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Table 3 Incidence rate ratios by ages 1–4 and 5–9 years

From: Use of hospital-based health care services among children aged 1 through 9 years who were born very preterm - a population-based study

  Age 1–4 Age 5–9
  (n = 4301) (n = 3137)
Hospital admissions IRR S.E. P** z 95%CI IRR S.E. P** z 95%CI
 Boy (vs girl) 1.22 0.10 0.014 2.47 1.04–1.44 1.38 0.19 0.017 2.38 1.06–1.80
 22–24 weeks GA (vs 31+) 2.60 0.58 <0.001 4.28 1.68–4.03 2.34 0.75 0.008 2.67 1.25–4.37
 25–26 weeks GA (vs 31+) 1.79 0.25 <0.001 4.22 1.37–2.35 1.52 0.35 0.070 1.81 0.97–2.39
 27–28 weeks GA (vs 31+) 1.38 0.16 0.007 2.69 1.09–1.74 1.51 0.31 0.046 1.99 1.01–2.27
 29–30 weeks GA (vs 31+) 1.41 0.15 0.002 3.15 1.14–1.74 1.04 0.21 0.836 0.21 0.70–1.54
 Small weight for GA (vs non-SWGA) 1.87 0.17 <0.001 6.84 1.56–2.24 1.15 0.18 0.384 0.87 0.84–1.57
 Malformation at birth (vs absence) 2.16 0.19 <0.001 8.52 1.81–2.57 1.55 0.22 0.002 3.04 1.17–2.05
 Apgar score at 5 min (difference from score 9)* 0.93 0.02 0.001 −3.40 0.89–0.97 0.94 0.05 0.187 −1.32 0.85–1.03
 Parous (vs non-parous) 1.18 0.10 0.056 1.91 1.00–1.40 0.76 0.11 0.053 −1.93 0.58–1.00
 Age of mother at birth (per 5 years from avg.)* 0.91 0.03 0.010 −2.56 0.85–0.98 1.03 0.06 0.579 0.55 0.92–1.16
 Bleeding any time in pregnancy (vs none) 1.31 0.14 0.012 2.51 1.06–1.63 1.11 0.21 0.581 0.55 0.76–1.62
 Any previous abortion up to 23rd week (vs none) 1.27 0.12 0.010 2.58 1.06–1.52 1.12 0.17 0.450 0.75 0.83–1.51
 University education grandparents (vs < university) 1.12 0.11 0.259 1.13 0.92–1.36 0.72 0.12 0.042 −2.03 0.53–0.99
 Mother is immigrant (vs native) 0.99 0.11 0.907 −0.12 0.79–1.23 0.97 0.18 0.882 −0.15 0.68–1.40
 Single/separated/divorced (vs cohabiting/married) 0.84 0.11 0.176 −1.35 0.66–1.08 0.54 0.21 0.103 −1.63 0.25–1.13
 Travel time hospital at birth (per 30 min from avg.)* 1.02 0.05 0.713 0.37 0.93–1.11 1.02 0.06 0.723 0.36 0.91–1.14
 Western health authority (vs South-Eastern) 0.73 0.08 0.002 −3.08 0.59–0.89 0.95 0.19 0.807 −0.24 0.64–1.41
 Central health authority (vs South-Eastern) 0.94 0.10 0.603 −0.52 0.76–1.17 1.10 0.22 0.642 0.46 0.74–1.62
 Northern health authority (vs South-Eastern) 0.82 0.11 0.157 −1.42 0.62–1.08 1.72 0.37 0.011 2.54 1.13–2.62
 Reference* rate per 1000 children per year 181 44 <0.001 21 112–293 60 22 <0.001 11 29–123
Outpatient visits IRR S.E. P** z 95%CI IRR S.E P** z 95%CI
 Boy (vs girl) 1.15 0.06 0.015 2.43 1.03–1.28 1.28 0.10 0.001 3.34 1.11–1.48
 22–24 weeks GA (vs 31+) 3.12 0.44 <0.001 8.16 2.37–4.10 3.13 0.52 <0.001 6.82 2.26–4.35
 25–26 weeks GA (vs 31+) 1.89 0.18 <0.001 6.72 1.57–2.27 2.05 0.27 <0.001 5.52 1.59–2.65
 27–28 weeks GA (vs 31+) 1.68 0.14 <0.001 6.16 1.42–1.98 1.79 0.19 <0.001 5.43 1.45–2.20
 29–30 weeks GA (vs 31+) 1.34 0.11 <0.001 3.65 1.15–1.57 1.31 0.14 0.011 2.54 1.06–1.62
 Small weight for GA (vs non-SWGA) 1.50 0.09 <0.001 6.59 1.33–1.69 1.28 0.10 0.002 3.08 1.09–1.50
 Malformation at birth (vs absence) 1.57 0.10 <0.001 7.18 1.39–1.77 1.53 0.13 <0.001 5.03 1.30–1.81
 Apgar score at 5 min (difference from score 9)* 0.93 0.01 <0.001 −4.28 0.91–0.96 0.94 0.03 0.018 −2.36 0.89–0.99
 Parous (vs non-parous) 1.02 0.06 0.793 0.26 0.90–1.15 0.93 0.08 0.348 −0.94 0.79–1.09
 Age of mother at birth (per 5 years from avg.)* 1.00 0.02 0.946 −0.07 0.95–1.05 1.05 0.04 0.131 1.51 0.98–1.13
 Bleeding any time in pregnancy (vs none) 1.04 0.08 0.598 0.53 0.89–1.22 1.01 0.12 0.924 0.10 0.80–1.27
 Any previous abortion up to 23rd week (vs none) 1.17 0.08 0.025 2.25 1.02–1.34 1.00 0.09 0.955 0.06 0.85–1.19
 University education grandparents (vs < university) 1.09 0.08 0.211 1.25 0.95–1.25 0.82 0.07 0.022 −2.28 0.69–0.97
 Mother is immigrant (vs native) 0.89 0.07 0.111 −1.59 0.76–1.03 0.94 0.11 0.587 −0.54 0.74–1.18
 Single/separated/divorced (vs cohabiting/married) 0.98 0.10 0.873 −0.16 0.81–1.20 0.76 0.10 0.042 −2.03 0.58–0.99
 Travel time hospital at birth (per 30 min from avg.)* 0.97 0.02 0.160 −1.40 0.92–1.01 0.95 0.03 0.079 −1.75 0.89–1.01
 Western health authority (vs South-Eastern) 0.92 0.06 0.227 −1.21 0.80–1.05 1.15 0.11 0.153 1.43 0.95–1.38
 Central health authority (vs South-Eastern) 1.04 0.08 0.624 0.49 0.89–1.21 1.32 0.12 0.003 3.00 1.10–1.59
 Northern health authority (vs South-Eastern) 0.96 0.10 0.719 −0.36 0.79–1.18 1.39 0.23 0.046 1.99 1.01–1.93
 Reference rate per 1000 children per year 1133 192 <0.001 41 812–1579 502 115 <0.001 27 320–786
  1. IRR incidence rate ratio, S.E. standard error, P p-value, z z-value, CI confidence interval, avg. average, GA gestational age, SWGA small for gestational age
  2. *Continuous variables Apgar score 5 min set to median score of 9, travel time and mothers age centered to overall mean
  3. **Numbers in bold are significant at 5% level
  4. Estimates are with multiple imputation of missing values