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. Author manuscript; available in PMC: 2019 Oct 8.
Published in final edited form as: Water Res. 2018 May 23;142:289–300. doi: 10.1016/j.watres.2018.05.030

Table 4.

Risk factors for Cryptosporidium and norovirus immunoconversions: adjusted odds ratio (95% confidence interval) from multivariate models

Predictor variable Cryptosporidium GI norovirus GII noroviruses
Study phase 1 vs. phase 2 a 1.28 (0.58; 2.80) 1.04 (0.64; 1.69) 0.50 (0.32; 0.80)*
Swimming in pools b 4.92 (1.56; 15.5)* 1.50 (0.50; 4.50) 0.92 (0.31; 2.69)
Swimming in natural water bodies b 2.33 (0.35; 15.4) 0.20 (0.03; 1.14) 1.30 (0.37; 4.51)
Interaction effect of drinking non-boiled tap water and phase 1 c
 All study participants 5.40 (1.14; 25.6)* 1.06 (0.44; 2.59) 1.21 (0.50; 2.94)
 Individuals who did not have water filters at home 15.8 (1.09; 228)* 0.82 (0.24; 2.77) 1.07 (0.33; 3.44)
 Individuals who had water filters at home 2.95 (0.34; 25.4) 1.80 (0.51; 6.44) 1.68 (0.43; 6.61)
Effect of drinking non-boiled tap water in stratified analysis d
 Phase 1, all participants 2.17 (0.77; 6.13) 1.25 (0.63; 2.47) 1.52 (0.73; 3.16)
 Phase 1, individuals who did not have home water filters # 11.1 (1.23; 100)* 0.72 (0.31; 1.66) 1.67 (0.59; 4.72)
 Phase 1, individuals who had home water filters # 0.83 (0.21; 3.33) 2.13 (0.85; 5.34) 1.40 (0.48; 4.04)
 Phase 2, all participants 0.40 (0.12; 1.27) 1.24 (0.69; 2.20) 1.13 (0.70; 1.84)
 Phase 2, individuals who did not have home water filters # 0.58 (0.13; 2.52) 1.01 (0.49; 2.05) 1.74 (0.90; 3.37)
 Phase 2, individuals who had home water filters # 0.29 (0.05; 1.58) 1.29 (0.67; 2.50) 0.71 (0.36; 1.40)
a

Adjusted for sex, number of individuals in the household, age (piece-wise regression), cubic polynomial of time, highest education level of household adults, income (for Cryptosporidium only), and language spoken at home (for noroviruses only).

b

Adjusted for sex, study phase, number of individuals in the household, age (piece-wise regression), cubic polynomial of time, highest education level of household adults, income (for Cryptosporidium only), and language spoken at home (for noroviruses only).

c

Adjusted for sex, study phase, number of individuals in the household, language spoken at home, age (piece-wise regression), cubic polynomial of time, highest education level of household adults, income (for Cryptosporidium only), language spoken at home (for noroviruses only), and drinking tap water.

d

Adjusted for sex, number of individuals in the household, age (piece-wise regression), cubic polynomial of time, highest education level of household adults, income (for Cryptosporidium only), language spoken at home (for noroviruses only), and drinking tap water.

*

p < 0.05

#

Regular logistic regression models were used for these strata.