Table 5.

Results of hierarchical logistic regression models.

Dependent variable = non-fatal events
Step	Variables	Odds ratio	95% CI of B	WALD	X 2	R 2	ΔR2
Demographic factors
1	Age	1.151**	1.109–1.195	54.651	58.469**	0.029	N/A
	Sex	1.102	0.939–1.294	1.422
	Parents' highest education	1.027	0.956–1.103	0.535
	Family income	1.005	0.927–1.091	0.018
Swimming experience
2	Years of swimming	0.997	0.963–1.031	0.040	58.568**	0.029	–
	Frequency of swimming	1.001	0.980–1.022	0.011
	Swimming duration	1.000	0.997–1.003	0.018
	Winter swimming	1.000	0.821–1,219	0.000
Swimming competence
3	General	1.000	0.999–1.000	0.213	11.433	0.034	0.005
	Breaststroke	1.000	0.999–1.000	0.427
	Front-crawl	1.000	0.999–1.001	0.330
	Backstroke	1.000	0.999–1.001	0.143
	Butterfly	1.000	0.998–1.001	0.352
	Swimming underwater	1.215	0.922–1.602	1.908
	Floating	1.114	0.816–1.522	0.465
	Poolside kicking	1.541	0.872–2.724	2.212
	Kickboard kicking	1.133	0.773–1.661	0.410
	Holding breath underwater	0.816	0.538–1.238	0.917
	Treading water	0.905	0.628–1.303	0.289
Swimming location
3	Public swimming pool	1.082	0.874–1.339	0.527	64.141**	0.032	0.003
	School swimming pool	1.257	0.651–2.430	0.465
	Club swimming pool	1.186	0.940–1.496	2.074
	Estate swimming pool	0.943	0.796–1.117	0.465
	Beach	1.108	0.876–1.401	0.735
Swimming accessibility
3	Public swimming pool	1.029	0.764–1.384	0.035	62.323**	0.031	0.002
	School swimming pool	1.264	0.597–2.678	0.375
	Club swimming pool	1.137	0.929–1.390	1.551
	Estate swimming pool	0.925	0.782–1.095	0.815
	Beach	1.050	0.866–1.272	0.244
Learning experience
3	Learning experience	0.996	0.945–1.049	0.027	59.267**	0.030	0.001

Controls are age, gender, grade, parents' education, income and years, frequency, duration of swimming, and winter swimming. Steps 1 and 2 were identical throughout the three models. R2, Nagelkerke R-squared. 95% CI of EXP (B), 95% confidence interval of the odds ratio. Learning experience, “Learn swimming from whom?”. PE teacher, physical education teacher. **p <0.01; N/A - not applicable.