Table 2.

Regression analyses for “often or very often back pain.”

Explanatory variable	Odds ratio	Standard error	z-value	P value	ΔR 2
Variables in the equation, pseudo R 2 = 2.55%
Constant	0.11	0.06	−4.48	<0.001
BMI	1.05	0.02	2.95	0.003	0.75%
Gender	0.48	0.07	−4.81	<0.001	2.09%
Terms not in the equation, value if added next
Country	1.38	0.21	2.18	0.029	0.42%
Age	1.00	0.005	0.58	0.559	0.03%
Age2	1.00	0.0003	−0.69	0.490	0.07%
BMI2	1.00	0.004	−0.16	0.874	0.00%
Country ∗ gender	0.94	0.27	−0.20	0.843	0.42%
Country ∗ age	1.00	0.01	0.05	0.963	0.42%
Country ∗ BMI	0.98	0.03	−0.53	0.597	0.44%
Gender ∗ age	1.00	0.01	−0.07	0.944	0.03%
Gender ∗ BMI	0.96	0.04	−1.18	0.237	0.12%
Age ∗ BMI	1.00	0.001	0.77	0.433	0.08%