Table 4.

The interaction between humidity, education and altitude in predicting short stature.

Variables	WHO reference			China reference
	OR	95% CI	P	OR	95% CI	P
UNADJUSTED
Interaction between altitude and education
Altitude ≤ 400 m/Education>9 years	Reference			Reference
Altitude ≤ 400 m/Education ≤ 9 years	4.00	1.16–13.82	0.028	3.38	0.97–1.78	0.057
Altitude>400 m/Education>9 years	3.43	0.95–12.39	0.060	3.43	0.95–12.39	0.060
Altitude>400 m/Education ≤ 9 years	8.40	2.41–29.23	0.001	8.40	2.41–29.23	0.001
Interaction between education and humidity
Education>9 years/Humidity ≤ 70%	Reference			Reference
Education ≤ 9 years/Humidity ≤ 70%	1.56	0.34–7.15	0.565	1.56	0.34–7.15	0.565
Education>9 years/Humidity>70%	2.96	0.79–11.09	0.107	2.96	0.79–11.09	0.107
Education ≤ 9 years/Humidity>70%	13.89	3.72–51.81	<0.001	11.88	3.22–43.75	<0.001
MULTIVARIABLE ADJUSTED
Interaction between altitude and education
Altitude ≤ 400 m/Education>9 years	Reference			Reference
Altitude ≤ 400 m/Education ≤ 9 years	2.94	0.78–11.14	0.112	2.32	0.61–8.84	0.217
Altitude>400 m/Education>9 years	9.34	1.49–58.49	0.017	6.45	1.06–39.42	0.043
Altitude>400 m/Education ≤ 9 years	13.35	2.50–71.30	0.002	9.64	1.86–50.05	0.007
Interaction between education and humidity
Education>9 years/Humidity ≤ 70%	Reference			Reference
Education ≤ 9 years/Humidity ≤ 70%	1.37	0.28–6.71	0.699	1.33	0.27–6.64	0.729
Education>9 years/Humidity>70%	2.13	0.39–11.64	0.385	2.19	0.39–12.31	0.372
Education ≤ 9 years/Humidity>70%	7.18	1.23–41.88	0.028	6.23	1.05–36.93	0.044

WHO, World Health Organization; OR, odds ratio; 95% CI, 95% confidence interval.