Table 2 Helmet use by sex.

Road type	Male			Female			Crude OR	95% CI
	n	With helmet		n	With helmet
		n	(%)		n	%
Overall helmet use
National road	4330	2594	59.91	1470	681	46.33	1.73	1.53 to 1.95
Provincial	3732	1515	40.59	1464	394	26.91	1.86	1.62 to 2.12
District	3834	1066	27.80	1240	254	20.48	1.49	1.28 to 1.75
Commune	2157	312	14.46	748	64	8.56	1.81	1.35 to 2.42
City	2957	295	9.98	1380	87	6.30	1.65	1.28 to 2.13
Total	17010	5782	33.99	6302	1480	23.48	1.68	1.57 to 1.79
					ORMH		1.69	1.61 to 1.78
Driver helmet use
National	3511	2277	64.85	407	216	53.07	1.63	1.32 to 2.02
Provincial	3047	1395	45.78	490	187	38.16	1.37	1.12 to 1.67
District	3104	991	31.93	521	150	28.79	1.16	0.94 to 1.43
Commune	1788	294	16.44	323	36	11.15	1.57	1.07 to 2.31
City	2521	264	10.47	848	50	5.90	1.87	1.35 to 2.59
Total	13971	5221	37.37	2589	639	24.68	1.82	1.65 to 2.01
					ORMH		1.64	1.53 to 1.76
Pillion passengers' helmet use
National	819	317	38.71	1063	465	43.74	0.81	0.67 to 0.98
Provincial	685	120	17.52	974	207	21.25	0.79	0.61 to 1.02
District	730	75	10.27	719	104	14.46	0.68	0.49 to 0.94
Commune	369	18	4.88	425	28	6.59	0.73	0.38 to 1.39
City	436	31	7.11	532	37	6.95	1.02	0.61 to 1.73
Total	3039	561	18.46	3713	841	22.65	0.77	0.68 to 0.87
					ORMH		0.78	0.72 to 0.85

OR_MH, Mantel–Haenszel (MH) weighted odds ratio is the summary of OR after stratification by road type.