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Table 1 Bias due to ignoring the exposure duration to the host country and type of migration expressed as the mean hazard ratio (HR) and standard deviation (SD) for risk of CVD between a cohort with continuous migration (Cohort 2, reference) and a cohort with a one-wave migration for various hazard of return migration (Cohort 1). Mean sample sizes (ss) for each cohort are given for varying return migration (R-M) hazards

From: Bias in cohort-based comparisons of immigrants’ health outcomes between countries: a simulation study

No risk of CVD due to exposure 5-year exposure increases risk of CVD by 2.5%
Mean values
 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80
 SS Cohort 1 1491 3729 7459 1454 3634 7269 1403 3509 7017 SS Cohort 1 1436 3589 7178 1407 3516 7035 1369 3421 6845
 SS Cohort 2 (ref) 1713 4283 8567 1692 4229 8458 1663 4157 8313 SS Cohort 2 (ref) 1686 4215 8429 1669 4171 8343 1646 4113 8226
 CVD cases 56 141 283 57 141 282 57 141 282 CVD cases 83 207 413 83 207 413 83 207 413
HR 1.00 0.98 0.96 1.01 0.97 0.97 1.02 0.98 0.98 HR 1.11 1.08 1.07 1.11 1.09 1.08 1.11 1.09 1.08
(SD) (0.30) (0.17) (0.12) (0.31) (0.18) (0.12) (0.31) (0.18) (0.12) (SD) (0.27) (0.17) (0.12) (0.28) (0.16) (0.11) (0.27) (0.17) (0.11)
5-year exposure increases risk of CVD by 0.1% 5-year exposure increases risk of CVD by 5%
Mean values
 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80
 SS Cohort 1 1490 3724 7450 1452 3631 7261 1402 3506 7011 SS Cohort 1 1357 3390 6782 1338 3345 6689 1314 3284 6568
 SS Cohort 2 (ref) 1713 4281 8563 1691 4227 8455 1662 4155 8309 SS Cohort 2 (ref) 1648 4119 8240 1635 4089 8178 1618 4046 8092
 CVD cases 57 143 287 57 143 287 57 144 287 CVD cases 118 294 589 118 294 588 118 294 588
HR 1.01 0.98 0.97 1.01 0.98 0.97 1.02 0.99 0.98 HR 1.21 1.19 1.19 1.21 1.20 1.19 1.21 1.20 1.19
(SD) (030) (017) (012) (030) (017) (012) (030) (018) (012) (SD) (024) (015) (011) (024) (015) (010) (025) (015) (011)
5-year exposure increases risk of CVD by 0.5% 5-year exposure increases risk of CDV by 10%
Mean values
 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80
 SS Cohort 1 1482 3705 7411 1445 3615 7230 1398 3495 6989 SS Cohort 1 1117 27937 55867 1114 2784 5567 1109 2772 5544
 SS Cohort 2 (ref) 1709 4271 8543 1688 4219 8440 1660 4149 8298 SS Cohort 2 (ref) 1536 3840 7681 1532 3829 7657 1525 3812 7624
 CVD cases 61 153 305 61 153 306 61 153 306 CVD cases 203 507 1015 203 508 1015 203 507 1015
HR 1.03 0.99 0.98 1.03 1.00 0.99 1.03 1.01 1.00 HR 1.48 1.47 1.47 1.48 1.47 1.47 1.48 1.47 1.46
(SD) (0.31) (0.17) (0.12) (0.30) (0.17) (0.12) (0.29) (0.17) (0.12) (SD) (0.23) (0.14) (0.10) (0.23) (0.14) (0.10) (0.23) (0.14) (0.10)
5-year exposure increases risk of CVD by 1% 5-year exposure increases risk of CDV by 20%
Mean values Mean values
 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80 R-M hazard 1.20 1.20 1.20 1.00 1.00 1.00 0.80 0.80 0.80
 SS Cohort 1 1472 3679 7358 1438 3592 7187 1392 3479 6958 SS Cohort 1 1482 1206 2411 482 1205 2412 482 1206 2412
 SS Cohort 2 (ref) 1703 4259 8517 1683 4209 8418 1656 4142 8283 SS Cohort 2 (ref) 1225 3064 6129 1225 3061 6124 1223 3057 6115
 CVD cases 66 165 330 66 165 330 66 165 330 CVD cases 254 636 1272 255 635 1272 254 636 1272
HR 1.04 1.02 1.01 1.05 1.02 1.01 1.05 1.02 1.02 HR 2.91 2.89 2.88 2.90 2.88 2.87 2.90 2.88 2.87
SD) (0.28) (0.17) (0.12) (0.29) (0.17) (0.12) (0.29) (0.17) (0.12) (SD) (0.38) (0.24) (0.17) (0.38) (0.24) (0.16) (0.37) (0.23) (0.17)