Table 2 Independent variables and dependent variables for regression models. The ‘Missing’ column indicates the percentage of values that were missing and were imputed.

From: Statistical Modeling of Heart Rate Variability to Unravel the Factors Affecting Autonomic Regulation in Preterm Infants

Independent variables Data type Median (IQR) Missing (%)
Gender Categorical Male: 45% KCs 0
Gender of the parent performing KC Categorical Mother: 61% KCs 3.8
Gestational age (GA), day Numerical 197 (188–209) 0
   GA ≤ 28 weeks (48% of KCs) Numerical 188 (177.5–189) 0
   GA > 28 weeks (52% of KCs) Numerical 208 (201–213) 0
Postmenstrual age, day Numerical 218 (209–226) 0
Birth weight (BW), g Numerical 1030 (830–1275) 0
   ELBW (<1000 g), (49% of KCs) Numerical 830 (680–935) 0
   VLBW (1000–1500 g), (44% of KCs) Numerical 1275 (1120–1330) 0
   LBW (1500–2499 g), (7% of KCs) Numerical 1765 (1640–1860) 0
Duration of KC, min Numerical 100 (81–120) 0
Heart rate (bpm) Pre-KC Numerical 160.4 (153.4–167.4) 0.1
During-KC Numerical 159.5 (153.3–165.3) 0.3
Breathing rate (brpm) Pre-KC Numerical 52.35 (45.6–60.6) 1.6
During-KC Numerical 49.5 (43.1–57.1) 1.5
Dependent variables Data type Median (IQR) Missing (%)
SDNN (ms) Pre-KC Numerical 24.33 (24.05–24.70) 0
During KC Numerical 21 (20.7–21.7) 0
pDec (%) Pre-KC Numerical 46.47 (46.36–46.74) 0
During KC Numerical 45.80 (45.25–46.72) 0
SDDec (ms) Pre-KC Numerical 24.38 (23.96–25.05) 0
During KC Numerical 22.14 (21.61–22.97) 0
  1. Abbreviations: KC, Kangaroo care; KCs, Kangaroo care sessions; IQR, interquartile range; GA, gestational age; bpm, beats per minute; brpm, breaths per minute; BW, birth weight; SDNN, standard deviation of normal to normal intervals; pDec, percentage of decelerations; SDDec, standard deviation of decelerations.