Cycling: Greater risk of ICH vs other sports, helmets provide significant protection

A multicentre study of hospitalized patients with sports- and recreational cycling–related traumatic brain injury (TBI) in Hong Kong finds cycling-related injuries carry greater risks of unfavourable outcomes and intracranial haemorrhage (ICH) vs other sports, with helmets providing significant protection against the latter.

“With a fatality rate of 34 per billion minutes cycled [vs 3 in Stockholm, Sweden, 8 in Los Angeles and 18 in New York City, US], Hong Kong is one of the most dangerous areas in the world for cycling, yet studies reviewing outcome predictors of recreational cycling– and sports-related TBI have been sparse, thus hindering the generation of meaningful conclusions to guide governmental policy initiatives,” wrote the researchers. [PLoS One 2019;14:e0220785]

In the current study, researchers analyzed data from patients who required inpatient care at any Hospital Authority institution for sports-related TBI from 1 January 2015 to 31 December 2019. The primary outcome was presence of ICH on the admitting CT scan. The secondary outcome was unfavourable functional performance, defined as a Glasgow Outcome Scale (GOS) score of 3–5 on discharge from the hospital (3, severe disability; 4, persistent vegetative state; and 5, death). [Hong Kong Med J 2021;27:338-349]

The most common sport associated with TBI was cycling (59.2 percent), followed by football (21.3 percent) and basketball (7.5 percent). “The crude incidence of recreational cycling–related TBI requiring hospitalization was 1.1 per 100,000 population,” reported the researchers. “Compared with patients who sustained TBI when engaging in other sports, cyclists were significantly older [mean age, 26 years vs 35 years; p<0.001], with a significantly higher proportion of females vs other sports [28.2 percent vs 10.9 percent; p<0.001].”

Of cyclists admitted for head injury, 201 (47.2 percent) had ICH, which was radiologically more extensive vs non-cyclists (p<0.01). As a consequence, a greater proportion of cyclists had a worse GOS score on discharge from hospital (odds ratio [OR], 2.8; 95 percent confidence interval [CI], 1.3 to 6.2) and at 6 months (OR 4.7; 95 percent CI, 2.1 to 10.5). “The cause of death for all cyclists with 30-day mortality was severe TBI with medically refractory intracranial hypertension,” added the researchers.

“At the time of injury, 361 cyclists [84.7 percent] had not been wearing a helmet. Among eight patients [1.9 percent] who subsequently died, none had been wearing protective head gear. In univariate analysis, helmet wearing was protective against ICH,” wrote the researchers. “While helmet wearing did not reduce TBI severity according to our broadly predefined categories, among hospitalized recreational cyclists with mild head injury, helmets did provide significant protection against ICH, including potentially life-threatening epidural acute subdural haematomas, as well as skull fractures.”

“Cycling is a safe physical activity, but further legislative measures would promote and protect the welfare of individuals enjoying this sport,” concluded the researchers. Yet such laws are a divisive issue among public health experts and interest groups. According to a Hong Kong Transport Department survey (5,701 respondents) regarding attitudes towards possible helmet law and enforcement measures, the majority of respondents (78–90 percent) were in favour of introducing such legislation, especially when riding on carriageways. However, 23 percent of those who knew how to ride a bicycle (3,933 respondents) declared they would ride less frequently if mandatory helmet wearing was required. [Transport Department, Hong Kong SAR Government, Travel Characteristics Survey 2011 Final Report: https://www.td.gov.hk/filemanager/en/content_4652/tcs2011_eng.pdf]