Table 1: Sociodemographic characteristics of study populations for the main analysis, NT, Qld and NSW (2002–2018).
| Characteristic | NT | Qld | NSW | |||
|---|---|---|---|---|---|---|
| Exposed n (%) | Comparison n (%) | Exposed n (%) | Comparison n (%) | Exposed n (%) | Comparison n (%) | |
| Total sample | A579 | 1,850 | 377 | 2,215 | 97 | 413 |
| Sex | ||||||
| Female | 287 (50) | 920 (50) | 194 (51) | 1,117 (50) | 50 (52) | 203 (49) |
| Male | 292 (50) | 930 (50) | 183 (49) | 1,098 (50) | 47 (48) | 210 (51) |
| AEDC cycle | ||||||
| Cycle 1 (2009,2010) | 110 (19) | 281 (15) | 60 (16) | 372 (17) | 12 (12) | 59 (14) |
| Cycle 2 (2012) | 168 (29) | 543 (29) | 105 (28) | 596 (27) | 16 (16) | 90 (22) |
| Cycle 3 (2015) | 143 (25) | 517 (28) | 95 (25) | 642 (29) | 37 (38) | 136 (33) |
| Cycle 4 (2018) | 158 (27) | 509 (28) | 117 (31) | 605 (27) | 32 (33) | 128 (31) |
| Age at first registration with Medicare1 | ||||||
| 0–0.5 | 545 (95) | 1,692 (91) | 354 (94) | 2,133 (96) | 94 (97) | 394 (95) |
| 0.5–1 | 16 (3) | 60 (3) | 12 (3) | 42 (2) | 0† | 13 (3) |
| 1 and above | 18 (3) | 98 (5) | 11 (3) | 40 (2) | 0† | 6 (1) |
| Age first lived in exposure or comparison area1 | ||||||
| 0–1 | 377 (65) | 1,165 (63) | 243 (64) | 1,389 (63) | 66 (68) | 267 (65) |
| 1–2 | 50 (9) | 203 (11) | 40 (11) | 204 (9) | 12 (12) | 38 (9) |
| 2–3 | 50 (9) | 178 (10) | 33 (9) | 213 (10) | 8 (8) | 33 (8) |
| 3–6 and above | 102 (18) | 304 (16) | 61 (16) | 409 (18) | 11 (11) | 75 (18) |
| Age at AEDC measurement | ||||||
| 4y 7m–5y 0m | 70 (12) | 292 (16) | 47 (12) | 306 (14) | 6 (6) | 24 (6) |
| 5y 1m–5y 6m | 272 (47) | 876 (47) | 187 (50) | 1,034 (47) | 35 (36) | 147 (36) |
| 5y 7m–6y 0m | 204 (35) | 616 (33) | 143 (38) | 822 (37) | 48 (49) | 173 (42) |
| 6y 1m -7y 5m | 33 (6) | 66 (4) | 0† | 53 (2) | 8 (8) | 69 (17) |
| Indigenous status | ||||||
| No | 328 (57) | 1,404 (76) | 283 (75) | 1,968 (89) | 90 (93) | 366 (89) |
| Yes | 251 (43) | 446 (24) | 94 (25) | 247 (11) | 7 (7) | 47 (11) |
| English as second language | ||||||
| No | 423 (73) | 1,520 (82) | 363 (96) | 2,158 (97) | 97 (100) | 404 (98) |
| Yes | 156 (27) | 330 (18) | 14 (4) | 57 (3) | 0† | 9 (2) |
| Remoteness | ||||||
| Very remote | 72 (12) | 209 (11) | ≤5 | 15 (1) | 0 | ≤5 |
| Remote | 268 (46) | 175 (9) | ≤5 | 26 (1) | 12 (12) | ≤5 |
| Outer regional | 97 (17) | 1,027 (56) | 31 (8) | 258 (12) | 10 (10) | 60 (15) |
| Inner regional | 45 (8) | 168 (9) | 292 (77) | 1,524 (69) | 37 (38) | 288 (70) |
| Major cities | 97 (17) | 271 (15) | 45 (12) | 392 (18) | 38 (39) | 61 (15) |
| IRSD2 quintile | ||||||
| 1 (most disadvantaged) | 182 (32) | 354 (19) | 178 (47) | 1,005 (45) | 15 (15) | 88 (21) |
| 2 | 133 (23) | 316 (17) | 110 (29) | 597 (27) | 30 (31) | 111 (27) |
| 3 | 108 (19) | 377 (21) | 34 (9) | 322 (15) | 25 (26) | 96 (23) |
| 4 | 86 (15) | 483 (26) | 48 (13) | 221 (10) | 17 (18) | 87 (21) |
| 5 | 64 (11) | 299 (16) | 7 (2) | 67 (3) | 10 (10) | 31 (8) |
| Missing | 6 | 21 | 0 | 3 | 0 | 0 |
Data sources: Medicare Enrolment File (MEF) (July 2002–December 2017) linked to Australian Early Development Census (AEDC) (2009, 2012, 2015, 2018).
Age at first registration with Medicare and age first lived in an exposure or comparison area were estimated from month and year of birth as recorded on the MEF, with day of birth assumed to be the 15th of the month.
All characteristics except age first lived in an exposure or comparison area were sourced from the AEDC database. Therefore, geographic variables (Australian Bureau of Statistics’ (ABS) Index of Relative Socioeconomic Disadvantage (IRSD) quintile and remoteness) were based on where the child was living at the time of the AEDC, not at the time of living in exposure areas. IRSD decile was based on the Statistical Area Level 1 of the child’s usual residence coded according to ABS Australian Statistical Geography Standard 2016 Version for all cycles. No socioeconomic or remoteness information are collection in the MEF.
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The discrepancies between variables with similar concepts on the MEF and AEDC are as below:
5.0% (278/5,531) records differed in voluntary Aboriginal and Torres Strait Islander identification on the MEF vs. Aboriginal and Torres Strait Islander identification on the AEDC.
0.7% (41/5,531) records differed in sex on the MEF vs. sex on the AEDC.
Denominators for proportions exclude missing values.
Cells have been suppressed or categories collapsed (†) to avoid reporting cell numbers with size ≤5.
Percentages were rounded to integer values.