Head injuries related to bicycle collisions and helmet use – an observational study

Figures & data

Figure 1. Revised STROBE chart of inclusion. STROBE: STrengthening the Reporting of OBservational studies in Epidemiology, DNPR

Table 1. Comparison of patients with head trauma according to status of head injury in patients assessed by the copenhagen emergency medical services.

	Non-head injury (n = 160)	Head injury (n = 247)	Total (n = 407)	p-Value
Age, yrs, median, [IQR]	41 [25–54]	41 [28–57]	41 [27.0–55.5]	0.326
Age group, yrs
0–15	15 (9)	15 (6)	30 (7)
16–35	53 (33)	91 (37)	144 (35)
36–55	57 (36)	74 (30)	131 (32)
56–75	29 (18)	60 (24)	89 (22)
>76	6 (4)	7 (3)	13 (3)	0.316
Sex, male	101 (63)	128 (52)	229 (56)	0.032*
Hour interval
8.01am–5pm	64 (40)	110 (45)	174 (43)	0.423
5.01 pm–12pm	59 (37)	104 (42)	163 (40)	0.342
12.01 pm–08am	37 (23)	33 (13)	70 (17)	0.016
Weekend	47 (29)	59 (24)	106 (26)	0.264
Suspected alcohol involvement	30 (19)	37 (15)	67 (17)	0.387
Level of triage
Level 1	3 (2)	6 (2)	9 (2)	0.979
Level 2	8 (5)	12 (5)	20 (5)	1.000
Level 3	24 (15)	75 (30)	99 (24)	<0.001*
Level 4	122 (76)	148 (60)	270 (66)	<0.001*
Mechanism of collision
Collision with a moving vehicle	51 (32)	106 (43)	157 (39)	0.033*
Collision with a stationary vehicle or object	33 (21)	51 (21)	84 (21)	1.000
Fall	76 (48)	85 (34)	161 (40)	0.011*

Missing data are excluded from the denominator. Summary statistics are presented as numbers (%); yrs: years; IQR: interquartile range; *significant difference.

Table 2. Reported helmet use in patients with suspected head trauma assessed by the copenhagen emergency medical services.

	No helmet reported (n = 175)	Helmet reported (n = 113)	Unknown helmet status (n = 119)	Total (n = 407)	p-Value
Age, yrs, median [IQR]	38 [26–54]	45 [31–55]	39 [25–58]	41 [27–56]	0.049*
Age group, yrs
0–15	11 (6)	11 (10)	8 (7)	30 (7)
16–35	69 (39)	27 (24)	48 (40)	144 (35)
36–55	56 (32)	48 (43)	27 (23)	131 (32)
56–75	32 (18)	24 (21)	33 (28)	89 (22)
>76	7 (4)	3 (3)	3 (3)	13 (3)	0.024*
Sex, male	85 (49)	69 (61)	75 (63)	229 (56)	0.024*
Hour interval
8.01am–5pm	69 (39)	60 (53)	45 (38)	174 (43)	0.031*
5.01 pm–12 pm	68 (39)	39 (35)	56 (47)	163 (40)	0.137
12.01 pm–8am	38 (22)	14 (12)	18 (15)	70 (17)	0.095
Weekend	48 (27)	24 (22)	34 (29)	106 (26)	0.382
Suspected alcohol involvement	36 (20)	3 (3)	28 (24)	67 (17)	<0.001*
Level of triage
Level 1	5 (3)	0 (0)	4 (3)	9 (2)	0.164
Level 2	7 (4)	5 (4)	8 (7)	20 (5)	0.548
Level 3	45 (26)	31 (27)	23 (19)	99 (24)	0.303
Level 4	115 (66)	76 (67)	79 (66)	270 (66)	0.964
Type of collision
Collision with a moving vehicle	73 (42)	38 (34)	46 (39)	157 (39)	0.388
Collision with a stationary object or vehicle	42 (24)	22 (20)	20 (17)	84 (21)	0.306
Fall	58 (33)	51 (45)	52 (44)	161 (40)	0.069

Missing data are excluded from the denominator, including unknown helmet status. Summary statistics are presented as numbers (%); yrs: years; IQR: interquartile range; *significant difference.

Table 3. Outcomes in patients with suspected head trauma according to the reported use of helmet.

	No helmet reported (n = 175)	Helmet reported (n = 113)	Unknown helmet status (n = 119)	p-Value
Head injury present	118 (67.4)	59 (52.2)	70 (58.8)	0.032*
30-Day survival	174 (99.4)	113 (100.0)	118 (99.2)	0.644
Head injury severity
Mild	51 (29.5)	32 (28.8)	31 (27.2)	0.895
Minimal	110 (63.6)	72 (64.9)	70 (61.4)	0.901
Moderate	7 (4.0)	6 (5.4)	10 (8.8)	0.772
Severe	5 (2.9)	1 (0.9)	3 (2.6)	0.409
Missing	2	2	5
Primary diagnosis
Concussion	47 (26.9)	35 (31.0)	31 (26.1)	0.504
Diffuse traumatic brain lesion	2 (1.1)	0 (0.0)	1 (0.8)	0.521
Epidural hemorrhage	2 (1.1)	1 (0.9)	0 (0.0)	1.000
Facial fracture	9 (5.1)	9 (8.0)	8 (6.7)	0.333
Facial lesion	35 (20.0)	30 (26.5)	32 (26.9)	0.198
Intracranial hemorrhage	3 (1.7)	2 (1.8)	2 (1.7)	1.000
Intracranial hemorrhage, not specified	1 (0.6)	1 (0.9)	0 (0.0)	1.000
Open scalp lesion	24 (13.7)	1 (0.9)	18 (15.1)	< 0.001*
Subarachnoidal hemorrhage	10 (5.7)	6 (5.3)	4 (3.4)	1.000
Subdural hemorrhage	2 (1.1)	3 (2.7)	0 (0.0)	0.384
Skull fracture	2 (1.1)	0 (0.0)	2 (1.7)	0.522
Superficial scalp lesion	25 (14.3)	11 (9.7)	12 (10.1)	0.279
No head or facial injury	13 (7.4)	15 (13.3)	9 (7.6)	0.190

Missing data are excluded from the denominator. Summary statistics are presented as numbers (%), *significant difference.

Figure 2. Adjusted multivariable analyses of helmet usage. OR: odds ratio.

Figure 3. Adjusted multivariable analysis according to helmet status. OR: odds ratio

Data availability statement

The data supporting this study’s findings are available from the Danish Patient Safety Authority. Still, restrictions apply to the availability of these data, which were used under license for the current research and are not publicly available. Data are, however, available from the authors upon reasonable request and with permission of the Danish Patient Safety Authority.