Smoking in male and age of menarche in female influenced BMD.

男性吸烟、女性初潮年龄对骨密度有一定的影响。

youdao

From the above statistics to see that the urban girls as early as the age of menarche in rural girls.

从上面的统计数字要看出，初潮的年龄城市女孩早于农村女孩。

youdao

But in the past 40 years, there hasn't been any real change in age of menarche, which remains at just over 12 years.

但是在过去的40年间，初潮发生的年龄段并没有实质性的改变，还是在12岁左右。

youdao

Epidemiologic studies over the past 40 years have identified numerous risk factors for breast cancer, including: older age, an early age at menarche, a late age at first full-term birth, not having children, a family history of breast cancer in a first-degree relative, greater height, higher circulating estrogen levels, postmenopausal hormone use, breast density, history of breast biopsies, obesity (for postmenopausal breast cancer), and exposure to ionizing radiation.

FORBES: After 40 Years Of Research, What Do We Know About Preventing Breast Cancer?