Global burden of BCa
As indicated in Table 1, the prevalence, mortality, and DALYs of BCa were higher in males than in females. It was estimated from GBD 2017 data that there were 2.63 million (95% confidence interval [CI]=2.57–2.72 million) BCa cases, involving 2.03 million (95% CI=1.96–2.11 million) males and 0.60 million (95% CI=0.58–0.62 million) females. There were 200,000 (95% CI=190,000–210,000) deaths from BCa, including 140,000 (95% CI=140,000–150,000) males. BCa resulted in 3.60 million (95% CI=3.48–3.77 million) DALYs, comprising 2.71 million (95% CI=2.60–2.87 million) in males and 0.89 million (95% CI=0.85–0.92 million) in females. The ASP of BCa was 32.91/100,000 persons (95% CI=32.09–33.95/100,000 persons), the ASDR of BCa was 2.57/100,000 persons (95% CI=2.51–2.69/100,000 persons), and the ASR of DALYs of BCa was 45.27/100,000 persons (95% CI=43.73–47.42/100,000 persons). Similarly, the ASP, ASDR, and ASR of DALYs of BCa were higher in males than in females.
Fig. 1 shows the prevalent cases, mortality, and DALYs of BCa according to sex and age group. Within any age group, the value of each of the three indicators was higher in males than in females, with similar trends in males and females. Among both sexes the prevalence was highest in people older than 50 years, increased from 15 to 69 years, decreased slightly from 70 to 79 years, and then increased further in those aged >79 years. According to sex, the prevalence was highest in females aged >79 years and males aged 65–69 years (Fig. 1A). The number of deaths increased with age, and was far larger in those aged >79 years than in the other age groups (Fig. 1B). The trend for DALYs of BCa was similar to that for prevalence, with the difference being that the number of DALYs was largest among those aged >79 years in both males and females (Fig. 1C). Fig. 2 shows the trends of ASP, ASDR, and ASR of DALYs of BCa for the two sexes in the different age groups. All three indicators increased with age in both males and females (Fig. 2).
Burden of BCa at regional and national levels
Among the 21 regions included in GBD 2017, the number of BCa cases was largest in Western Europe (684,364, 95% CI=650,758–718,768) and East Asia (450,488, 95% CI=426143–507850), as were the numbers of deaths due to BCa (43,838, 95% CI=42,016–45,622; and 32,750, 95% CI=31,030–37,532; respectively) and DALYs of BCa (659,027, 95% CI=625,700–693,024; and 621,440, 95% CI=585,238–715,420; respectively). Meanwhile, Oceania had the smallest numbers of cases (1129, 95% CI=1321–944), deaths (102, 95% CI=83–116), and DALYs (2825, 95% CI=2333–3309) (Table 1).
The ASP of BCa was highest in Western Europe (80.17/100,000 persons, 95% CI=76.12–84.12/100,000 persons) and Central Europe (61.55/100,000 persons (95% CI=59.46–63.31/100,000 persons), as were the ASDR (4.21/100,000 persons, 95% CI=4.02–4.38/100,000 persons; and 4.50/100,000 persons, 95% CI=4.34–4.67/100,000 persons, respectively) and the ASR of DALYs (73.07/100,000 persons, 95% CI=69.24–77.13/100,000 persons; and 87.47/100,000 persons, 95% CI=83.82–91.32/100,000 persons; respectively). The ASP of BCa was lowest for South Asia (10.57/100,000 persons, 95% CI=9.86–11.88/100,000 persons) and Andean Latin America (12.38/100,000 persons, 95% CI=11.00–13.95/100,000 persons). The ASDR was lowest for Central Latin America (1.36/100,000 persons, 95% CI=1.30–1.42/100,000 persons) and for Andean Latin America (1.40/100,000 persons, 95% CI=1.26–1.60/100,000 persons), as was the ASR of DALYs (25.04/100,000 persons, 95% CI=23.96–26.21/100,000 persons; and 24.58/100,000 persons, 95% CI=21.90–27.87/100,000 persons; respectively) (Table 1).
Among the 50 most-populous countries globally, the ASP of BCa was highest in Spain (107.48/100,000 persons, 95% CI=97.75–118.63/100,000 persons), followed by Italy, and lowest in Kenya (6.76/100,000 persons, 95% CI=5.49–7.91/100,000 persons), followed by Bangladesh. Egypt showed the highest ASDR of BCa (6.18/100,000 persons, 95% CI=4.71–9.28/100,000 persons) and ASR of DALYs (153.66/100,000 persons, 95% CI=121.00–205.32/100,000 persons), followed by Poland. Kenya had the lowest ASDR of BCa (1.08/100,000 persons, 95% CI=0.86–1.28/100,000 persons), followed by Bangladesh. Bangladesh showed the lowest ASR of DALYs (19.33/100,000 persons, 95% CI=14.48–31.65/100,000 persons) (Supplementary Table 1, Fig. 3).
Relationship between BCa burden and SDI
Among the five GBD SDI quintiles, high-SDI countries showed the highest ASP of BCa (62.51/100,000 persons, 95% CI=60.51–64.54/100,000 persons), ASDR (3.44/100,000 persons, 95% CI=3.34–3.53/100,000 persons), and ASR of DALYs (59.66.81/100,000 persons, 95% CI=57.40–62.14/100,000 persons), followed by countries with high-middle and low-middle SDIs. Low-SDI countries had the lowest ASP (10.16/100,000 persons, 95% CI=9.28–12.00/100,000 persons), while middle-SDI countries had the lowest ASDR (1.69/100,000 persons, 95% CI=1.61–1.88/100,000 persons) and ASR of DALYs (30.81/100,000 persons, 95% CI=29.05–33.88/100,000 persons) (Table 1).
We also analyzed the relationships of ASP, ASDR, and ASR of DALYs of BCa with SDI among the 195 included countries or territories, which revealed positive correlations for all three parameters (P<0.0001, ρ=0.68; P=0.0048, ρ=0.20; and P=0.043, ρ=0.15 for ASR of DALYs; respectively)(Fig.4).
Attributable risk factors of BCa burden
The attributable risk factors for the BCa burden were smoking and high fasting plasma glucose. Globally, 33.72% (95% CI=25.66–41.10%) deaths and 36.80% (95% CI=28.49–43.66%) DALYs caused by BCa could be attributed to smoking. These varied by SDI quintiles, with high-middle-SDI countries showing the highest percentage of smoking-attributable BCa deaths (39.47%, 95% CI=30.58–47.05%) and DALYs of BCa (42.96%, 95% CI=34.26–50.23%), and low-SDI countries showing the lowest percentages (23.22%, 95% CI=14.82–29.95%; and 22.75%, 95% CI=14.01–29.42%, respectively). Globally, 9.87% (95% CI=2.06–21.20%) deaths and 8.91% (95% CI=1.81–19.27%) DALYs caused by BCa could be attributable to high fasting plasma glucose. There were few variations in the percentages of deaths and DALYs caused by high fasting plasma glucose among the five SDI quintiles.