Table 3

Tobit regression models for the relationship between Cs-137 level (bq/kg) and covariates

VariablesRelative risk (95% CI)
Model 1Model 2Model 3
Radiocesium deposition (10 kbq/m2)†1.03 (1.01 to 1.05)*
 Class 1Ref.Ref.
 Class 21.31 (1.00 to 1.71)1.00 (0.69 to 1.46)
 Class 31.11 (0.81 to 1.52)1.29 (0.90 to 1.85)
 Class 41.20 (0.83 to 1.75)1.39 (0.98 to 1.97)
 Class 51.73 (1.19 to 2.53)**1.47 (1.04 to 2.07)*
Age (years)
 (16–40)Ref.Ref.Ref.
 (40–65)1.44 (0.97 to 2.14)1.44 (0.97 to 2.13)1.44 (0.97 to 2.12)
 65–2.20 (1.45 to 3.33)***2.20 (1.45 to 3.34)***2.17 (1.44 to 3.29)***
Gender
 MaleRef.Ref.Ref.
 Female0.52 (0.39 to 0.71)***0.52 (0.39 to 0.71)***0.53 (0.39 to 0.71)***
Height (cm)0.98 (0.96 to 1.00)*0.98 (0.96 to 1.00)*0.98 (0.96 to 1.00)*
Location
 Minamisoma cityRef.Ref.Ref.
 Inside Fukushima0.89 (0.58 to 1.38)0.88 (0.56 to 1.37)0.92 (0.60 to 1.43)
 Outside Fukushima0.70 (0.28 to 1.76)0.75 (0.29 to 1.90)0.79 (0.31 to 2.03)
Examination date1.00 (1.00 to 1.00)**1.00 (1.00 to 1.00)**1.00 (1.00 to 1.00)**
Season of examination
 SpringRef.Ref.Ref.
 Summer0.66 (0.52 to 0.85)**0.66 (0.51 to 0.84)**0.67 (0.52 to 0.86)**
 Autumn1.25 (0.89 to 1.76)1.25 (0.89 to 1.76)1.27 (0.90 to 1.79)
 Winter1.31 (0.82 to 2.09)1.31 (0.82 to 2.09)1.33 (0.83 to 2.12)
  • *<0.05, **<0.01, ***<0.001.

  • †Classes 1–5 indicate (0–2.5), (2.5–5.0), (5.0–7.5), (7.5–10.0) and 10.0–, respectively, for model 2, and (0–1.1), (1.1–2.8), (2.8–4.3), (4.3–6.3) and 6.3–, respectively, for model 3.