Table 4. Average and summary ASD PAFs for PTB, SGA, and CD.
Risk factor(s) | 1994 Birth cohort | 2000 Birth cohort | Change in PAF (95% CL*) | ||
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|
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No. of cases | Average PAF, % (95% CL*) | No. of cases | Average PAFs, % (95% CL*) | ||
PTB | 703 | 4.2 (0.0† to 8.7)‡ | 1339 | 2.0 (0.0 to 4.0) | |
SGA | 703 | 0.9 (0.0 to 3.5)‡ | 1339 | 3.1 (1.0 to 5.0) | |
CD | 703 | 7.9 (6.2 to 9.5)‡ | 1339 | 6.7 (3.0 to 10.0) | |
PTB or SGA or CD (summary measure) | 703 | 13.0 (7.7 to 19.5) | 1339 | 11.8 (7.5 to 15.9) | 1.2 (−9.3 to 5.4) |
Subgroup analyses: summary PAFs | |||||
ASD with ID | 234 | 12.3 (1.8 to 23.0) | 377 | 17.1 (8.5 to 25.9) | 4.8 −9.1 to 18.6) |
ASD without ID | 305 | 9.6 (0.8 to 18.6) | 680 | 12.2 (6.2 to 18.5) | 2.6 −8.3 to 13.1) |
ASD, ID Unknown | 164 | 20.5 (9.0 to 31.7) | 282 | 3.4 (0.0 to 12.7) | −17.1 (−31.3 to −2.3) |
Males | 580 | 13.6 (6.9 to 20.2) | 1116 | 10.8 (6.2 to 15.4) | −2.8 (−11.2 to 4.8) |
Females | 123 | 10.2 (0.0 to 24.8) | 223 | 16.3 (6.1 to 26.8) | 6.1 (−12.0 to 24.3) |
Bootstrap CLs based on 1000 replications. A 95% CL was estimated as the 2.5 and 97.5 percentiles of the 1000 replica estimates; each resampled data set comprised case-control sets from the original study sample randomly selected with replacement.
For average PAF estimates, lower bound of CL is reported as 0.0 for all instances in which lower bound estimate was <0.0.
Bootstrap CL could not be directly estimated due to small sample sizes. A hybrid method was used in which information gleaned from the 2000 birth cohort variance estimation was applied to the 1994 cohort data.