 0.52 <0.001
 Homework time, h/day 1.73 ± 1.02# 1.89 ± 0.99# <0.001# 1.59 ± 0.96 1.72 ± 0.96 <0.001 1.81 ± 1.02 1.99 ± 0.98 <0.001
  1. Abbreviations: VA, visual acuity; BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure. #Data available for participants who undertook questionnaire.