Background
Methods
Study design and recruitment
Data collection
Variables
Statistical analyses
Results
Age at menarche | ||||
---|---|---|---|---|
Total (%) N = 1,275,000 | Mean (SD) | 95% CI | P value | |
Birth cohorta | <0.0001 | |||
<1970s | 3380(0.261) | 14.119(1.405) | 14.072–14.166 | |
1970s | 109,206(8.446) | 13.866(1.283) | 13.859–13.874 | |
1980s | 575,938(44.542) | 13.755(1.233) | 13.752–13.759 | |
1990s | 575,103(44.477) | 13.613(1.170) | 13.610–13.616 | |
Early 2000s | 4985(0.386) | 13.296(1.039) | 13.267–13.325 | |
Ethnic groupb | <0.0001 | |||
Han | 814,111(63.852) | 13.671(1.179) | 13.669–13.674 | |
Yi | 152,381(11.951) | 13.772(1.281) | 13.765–13.778 | |
Dai | 46,448(3.643) | 13.610(1.237) | 13.599–13.621 | |
Bai | 38,134(2.990) | 13.842(1.329) | 13.829–13.856 | |
Miao | 38,420(3.013) | 13.655(1.141) | 13.644–13.666 | |
Hani | 37,022(2.904) | 13.792(1.291) | 13.779–13.805 | |
Zhuang | 32,857(2.577) | 13.665(1.235) | 13.652–13.679 | |
Lisu | 24,760(1.942) | 14.058(1.369) | 14.041–14.075 | |
Hui | 15,487(1.215) | 13.403(1.099) | 13.386–13.420 | |
Laku | 13,802(1.183) | 13.721(1.220) | 13.701–13.741 | |
Wa | 12,679(0.994) | 13.631(1.103) | 13.611–13.650 | |
The othersc | 41,106(3.224) | 13.865(1.307) | 13.853–13.878 | |
Area of residenced | <0.0001 | |||
Rural | 1,231,899(96.620) | 13.707(1.212) | 13.705–13.709 | |
urban | 43,094(3.380) | 13.477(1.181) | 13.466–13.488 | |
Economic status | <0.0001 | |||
Extreme poverty | 343,014(26.903) | 13.799(1.142) | 13.795–13.803 | |
Middling poverty | 549,681(43.112) | 13.711(1.235) | 13.708–13.714 | |
Non-poverty | 382,305(29.985) | 13.593(1.231) | 13.589–13.597 |
Age at menarche in ethnic groups
Age at Menarche – years±SD (95%CI)a | P for trend | ||||||
---|---|---|---|---|---|---|---|
<1970s | 1970s | 1980s | 1990s | Early 2000s | Difference | ||
Ethnic group | |||||||
Han | 14.085 ± 1.361 (14.029–14.142) | 13.820 ± 1.240 (13.811–13.828) | 13.715 ± 1.19 4(13.711–13.719) | 13.595 ± 1.144 (13.592–13.599) | 13.298 ± 1.039 (13.256–13.340) | (− 0.7876)(− 0.8574,-0.7178) | <0.0001 |
Yi | 14.180 ± 1.498 (14.008–14.352) | 13.939 ± 1.368 (13.914–13.964) | 13.834 ± 1.303 (13.824–13.843) | 13.678 ± 1.234 (13.669–13.688) | 13.408 ± 1.159 (13.305–13.511) | (− 0.7725)(− 0.9604,-0.5846) | <0.0001 |
Dai | 14.019 ± 1.352 (13.646–14.391) | 13.813 ± 1.302 (13.763–13.864) | 13.655 ± 1.250 (13.639–13.672) | 13.544 ± 1.211 (13.527–13.560) | 12.979 ± 1.143 (12.791–13.168) | (− 1.0397)(− 1.4207,-0.6587) | <0.0001 |
Bai | 14.413 ± 1.696 (14.166–14.660) | 14.029 ± 1.366 (13.986–14.071) | 13.898 ± 1.342 (13.879–13.917) | 13.711 ± 1.280 (13.690–13.732) | 13.053 ± 1.038 (12.711–13.394) | (− 1.3604)(− 1.9239,-0.7969) | <0.0001 |
Miao | 14.202 ± 1.471 (13.901–14.503) | 13.962 ± 1.275 (13.909–14.016) | 13.802 ± 1.182 (13.782–13.822) | 13.552 ± 1.091 (13.538–13.567) | 13.280 ± 0.946 (13.222–13.339) | (− 0.9218)(− 1.1336,-0.71) | <0.0001 |
Hani | 14.329 ± 1.527 (14.079–14.579) | 14.152 ± 1.456 (14.103–14.201) | 13.950 ± 1.353 (13.929–13.970) | 13.563 ± 1.14 1(13.545–13.580) | 13.255 ± 1.087 (13.049–13.460) | (− 1.0742)(− 1.4114,-0.737) | <0.0001 |
Zhuang | 14.000 ± 1.449 (13.680–14.320) | 13.868 ± 1.358 (13.816–13.920) | 13.732 ± 1.263才 (13.711–13.754) | 13.576 ± 1.181 (13.558–13.594) | 13.211 ± 1.013 (13.069–13.353) | (− 0.7889)(− 1.0887,-0.4892) | <0.0001 |
Lisu | 14.119 ± 1.274 (13.809–14.430) | 14.224 ± 1.521 (14.153–14.296) | 14.158 ± 1.409 (14.130–14.186) | 13.971 ± 1.313 (13.948–13.993) | 13.532 ± 0.958 (13.395–13.669) | (− 0.5878)(− 0.8812,-0.2944) | 0.0001 |
Hui | 13.885 ± 1.451 (13.298–14.471) | 13.583 ± 1.169 (13.506–13.661) | 13.456 ± 1.117 (13.427–13.486) | 13.353 ± 1.080 (13.331–13.376) | 13.000 ± 0.977 (12.706–13.294) | (− 0.8846)(− 1.4602,-0.309) | 0.0031 |
Laku | 14.000 ± 1.291(13.570–14.430) | 13.968 ± 1.280 (13.887–14.050) | 13.824 ± 1.237 (13.792–13.857) | 13.616 ± 1.186 (13.588–13.644) | 13.179 ± 1.111 (12.976–13.383) | (−0.8205)(−1.2514,-0.3896) | 0.0002 |
Wa | 13.692 ± 1.104c (13.334–14.050) | 13.720 ± 1.041 (13.658–13.783) | 13.651 ± 1.090 (13.623–13.679) | 13.595 ± 1.127 (13.565–13.624) | 12.979 ± 1.053 (12.670–13.288) | (−0.7136)(−1.1771,-0.25) | 0.003 |
The othersb | 14.213 ± 1.473 (13.874–14.552) | 14.085 ± 1.394c (14.036–14.135) | 13.929 ± 1.333 (13.910–13.949) | 13.770 ± 1.257 (13.752–13.789) | 13.389 ± 1.024c (13.252–13.526) | (−0.8244)(−1.1293,-0.5196) | <0.0001 |
Area of residence | |||||||
Rural | 14.141 ± 1.404 (14.092–14.191) | 13.884 ± 1.286 (13.876–13.892) | 13.767 ± 1.234 (13.763–13.770) | 13.619 ± 1.169 (13.616–13.622) | 13.296 ± 1.038c (13.267–13.325) | (−0.845)(− 0.8984,-0.7917) | <0.0001 |
urban | 13.841 ± 1.391 (13.669–14.014) | 13.621 ± 1.215 (13.594–13.649) | 13.488 ± 1.175 (13.473–13.503) | 13.361 ± 1.154 (13.341–13.382) | 13.154 ± 1.14 4(12.463–13.845) | (−0.6874)(−1.4606,0.0858) | 0.0812 |
Economic status | |||||||
Extreme poverty | 14.155 ± 1.327c (14.072–14.238) | 14.008 ± 1.259 (13.993–14.023) | 13.870 ± 1.163 (13.864–13.876) | 13.712 ± 1.196 (13.706–13.717) | 13.391 ± 1.034 (13.346–13.435) | (−0.7645)(− 0.8507,-0.6783) | <0.0001 |
Middling poverty | 14.178 ± 1.456 (14.103–14.252) | 13.906 ± 1.316c (13.894–13.918) | 13.784 ± 1.252 (13.779–13.789) | 13.605 ± 1.190 (13.600–13.610) | 13.215 ± 1.023 (13.174–13.256) | (−0.9627)(−1.0416,-0.8837) | <0.0001 |
Non-poverty | 13.990 ± 1.398 (13.901–14.080) | 13.711 ± 1.240 (13.698–13.724) | 13.631 ± 1.247 (13.626–13.637) | 13.519 ± 1.205c (13.513–13.525) | 13.285 ± 1.092c (13.195–13.376) | (−0.7052)(− 0.8405,-0.57) | <0.0001 |