Firearm mortality in the USA, Mexico, Brazil, and Colombia is highest among young adult men, and is strongly associated with race and ethnicity, and low education levels. Reductions in firearm deaths would improve life expectancy, particularly for black men in the USA, and would reduce racial and educational disparities in mortality.

Between 1990 and 2015, 106·3 million medically-certified deaths were recorded, including 2 472 000 firearm deaths, of which 851 000 occurred in the USA, 272 000 in Mexico, 855 000 in Brazil, and 494 000 in Colombia. Homicides accounted for most of the firearm deaths in Mexico (225 000 [82·7%]), Colombia (463 000 [93·8%]), and Brazil (766 000 [89·5%]). Suicide accounted for more than half of all firearm deaths in the USA (479 000 [56·3%]). In each country, firearm mortality was highest among men aged 15–34 years, accounting for up to half of the total risk of death in that age group. During the study period, firearm mortality risks increased in Mexico and Brazil but decreased in the USA and Colombia, with marked national and subnational geographical variation. Young men with low educational attainment were at increased risk of firearm homicide in all four countries, and in the USA and Brazil, black and brown men, respectively, were at the highest risk. The risk of firearm homicide was 14 times higher in black men in the USA aged 25–34 years with low educational attainment than comparably-educated white men (1·52% [99% CI 1·50–1·54] vs 0·11% [0·10–0·12]), and up to four times higher than in comparably-educated men in Brazil, Colombia, and Mexico. In the USA, the risk of firearm homicide was more than 30 times higher in black men with post-secondary education than comparably educated white men. If countries could achieve the same firearm mortality rates nationally as in their lowest-burden states, 1 777 800 firearm deaths at all ages and in both sexes could be avoided, including 1 028 000 deaths in men aged 15–34 years.

In this comparative analysis of firearm mortality, we examined national vital statistics data from 1990–2015 from four publicly available data repositories in the USA, Mexico, Brazil, and Colombia. We extracted medically-certified deaths and underlying population denominators to calculate the age-specific and sex-specific firearm deaths and the risk of firearm mortality at the national and subnational level, by education for all four countries, and by race or ethnicity for the USA and Brazil. Analyses were stratified by intent (homicide, suicide, unintentional, or undetermined). We quantified avoidable mortality for each country using the lowest number of subnational age-specific and period-specific death rates.

Firearm mortality is a leading, and largely avoidable, cause of death in the USA, Mexico, Brazil, and Colombia. We aimed to assess the changes over time and demographic determinants of firearm deaths in these four countries between 1990 and 2015.

We quantified the temporal and spatial trends in firearm mortality among different subpopulations in the USA, Mexico, Brazil, and Colombia between 1990 and 2015. We selected these four countries because they have high-quality and complete cause-of-death data and high firearm mortality. We assessed national and subnational variation in overall and intent-specific firearm mortality and calculated the individual risks and population-based rates of firearm mortality by sex, age, time period, educational level, and race or ethnicity. We estimated the number of avoidable deaths from firearms in each of these groups between 1990 and 2015.

Our study highlights the substantial public health impact of firearms in the USA, Mexico, Colombia, and Brazil. The extreme variation in the risk of firearm mortality among subpopulations and the rapid fluctuations in death rates provides strong evidence of avoidability, and also of the importance of educational level and race. Changes in firearm mortality rates explain most of the reductions in overall mortality among young men in the study countries observed in the past 25 years. In the USA, firearm deaths were the main contributor to the marked differences in the overall risk of mortality between young white and black men, regardless of educational level.

In this study, we used high-quality and complete vital registration data to assess demographic determinants and patterns in firearm mortality between 1990 and 2015 in the USA, Mexico, Brazil, and Colombia, and the contribution of firearms to overall mortality, and estimated the number of avoidable firearm deaths. We focused on the racial and educational differences in risk of firearm mortality. We found that firearm mortality is a leading, and largely avoidable, cause of death in young men (aged 15–34 years) in the USA, Mexico, Brazil, and Colombia, and is the leading contributor to mortality at these ages. The risk of firearm mortality within countries is highest among young men, and is strongly associated with place of residence, race and ethnicity, and level of education. Poorly educated black men in the USA were at the highest risk of mortality of any age group, sex, ethnicity, or educational subgroup across the four countries.

Firearms are a persistent cause of death globally, and the rates of firearm mortality vary substantially between countries. We searched PubMed for articles in English, Spanish, or Portuguese published between Sept 1, 1980, and Sept 1, 2018, using the search terms “(firearm* OR gun OR guns) AND (mortality OR death*) AND ((US OR USA OR United States) OR Colombia OR Mexico OR Brazil)”. We found that geographical and demographic variation in firearm mortality within and between countries in the Americas was mostly undocumented. Furthermore, the contribution of firearm deaths to the overall mortality among different demographic groups has not been investigated. A detailed understanding of firearm mortality in the Americas is required to inform public health responses.

The comparative epidemiological and demographic determinants of firearm deaths in the Pan-American region are poorly documented, which is surprising since these events are common and attract considerable media and public attention, especially following mass shootings.Although the number of firearm deaths has been reported at the national level,the marked variation in firearm mortality in the Americas at the country level, subnational level, by race or ethnicity and education level, and the impact of these deaths on life expectancy among subpopulations, have not previously been examined.Race, place of residence, and socioeconomic opportunity might contribute to variation in the sex-specific rates of injuries and deaths from firearms between and within countries. Quantification of subnational variations could help our understanding of firearm deaths, highlight populations at risk, and identify opportunities for intervention, including reducing firearm exposure.

Firearms have remained a persistent cause of death in the Americas for the past 25 years.Firearm mortality in the USA is markedly higher than in any other high-income country,and in several Central and South American countries, firearm mortality is even higher than in the USA.Globally, firearm mortality is highest in countries in which firearms are easily accessible.

The funders of the study had no role in the study design, data collection, analysis, interpretation, or writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.

Avoidable mortality refers to deaths that could have been avoided either through individual and population level prevention measures (also referred to as preventable deaths) or deaths that could have been avoided through optimum quality health care (amenable deaths).We quantified avoidable mortality in three ways. First, we estimated firearm deaths in excess of those observed in the states of each country with the lowest age-specific firearm death rates in any 5-year time period. Second, we calculated avoidable firearm deaths among men as the excess over those observed among women of the same age group and time period. Third, we calculated firearm deaths for the whole of the USA and Brazil in excess of the death rates among white individuals, who were observed in both countries to have the lowest age-specific firearm death rates. Avoidable deaths are presented as total deaths for each country from 1990–2015.

We standardised mortality data at ages 15–34 years to a uniform age distribution by averaging the age-specific death rates at age 15–19, 20–24, 25–29, and 30–34 years. The death rate (R per 1000) was the mean of these four age-specific rates. The 20-year risk of dying for a 15-year-old at age 15–34 years is equal to 1–exponential (−20R/1000).We applied this procedure separately to firearm deaths and to all-cause mortality, examining the proportional contribution of firearms to all-cause mortality risk. We defined high-burden and low-burden states in each country as those with the highest and lowest quintiles of firearm death rates, respectively ( appendix pp 3–14 ). We applied the same procedure to estimate firearm and all-cause risk of mortality stratified by sex, age, place of residence, education level, and race or ethnicity. We used Stata (version 15.1) and ArcMap (version 10.5) for statistical analyses.

For each country, we calculated the total number of firearm deaths by year, intent, sex, and age group (0–14 years; 15–34 years; 35–54 years; 55–74 years; ≥75 years) based on the mean of the 5-year age groups, representing linear age standardisation.We calculated age-standardised mortality rates for all-cause deaths and firearm deaths, stratified by sex and subnational-level geographical division (referred to hereafter as state). The USA and Brazil record race or ethnicity and education on death certificates. The education variable has been collected in both countries since 2000, and in Brazil, ethnicity has been collected since 2000. We stratified mortality rates by race or ethnicity in the USA (non-Hispanic black [black], non-Hispanic white [white], and Hispanic subpopulations), and in Brazil (white, black, and brown subpopulations) for the relevant years. We defined education in all countries as either high school or less, or post-secondary.

Our primary analysis compared overall firearm deaths and mortality rates in the four countries at the national and subnational level, stratified by age, sex, education level, and race or ethnicity. Secondary analyses were firearm deaths and mortality rates subclassified by intent: homicide, suicide, unintentional, or undetermined ( appendix p 2 ). Our primary analysis of firearm mortality and comparison with overall all-cause mortality should not be biased by misclassification from death certificate information, in view of the near complete registration data in each country. Firearm deaths are often reported by intent rather than as a common mechanism or exposure risk.Analysis of firearm deaths by both intent and as a single exposure risk enables a more nuanced development of public health responses.

We obtained age-specific, sex-specific, and cause-specific mortality data from 1990–2015 for the USA, Mexico, Brazil, and Colombia from national vital statistics databasesthe US National Center for Health Statistics,Instituto Nacional de Estadística y Geografía,Sistema de Informação sobre Mortalidade,and Departamento Administrativo Nacional de Estadística (DANE).In each country, the underlying cause of death was assigned during routine medical death certification and coded according to the International Classification of Diseases, ninth or tenth revision (ICD-9 or ICD-10). Nearly all deaths in the USA and Mexico are medically certified. In Brazil, medically-certified cause of death coverage was 97% in 2014 (an increase from 87% in the 1990s and 90–95% in the 2000s), and in Colombia mean coverage was 98% in the past decade.Ill-defined causes of death in individuals aged 70 years or younger, which provide a crude assessment of the quality of medical certification, account for less than 2% of all deaths at these ages in the USA, Mexico, and Colombia. In Brazil, ill-defined causes of death accounted for 10% of deaths at these ages between 1990 and 2015, but only around 5% between 2005 and 2015. We obtained population denominators for the USA, Mexico, Brazil, and Colombia from the National Cancer Institute's Surveillance, Epidemiology, and End Results database(which provides more current estimates than the US census), the Mexican Population Council,the Instituto Brasileiro de Geografia e Estatística's Demographic Census data,and DANE,respectively.

Results

Table 1 Characteristics of the study population in the USA, Mexico, Brazil, and Colombia USA Mexico Brazil Colombia Population in 2015 (thousands) 321 538 120 838 201 234 48 203 Male population aged 15–34 years in 2015 (thousands) 44 765 19 946 34 929 8158 Life expectancy at birth in 2015 (years) 80 77 76 75 Total deaths from all causes in 2015 (thousands) 2718 638 1220 219 Total deaths from all causes, 1990–2015 (thousands) 62 583 12 723 26 158 4847 Total firearm deaths, 1990–2015 (thousands) 851 272 855 494 Homicides (%) 342 (40·1%) 225 (82·7%) 766 (89·5%) 463 (93·8%) Suicides (%) 479 (56·3%) 17 (6·2%) 31 (3·6%) 13 (2·7%) Unintentional deaths (%) 22 (2·6%) 17 (6·2%) 11 (1·3%) 2 (0·4%) Undetermined deaths (%) 8 (0·9%) 13 (5·0%) 48 (5·6%) 15 (3·1%) Firearm deaths in men, 1990–2015 (thousands) All ages (%) 730 (2·3%) 252 (3·5%) 799 (5·3%) 459 (16·3%) 0–14 years (%) 10 (1·7%) 4 (0·5%) 11 (0·9%) 5 (2·0%) 15–34 years (%) 332 (22·1%) 144 (16·9%) 579 (28·5%) 305 (53·1%) 35–54 years (%) 210 (5·2%) 82 (6·3%) 173 (5·8%) 125 (27·0%) 55–74 years (%) 121 (1·1%) 19 (0·9%) 32 (0·7%) 21 (2·8%) Firearm deaths in women, 1990–2015 (thousands) All ages (%) 121 (0·4%) 20 (0·4%) 56 (0·5%) 35 (1·8%) 0–14 years (%) 4 (0·8%) 2 (0·2%) 4 (0·4%) 2 (1·0%) 15–34 years (%) 45 (7·8%) 11 (3·6%) 35 (5·9%) 21 (15·7%) 35–54 years (%) 46 (1·9%) 6 (0·9%) 14 (0·9%) 10 (4·1%) 55–74 years (%) 21 (0·3%) 2 (0·1%) 3 (0·1%) 2 (0·3%) 23 UN Department of Economic and Social Affairs Population Division

(2017). World Population Prospects. Data are n or n (%). Numbers are rounded to the nearest thousand. Data obtained from UN World Population Prospects 2017 Revision.The number of sex-specific and age-specific firearm deaths do not sum to total firearm death counts because some values were missing for age-specific counts. Between 1990 and 2015, 106·3 million deaths were recorded in the USA, Mexico, Brazil, and Colombia, of which 2 472 000 were firearm deaths: 851 000 occurred in the USA, 272 000 in Mexico, 855 000 in Brazil, and 494 000 in Colombia ( table 1 ). Of the 2 472 000 firearm deaths, 1 796 000 (72·6%) were homicides, and 540 000 (21·8%) were suicides, with most suicides occurring in the USA ( appendix p 15 ). Homicide accounted for most of the firearm deaths in Colombia (463 000 [93·8%] of 494 000 deaths), Brazil (766 000 [89·5%] of 855 000 deaths), and Mexico (225 000 [82·7%] of 272 000 deaths). Of the 851 000 firearm deaths in the USA, 342 000 (40·1%) deaths were homicides and 479 000 (56·3%) were suicides, with suicide becoming slightly more predominant over time. Table 1 shows the characteristics of the study populations in the four countries.

5 Briceño-Léon R

Villaveces A

Concha-Eastman A Understanding the uneven distribution of the incidence of homicide in Latin America. The overall mortality rates and risk of firearm death differed markedly between states and demographic groups in different countries. Every death per 1000 population corresponds, roughly, to a 2% risk of death in the 15–34 year age group. Among men aged 15–34 years, variability was observed across the four countries with regard to which 5-year age group had the highest firearm mortality rates. In the USA and Brazil, firearm mortality rates were highest among men aged 20–24 years, whereas in Colombia and Mexico, the highest rates of firearm mortality were observed in older age groups ( appendix pp 16–20 ). The 99% CIs were generally narrow, since the numbers of deaths in the major strata were quite large ( appendix p 21 ). Firearm mortality rates were low and generally declined among women, whereas mortality rates in men were higher in all four countries with marked increases and decreases observed between 1990 and 2015 ( appendix p 22 ). In Brazil, the rates of firearm suicide decreased, whereas the rates of firearm homicide increased during the study period. In the USA, the rates of firearm homicide decreased, whereas the rate of suicides increased during the study period. The highest risk of firearm mortality among men aged 15–34 years of any country was observed in Colombia in the 1990s, reaching 4·68% (99% CI 4·67–4·70). However, these high risks declined sharply after 2000, corresponding to a sharp decline in drug-related violence in the country.By 2015, across the four countries, Colombian men aged 15–34 years had the highest risk of firearm mortality (1·88%, 1·87–1·89; appendix pp 16–20) . The coding change from ICD-9 to ICD-10 did not materially alter the observed trends (data not shown).

Figure 1 Subnational geographic variation in the risk of mortality from firearms in the USA, Mexico, Brazil, and Colombia among men aged 15–34 years, 1990-2015 The risk of mortality from firearms varied considerably between states among the 108 million men aged 15–34 years in the four countries ( figure 1 ). In this age group, mortality risk from firearms was highest in the Colombian state of Antioquia (14·15% [99% CI 14·10–14·21]) in the early 1990s. In Mexico, the risk of mortality from firearms markedly increased in high-burden states between 2010 and 2015 (in particular, between 2009 and 2012), driven by large increases in firearm deaths in Chihuahua, Guerrero, Sinaloa, and Durango. In Brazil, the rates of firearm mortality among men increased most in the northeastern region and decreased in the two most populous states of São Paulo and Rio de Janeiro. The high-burden states changed over time in Colombia, Brazil, and Mexico, but remained more stable in the USA ( appendix pp 3–14 ). The subnational variation in firearm mortality was lower in the USA than in Mexico, Colombia, and Brazil, but still remained substantial. In the USA, the District of Columbia had the highest risk of firearm mortality (around 6%) in the 1990s, which was nearly 10 times higher than the comparable national risk, followed by Louisiana and Alaska.

Figure 2 Risk of mortality from firearms among men aged 15–34 years by race, in the USA (A) and Brazil (B), 1990–2015 In the USA, differences in risk of mortality stratified by race or ethnicity were even more pronounced at the state level ( figure 2 ). Among males aged 15–34 years, the risk of firearm mortality was highest in black men, which was four times higher than in white men. The risk of firearm mortality was similar in Hispanic and white men during the study period, but slightly higher among Hispanic men than among white men between 1990 and 2009, and slightly lower between 2010 and 2015 ( figure 2 ).

Figure 3 Risk of mortality from firearm homicide and from all causes among men aged 25–34 years by (A) education, nationally and (B) in selected subpopulations in the USA, Mexico, Brazil, and Colombia, 2000–15 Show full caption 99% CIs and the numerical values are shown in the appendix Analysis stratified by race, intent, and education showed sharper differences among 15–34 year-old men. In the USA, the risk of firearm suicide was higher among young white men than black or Hispanic men, but when focusing on homicide, the pattern changed. The homicide analysis focused on the highest risk age group (men aged 25–34 years). At these ages, black men in the USA with high school or less education had a 1·52% risk (99% CI 1·50–1·54) of mortality from firearm homicide between 2000 and 2015. This risk was 14 times higher than that for comparably educated US white men (0·11% [0·10–0·12]), two to four times higher than for comparably educated Brazilian brown, black, or white men, or Mexican men (range 0·38–0·67%), and 1·5 times higher than comparably educated Colombian men (1·05% [1·03–1·06]; figure 3 ). Among US men with high school or lower education, firearm homicides accounted for three-quarters of the nearly 2% absolute difference in overall mortality risk between black and white men. In the 25–34 year age group, the risk of firearm homicide was five times lower in US black men with post-secondary education than black men with high school or lower education. The risk of firearm homicide was ten times lower in US white men with post-secondary education than white men with high school or lower education. The risk of mortality from firearm homicide was 30 times higher for US black men with university or higher education than comparably educated US white men (0·30% [99% CI 0·28–0·32] vs 0·01% [0·01–0·02]). By contrast, differences in the risk of mortality from firearm homicide in Brazilian men aged 25–34 years were mostly due to differences in education, regardless of race. Between 2000 and 2015, mortality risks from firearm homicides decreased or remained relatively stable in each country and in most subgroups, with the exception of brown men in Mexico and Brazil with high school or lower education, which increased ( figure 3 appendix p 23 ).

Figure 4 Risk of mortality from firearms and from all causes among men at ages 15–34 years in the USA, Mexico, Brazil, and Colombia Show full caption Red boxes indicate the risk of firearm mortality for men aged 15–34 years. White boxes indicate risk of all-cause mortality for men aged 15–34 years. Total death counts (thousands) for firearms and for total deaths from any cause are shown in brackets. Firearm deaths (homicide, suicide, and other) accounted for a large proportion of the all-cause mortality in the 15–34 year age group in all countries ( figure 4 ). In Colombia, firearm deaths accounted for more than half of all deaths from any cause in men aged 15–34 years across the 25-year period. The absolute risk of firearm mortality decreased by 2·8% in Colombia between 1990 and 2015, which accounted for most of the 3·7% absolute decline in all-cause mortality rates ( figure 4 ). In the high-burden states of Colombia, the absolute risk of firearm mortality decreased by 5% between 2000 and 2015, which substantially reduced overall mortality ( appendix p 24 ). In Mexico between 2010 and 2015, firearm deaths accounted for about a quarter of all deaths nationally ( figure 4 ), but an even greater proportion in the high-burden states. In these high-burden states, the variation in firearm deaths seemed to drive changes in all-cause mortality for men aged 15–34 years. In Brazil, the risk of mortality from firearms increased over the 25-year period (from 1·0% to 1·6%) despite an overall decrease in the all-cause mortality risks ( figure 4 ). In the high-burden states of Brazil, firearm deaths accounted for less than a third of all-cause mortality at the start of the study period, but between 2010 and 2015 accounted for almost half. Between 1990 and 2015, firearm mortality and overall mortality declined steadily in the USA ( figure 4 ). In the USA, differences in the risk of firearm mortality between black and white men accounted for most of the overall difference in the risk of mortality among men aged 15–34 years ( appendix p 24 ). About 41%, 17%, and 31% of the absolute decline in all-cause mortality risk among black, white, and Hispanic men aged 15–34 years, respectively, between 1990 and 2015, was attributable to a reduction in firearm mortality rates. In Brazil, firearm deaths made a smaller overall contribution to all-cause mortality rates than in the other three countries.