Cycling is associated with many health benefits, but also with the risk of injury. Trends in bicycle-related injuries are difficult to assess because the majority of nonfatal injuries sustained while cycling are not reported to police and thus are not included in traffic statistics.1 We sought to evaluate trends in adult cycling injuries and hospital admissions in the United States using emergency department data.
Methods
The National Electronic Injury Surveillance System (NEISS) is a national probability sample of approximately 100 emergency departments that gathers product-related injury data.2 We queried the NEISS for injuries associated with bicycles (codes 5033 and 5040) from 1998 to 2013. The University of California, San Francisco, institutional review board gave the study exempt status.
The number of bicycle-related injuries in adults aged 18 years or older was recorded in 2-year intervals. We used the NEISS complex sample design to calculate population projections of cycling-related injuries, which were then divided by US Census data to produce incidence per 100 000 persons. Adjustment for age was performed using the direct method. Linear regression was used to evaluate trends in injuries and hospital admissions vs time (2-year intervals) for the entire sample as well as for the proportion of injuries by specific age groups. We also calculated the ratio of injuries by body part, location (street vs nonstreet), and hospital size.
Hospital size was used as a proxy for urban vs rural location given large hospitals were located in urban areas in the NEISS database. Statistical analysis was performed using R version 3.1.1 (R Project for Statistical Computing). P values <.05 (2-sided) were considered significant.
Results
Trends in the incidence of injuries and hospital admissions are summarized in Table 1. During the study period, the 2-year age-adjusted incidence of injuries increased by 28% from 96 (95% CI, 84–108) to 123 (95% CI, 110–136) per 100 000 (P = .02) and the 2-year age-adjusted incidence of hospital admissions increased by 120% from 5.1 (95% CI, 2.4–7.8) to 11.2 (95% CI, 7.6–14.9) per 100 000 (P = .001).
Table 1.
Trends in Number and Type of Bicycle Injury and in Hospital Admissions From 1998 to 2013
| 1998–1999 | 2000–2001 | 2002–2003 | 2004–2005 | 2006–2007 | 2008–2009 | 2010–2011 | 2012–2013 | % Changea |
P Valueb |
|
|---|---|---|---|---|---|---|---|---|---|---|
| No. of injury casesc | 8791 | 9775 | 9633 | 10 068 | 11 133 | 13 046 | 14 322 | 15 427 | ||
| Age-adjusted incidenced |
96 (84–108) |
99 (87–110) |
90 (79–101) |
89 (78–99) |
96 (85–108) |
107 (95–119) |
114 (102–126) |
123 (110–136) |
28 | .02 |
| No. of hospital admissionsc |
553 | 629 | 707 | 833 | 966 | 1239 | 1377 | 1646 | ||
| Age-adjusted incidenced |
5.1 (2.4–7.8) |
4.8 (2.4–7.3) |
4.9 (2.6–7.3) |
5.7 (3.2–8.1) |
6.1 (3.5–8.7) |
7.8 (4.9–10.8) |
9.1 (6.0–12.2) |
11.2 (7.6–14.9) |
120 | .001 |
| Type of injury, % (95% CI) |
||||||||||
| Head | 10 (6–14) |
10 (5–14) |
10 (6–15) |
12 (7–16) |
12 (7–16) |
14 (9–19) |
15 (10–19) |
16 (9–21) |
60 | <.001 |
| Torso | 14 (10–18) |
14 (10–18) |
14 (10–18) |
15 (11–19) |
16 (11–20) |
16 (12–20) |
17 (12–22) |
17 (12–22) |
20 | <.001 |
| Extremity | 59 (46–72) |
60 (45–74) |
59 (43–71) |
57 (41–70) |
56 (41–70) |
55 (41–70) |
53 (40–67) |
52 (37–66) |
−12 | <.001 |
| Other body part | 17 (11–23) |
17 (12–22) |
17 (11–22) |
16 (11–22) |
15 (11–22) |
15 (11–21) |
15 (10–20) |
16 (10–20) |
−9 | .004 |
| Location (street), % (95% CI) |
40 (18–62) |
43 (23–63) |
49 (30–67) |
55 (33–77) |
53 (30–76) |
52 (31–74) |
54 (32–75) |
56 (30–82) |
40 | .005 |
| Large hospital, % (95% CI)e |
53 (35–71) |
51 (29–73) |
50 (31–69) |
51 (31–72) |
49 (27–70) |
50 (31–69) |
53 (34–73) |
57 (32–82) |
8 | .31 |
Indicates change from 1998–1999 to 2012–2013; calculated as: [(value for 2012–2013 − value for 1998/1999)/(value for 1998–1999)] × 100.
Calculated using linear regression for each parameter compared with period in 2-year increments (eg, injuries vs time).
Counts from the National Electronic Injury Surveillance System (NEISS) database for adults aged 18 years or older in 2-year intervals.
Adjustment for age performed using the direct method. Incidence expressed as a population estimate of injured cyclists per 100 000 persons in the US population (95%CI).
Defined as hospitals in the large or very large strata in the NEISS database.
When evaluated by injury type, the percentage of injured cyclists with head injuries increased from 10% (95% CI, 6%–14%) to 16%(95% CI, 9%–21%) (P < .001) and torso injuries increased from 14% (95% CI, 10%–18%) to 17% (95% CI, 12%–22%) (P < .001). The percentage of injuries occurring on the street increased over time from40%(95% CI, 18%–62%) to 56% (95% CI, 30%–82%) (P = .005).
There was no significant change in the proportion of injured patients presenting to large hospitals. Overall, 35% of injuries occurred in women and there was no significant change in sex ratio over time.
Changes in the proportion of injuries occurring within specific age groups are summarized in Table 2. The proportion of injuries occurring in individuals older than 45 years increased 81% from 23% (95% CI, 20%–26%) to 42% (95% CI, 39%–45%) (P < .001) and the proportion of hospital admissions in individuals older than 45 years increased 66% from 39% (95% CI, 25%–53%) to 65%(95% CI, 55%–75%) (P < .001).
Table 2.
Proportion of Bicycle Injuries and Hospital Admissions by Age Group From 1998 to 2013
| Age Group, y | % (95% CI) | % Changea |
P Valueb |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1998–1999 | 2000–2001 | 2002–2003 | 2004–2005 | 2006–2007 | 2008–2009 | 2010–2011 | 2012–2013 | |||
| 18–24 | ||||||||||
| Injuries | 25 (24–26) | 24 (23–25) | 22 (21–23) | 23 (22–24) | 22 (21–24) | 23 (22–24) | 23 (22–24) | 22 (21–22) | −12 | .02 |
| Hospital admissions |
12 (9–16) | 14 (10–18) | 10 (7–12) | 8 (6–11) | 12 (9–15) | 11 (9–13) | 9 (7–11) | 12 (10–14) | 0 | .52 |
| 25–34 | ||||||||||
| Injuries | 28 (27–29) | 25 (24–26) | 23 (22–25) | 21 (20–22) | 20 (19–21) | 20 (19–21) | 20 (20–21) | 20 (19–21) | −27 | .004 |
| Hospital admissions |
20 (15–25) | 16 (13–20) | 17 (13–21) | 17 (14–21) | 14 (11–16) | 12 (9–14) | 14 (11–16) | 12 (10–14) | −41 | .004 |
| 35–44 | ||||||||||
| Injuries | 25 (23–26) | 24 (23–25) | 25 (24–26) | 23 (22–24) | 21 (20–23) | 20 (19–21) | 18 (17–18) | 17 (16–18) | −32 | <.001 |
| Hospital admissions |
29 (23–35) | 27 (22–32) | 19 (15–23) | 16 (13–19) | 15 (12–18) | 14 (12–17) | 12 (11–16) | 12 (10–14) | −60 | .001 |
| 45–54 | ||||||||||
| Injuries | 12 (11–13) | 15 (14–15) | 17 (16–18) | 19 (18–20) | 20 (19–21) | 21 (20–22) | 20 (20–21) | 21 (20–22) | 77 | .001 |
| Hospital admissions |
13 (9–16) | 20 (15–25) | 23 (19–28) | 32 (27–38) | 25 (21–30) | 23 (19–27) | 28 (24–32) | 25 (22–28) | 96 | .12 |
| 55–64 | ||||||||||
| Injuries | 6 (5–7) | 8 (7–8) | 8 (7–9) | 8 (7–9) | 10 (9–11) | 11 (10–12) | 12 (11–13) | 14 (13–15) | 130 | <.001 |
| Hospital admissions |
13 (9–17) | 12 (8–16) | 13 (10–17) | 12 (9–15) | 20 (16–24) | 22 (18–26) | 19 (16–22) | 23 (20–26) | 78 | .005 |
| 65–74 | ||||||||||
| Injuries | 4.2 (3.7–4.8) |
3.8 (3.4–4.3) |
3.9 (3.4–4.4) |
4.9 (4.3–5.4) |
5.0 (4.4–5.5) |
5.0 (4.5–5.5) |
5.5 (5.0–6.0) |
5.5 (5.0–6.0) |
30 | .002 |
| Hospital admissions |
5.9 (3.3–8.6) |
5.7 (3.2–8.3) |
8.0 (5.1–11.0) |
6.6 (4.4–8.8) |
9.0 (5.8–11.0) |
10.4 (7.7–13.0) |
12.4 (9.9–15.0) |
9.2 (7.2–11.0) |
56 | .01 |
| ≥75 | ||||||||||
| Injuries | 0.9 (0.4–1.3) |
0.9 (0.4–1.3) |
1.2 (0.7–1.7) |
1.0 (0.6–1.5) |
1.4 (0.9–1.9) |
1.4 (1.0–1.9) |
1.3 (0.9–1.7) |
1.3 (0.9–1.7) |
50 | .02 |
| Hospital admissions |
7.2 (3.8–11.0) |
5.1 (2.3–7.9) |
9.7 (6.0–13.0) |
7.7 (4.4–11.0) |
6.0 (3.4–8.7) |
8.3 (5.3–11.0) |
6.0 (3.8–8.1) |
7.6 (5.3–9.8) |
6 | .94 |
Indicates change from 1998–1999 to 2012–2013; calculated as: [(value for 2012–2013 − value for 1998/1999)/(value for 1998–1999)] × 100.
Determined using linear regression (percentage vs period in 2-year increments).
Discussion
This study reports an increase in bicycle-related injuries and hospital admissions in adults in the United States between 1998 and 2013. The increase in overall injuries was driven by an increase in injuries in individuals older than45 years. The increase in hospital admissions outpaced the increase in overall injuries, perhaps due to an increase in severe injuries in older individuals,3 who made up a greater proportion of injured cyclists in 2012–2013 compared with 1998–1999. These injury trends likely reflect the trends in overall bicycle ridership in the United States in which multiple sources show an increase in ridership in adults older than 45 years.4,5
Other possible factors contributing to the increase in overall injuries and hospital admissions include an increase in street accidents4 and an increase in sport cycling associated with faster speeds.6 As the population of cyclists in the United States shifts to an older demographic, further investments in infrastructure and promotion of safe riding practices are needed to protect bicyclists from injury.
Limitations include the use of a public health surveillance database that lacks granular data on specific causes of injury, use of protective equipment (eg, helmets), and specific diagnoses (International Classification of Diseases codes).
Acknowledgments
Funding/Support: Dr Breyer is supported by grant K12DK083021 from the National Institute of Diabetes and Digestive and Kidney Diseases. Dr Callcut is supported by grant 8KL2TR000143-09 from the National Institutes of Health.
Role of the Funder/Sponsor: The National Institute of Diabetes and Digestive and Kidney Diseases and the National Institutes of Health had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: We thank Thomas Schroeder, MS, from the National Electronic Injury Surveillance System (NEISS) for his assistance with the current NEISS sample; no compensation was received.
Footnotes
Author Contributions: Drs Sanford and Breyer had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Sanford, Carroll, Breyer.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Sanford, Breyer.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Sanford, McCulloch, Breyer.
Obtained funding: Breyer.
Administrative, technical, or material support: Callcut, Carroll, Breyer.
Study supervision: Breyer.
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Breyer reported serving on an advisory board for American Medical Systems. No other disclosures were reported.
References
- 1.Lopez DS, Sunjaya DB, Chan S, Dobbins S, Dicker RA. Using trauma center data to identify missed bicycle injuries and their associated costs. J Trauma Acute Care Surg. 2012;73(6):1602–1606. doi: 10.1097/TA.0b013e318265fc04. [DOI] [PubMed] [Google Scholar]
- 2.Division of Hazard and Injury Data Systems, US Consumer Product Safety Commission. The National Electronic Injury Surveillance System. [Accessed January 23, 2015]; http://www.cpsc.gov//PageFiles/106626/2000d015.pdf.
- 3.Rivara FP, Thompson DC, Thompson RS. Epidemiology of bicycle injuries and risk factors for serious injury. Inj Prev. 1997;3(2):110–114. doi: 10.1136/ip.3.2.110. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Pucher J, Buehler R, Seinen M. Bicycling renaissance in North America? an update and re-appraisal of cycling trends and policies. Transp Res Part A Policy Pract. 2011;45(6):451–475. [Google Scholar]
- 5.Edmonson B. The US bicycle market: a trend overview. [Accessed June 30, 2015]; http://www.gluskintownleygroup.com/downloads/The%20US%20Bicycle%20Market%20-%20A%20Trend%20Overview%20Report.pdf. [Google Scholar]
- 6.USA Cycling and the USA Cycling Development Foundation. 2013 Annual report. [Accessed April 11, 2015]; https://s3.amazonaws.com/USACWeb/forms/media/2013-USA-Cycling-Annual-Report.pdf. [Google Scholar]