Int. J. Epidemiol. -- Lardelli-Claret et al. 32 (1): 162 Table 1

Table 1 Crude, stratified and adjusted associations between the position on the moped, helmet use and head injury

1a Effect variable: Head injury
			Stratified analysis by helmet use
Exposure variable:	Crude analysis		Helmeted riders		Non-helmeted riders
	Head injury	Non-head injury	Head injury	Non-head injury	Head injury	Non-head injury

Position on the moped
Driver (exposed)	25 211 (15.4%)	138 112 (84.6%)	7342 (7.8%)	86 212 (92.2%)	17 869 (25.6%)	51 900 (74.4%)
Passenger (non-exposed)	3537 (14.7%)	20 493 85.3%)	485 (5.7%)	7971 (94.3%)	3052 (19.6)	12 522 (80.4%)
	OR = 1.06 (1.02–1.10)		OR = 1.40 (1.27–1.54)		OR = 1.41 (1.35–1.47)		Adjusted OR^a = 1.41 (1.36–1.47)

1b Effect variable: Head injury

Stratified analysis by position on the moped

Exposure variable: Crude analysis
Drivers
Passengers

Head injury Non-head injury Head injury Non-head injury Head injury Non-head injury

Helmet use

Non-helmeted (exposed) 20 921 (24.5%) 64 422 (75.5%) 17 869 (25.6%) 51 900 (74.4%) 3052 (19.6%) 12 522 (80.4%)

Helmeted (non-exposed) 7827 (7.7%) 94 183 (92.3%) 7342 (7.8%) 86 212 (92.2%) 485 (5.7%) 7971 (94.3%)

OR = 3.91 (3.80–4.02) OR = 4.04 (3.93–4.16) OR = 4.01 (3.63–4.43) Adjusted OR^a = 4.04 (3.93–4.15)

1c. Effect variable: Helmet use

Stratified analysis by head injury

Exposure variable: Crude analysis
Head injury
Non-head injury

Helmeted Non-helmeted Helmeted Non-helmeted Helmeted Non-helmeted

Position on the moped

Driver (exposed) 93 554 (57.3%) 69 769 (42.7%) 7342 (29.1%) 17 869 (70.9%) 86 212 (62.4%) 51 900 (37.6%)

Passenger (non-exposed) 8456 (35.2%) 15 574 (64.8%) 485 (13.7%) 3052 (86.3%) 7971 (38.9%) 12 522 (61.1%)

OR = 2.47 (2.40–2.54) OR = 2.59 (2.34–2.86) OR = 2.61 (2.53–2.69) Adjusted OR^a = 2.61 (2.53–2.68)

^aOdds ratio (95% CI in parentheses).

Percentages are referred to the totals of exposed and non-exposed riders (by rows).