The overall combined estimate for the past year recall period was 0.30% (CI: 0.19%–0.41%) (Table 3). Q statistics and I2 indicate heterogeneity of results across these surveys (Q2 = 11.7, P <.01, I2 = 82.9). The combined past-year estimate for males was 0.36% (CI: 0.26%–0.47%) and for females was 0.21% (CI: 0.10%–0.32%). Applying these proportions to the U.S. population age 13 years or older for 2011, we estimate that approximately 774,434 adults and adolescents (range: 494,605–1,054,263) injected drugs in the past year in the United States.
