Incidence refers to the number of new cases identified in a specific time period.
Prevalence refers to the number of individuals who are living with TBI in a given time period.
Worldwide, in 2016, there were approximately 27 million new cases of TBI with an age-adjusted incidence rate of 369 per 100,000—representing a 3.6% increase from 1990. In the same year, prevalence was 55.5 million individuals, representing an 8.4% increase from 1990 (Global Burden of Disease [GBD], 2019). Each year, the number of new cases of TBI in the Unites States is approximately 2.8 million (CDC, 2015). These incidence rates include approximately 2.5 million TBI-related emergency department visits, 288,000 TBI-related hospitalizations, and 57,000 TBI-related deaths. Whereas age-adjusted rates of TBI-related ED visits increased by 54% over the span of 8 years (2006–2014), hospitalization rates decreased by 8% and death rates decreased by 6% (CDC, 2014).
According to the National Center for Injury Prevention and Control, an estimated cumulative 5.3 million individuals are living with a TBI-related disability in the United States. This represents a prevalence of approximately 2% of the U.S. population (CDC, 2015). Additional data suggest the prevalence of U.S. TBI-related disability after hospitalization to be 3.2 million (Zaloshnja, Miller, Langlois, & Selassie, 2008). Current studies estimate that approximately 775,000 older adults live with long-term disability associated with TBI (Zaloshnja et al., 2008).
Incidence and prevalence rates of TBI vary across clinical and epidemiological studies. These variations are often due to differences in participant characteristics (e.g., ages included), diagnostic classification criteria within and across subtypes (e.g., mild TBI vs. severe TBI), and sources of data (e.g., hospital admissions, emergency room visits, general practitioner visits). Moreover, current statistics do not consider individuals who do not seek medical care. Therefore, these estimates may significantly underestimate the incidence and prevalence of TBI.
The TBI prevalence in the general population is 16.7% among males and 8.5% among females. The odds of sustaining a TBI are 2.22 times higher in men than in women (Frost, Farrer, Primosch, & Hedges, 2012). Overall, males account for approximately 59% of all reported TBI-related medical visits in the United States (Faul, Xu, Wald, & Coronado, 2010).
As many as 75% of individuals who experience a TBI are diagnosed with mild TBI. This is likely an underestimate of the problem, as patients with mild TBI—who are often treated outside the hospital setting or are not treated at all—are not included in most estimates. In addition, this number includes only mild TBIs in the civilian population (CDC, 2003). It is believed that factors such as automobile safety, seatbelt use, helmet use, and better overall treatment for severe TBI in prehospital and hospital settings, while unable to prevent TBIs entirely, have mitigated the severity and thus mortality (Thurman et al., 1999).