Incidence per 1000 Persons for ADHD Medication Among Boys Born 2005–2007 by Birth Month
| Age, y . | No. Cases and Incidence (95% CI) January to April . | No. Cases and Incidence (95% CI) May to August . | No. Cases and Incidence (95% CI) September to December . | IRR (95% CI) . | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2005 . | 2006 . | 2007 . | 2005 . | 2006 . | 2007 . | 2005 . | 2006 . | 2007 . | 2005 September to December versus 2006 January to April . | 2006 September to December versus 2007 January to April . | |
| 6 | 45; 4.5 (3.4–6.1) | 69; 6.6 (5.2–8.3) | 68; 6.6 (5.2–8.3) | 101; 9.5 (7.8–11.5) | 74; 6.8 (5.4–8.6) | 111; 10.2 (8.4–12.2) | 116; 10.6 (8.7–12.8) | 112; 11.1 (9.2–13.3) | 131; 13.0 (10.9–15.3) | 1.76 (1.31–2.38)a | 1.69 (1.25–2.29)a |
| 7 | 82; 8.2 (6.7–10.3) | 104; 9.9 (8.1–12.0) | 117; 11.3 (9.4–13.5) | 114; 10.7 (8.9–12.9) | 134; 12.4 (10.5–14.7) | 156; 14.3 (12.2–16.7) | 140; 14.0 (11.8–16.5) | 156; 15.5 (13.2–18.1) | 172; 17.0 (14.7–19.7) | 1.41 (1.09–1.82)a | 1.37 (1.08–1.74)a |
| 8 | 98; 9.9 (8.1–12.0) | 133; 12.7 (10.7–15.0) | 137; 13.2 (11.2–15.6) | 135; 12.7 (10.7–15.0) | 154; 14.2 (12.2–16.7) | 155; 14.2 (12.1–16.6) | 151; 15.1 (12.8–17.6) | 155; 15.4 (13.1–18.0) | 170; 16.8 (14.5–19.5) | 1.19 (0.94–1.50) | 1.16 (0.92–1.46) |
| 9 | 88; 8.9 (7.2–10.9) | 112; 10.7 (8.9–12.8) | 124; 12.0 (10.0–14.3) | 108; 10.2 (8.4–12.2) | 130; 12.0 (10.1–14.3) | 159; 14.6 (12.5–17.0) | 131; 13.1 (11.0–15.5) | 140; 13.9 (11.8–16.4) | 172; 17.0 (14.7–19.7) | 1.22 (0.95–1.58) | 1.16 (0.91–1.48) |
| 10 | 88; 8.9 (7.2–10.9) | 88; 8.4 (6.8–10.3) | 102; 9.9 (8.1–12.0) | 103; 9.7 (8.0–11.7) | 117; 10.8 (9.0–12.9) | 71; 6.5 (5.2–8.2) | 101; 10.1 (8.3–12.2) | 131; 13.0 (10.9–15.4) | 22; 2.2 (1.4–3.3) | 1.20 (0.90–1.60) | 1.31 (1.02–1.71)a |
| 11 | 69; 7.0 (5.5–8.8) | 66; 6.3 (4.9–8.0) | — | 101; 9.5 (7.8–11.5) | 56; 5.2 (4.0–6.7) | — | 77; 7.7 (6.1–9.6) | 10; 1.0 (0.5–1.8) | — | 1.22 (0.88–1.70) | — |
| 12 | 59; 6.0 (4.6–7.7) | — | — | 43; 4.0 (3.0–5.4) | — | — | 17; 1.7 (1.1–2.7) | — | — | — | — |
| Age, y . | No. Cases and Incidence (95% CI) January to April . | No. Cases and Incidence (95% CI) May to August . | No. Cases and Incidence (95% CI) September to December . | IRR (95% CI) . | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2005 . | 2006 . | 2007 . | 2005 . | 2006 . | 2007 . | 2005 . | 2006 . | 2007 . | 2005 September to December versus 2006 January to April . | 2006 September to December versus 2007 January to April . | |
| 6 | 45; 4.5 (3.4–6.1) | 69; 6.6 (5.2–8.3) | 68; 6.6 (5.2–8.3) | 101; 9.5 (7.8–11.5) | 74; 6.8 (5.4–8.6) | 111; 10.2 (8.4–12.2) | 116; 10.6 (8.7–12.8) | 112; 11.1 (9.2–13.3) | 131; 13.0 (10.9–15.3) | 1.76 (1.31–2.38)a | 1.69 (1.25–2.29)a |
| 7 | 82; 8.2 (6.7–10.3) | 104; 9.9 (8.1–12.0) | 117; 11.3 (9.4–13.5) | 114; 10.7 (8.9–12.9) | 134; 12.4 (10.5–14.7) | 156; 14.3 (12.2–16.7) | 140; 14.0 (11.8–16.5) | 156; 15.5 (13.2–18.1) | 172; 17.0 (14.7–19.7) | 1.41 (1.09–1.82)a | 1.37 (1.08–1.74)a |
| 8 | 98; 9.9 (8.1–12.0) | 133; 12.7 (10.7–15.0) | 137; 13.2 (11.2–15.6) | 135; 12.7 (10.7–15.0) | 154; 14.2 (12.2–16.7) | 155; 14.2 (12.1–16.6) | 151; 15.1 (12.8–17.6) | 155; 15.4 (13.1–18.0) | 170; 16.8 (14.5–19.5) | 1.19 (0.94–1.50) | 1.16 (0.92–1.46) |
| 9 | 88; 8.9 (7.2–10.9) | 112; 10.7 (8.9–12.8) | 124; 12.0 (10.0–14.3) | 108; 10.2 (8.4–12.2) | 130; 12.0 (10.1–14.3) | 159; 14.6 (12.5–17.0) | 131; 13.1 (11.0–15.5) | 140; 13.9 (11.8–16.4) | 172; 17.0 (14.7–19.7) | 1.22 (0.95–1.58) | 1.16 (0.91–1.48) |
| 10 | 88; 8.9 (7.2–10.9) | 88; 8.4 (6.8–10.3) | 102; 9.9 (8.1–12.0) | 103; 9.7 (8.0–11.7) | 117; 10.8 (9.0–12.9) | 71; 6.5 (5.2–8.2) | 101; 10.1 (8.3–12.2) | 131; 13.0 (10.9–15.4) | 22; 2.2 (1.4–3.3) | 1.20 (0.90–1.60) | 1.31 (1.02–1.71)a |
| 11 | 69; 7.0 (5.5–8.8) | 66; 6.3 (4.9–8.0) | — | 101; 9.5 (7.8–11.5) | 56; 5.2 (4.0–6.7) | — | 77; 7.7 (6.1–9.6) | 10; 1.0 (0.5–1.8) | — | 1.22 (0.88–1.70) | — |
| 12 | 59; 6.0 (4.6–7.7) | — | — | 43; 4.0 (3.0–5.4) | — | — | 17; 1.7 (1.1–2.7) | — | — | — | — |
IRRs are between boys born in the last third of the year (September to December) and boys born in the first third (January to April) of the following year. CI, confidence interval; —, not applicable.
IRR is significant at P < .05.