Wednesday, September 09, 2015

Old farts on bikes

From a Chronicle story (Study: Injury rates for older cyclists skyrocket over past 15 years) about the latest UC study on bicycle injuries. (The study itself is below in italics, emphasis added, tables omitted):

While bicycling certainly has its health benefits, a new study on injury rates over the past 15 years is proving that riding a bike can be risky — especially for older cyclists.

The study, conducted by researchers at UCSF and published in the September issue of the Journal of the American Medical Association, found that hospital admissions associated with bicycle injuries more than doubled between 1998 and 2013, with head and torso injuries occurring most frequently.

For riders over the age of 45, the proportion of injuries rose by 81 percent during that time, the authors wrote. Older riders who got hurt were more likely to need further care as well, with the proportion of them being admitted to hospitals jumping from 39 to 65 percent.

“These injuries were not only bad enough to bring riders to the emergency room, but the patients had to be admitted for further care,” said Benjamin Breyer, senior author of the study and chief of urology at San Francisco General Hospital. “If you take typical 25-year-olds and 60-year-olds, if they have a similar crash, it’s more likely the older person will have more severe injuries"...

Bicycle Trauma Injuries and Hospital Admissions in the United States, 1998-2013

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). 

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 from 40% (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).

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 than 45 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 accidents 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).

Thomas Sanford, MD
Charles E. McCulloch, PhD
Rachael A. Callcut
Peter R. Carroll, MD, MPH
Benjamin N. Breyer, MD, MAS

Author Affiliations: Department of Urology, University of California, San Francisco (Sanford, Carroll, Breyer); Department of Epidemiology and Biostatistics, University of California, San Francisco (McCulloch); Department of Surgery, University of California, San Francisco (Callcut).

Corresponding Author: Benjamin N. Breyer, MD, MAS, Department of Urology, University of California, San Francisco General Hospital, 1001 Potrero Ave, San Francisco, CA 94110 (

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.

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.

2. Division of Hazard and Injury Data Systems, US Consumer Product Safety Commission. The National Electronic Injury Surveillance System. Accessed January 23, 2015.

3. Rivara FP, Thompson DC, Thompson RS. Epidemiology of bicycle injuries and risk factors for serious injury. Inj Prev. 1997;3(2):110-114.

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.

5. Edmonson B. The US bicycle market: a trend overview. Accessed June 30, 2015.

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