Catalano Ralph, Bruckner Tim, Anderson Elizabeth, Gould Jeffrey B
School of Public Health, University of California at Berkeley, Berkeley, CA 94720, USA.
Int J Epidemiol. 2005 Aug;34(4):944-8. doi: 10.1093/ije/dyi081. Epub 2005 Apr 15.
The ratio of male to female live births (i.e. the sex ratio) reportedly falls when populations suffer rare and extreme ambient stressors such as the collapse of national economies. This association has been attributed to the death of male fetuses and to reduced conception of males. We assess the validity of the first of these mechanisms by testing the hypothesis that the fetal death sex ratio varies positively over time with the unemployment rate. Using the unemployment rate also allows us to determine if ambient economic stressors less extreme than collapsing national economies affect the fetal death sex ratio.
We test our hypotheses by applying time-series methods to monthly counts of fetal deaths and the unemployment rate from the state of California beginning January 1989 and ending December 2001. The methods control for trends, seasonal cycles, and other forms of autocorrelation that could induce spurious associations.
Results support the fetal death mechanism in that male fetal deaths increased above the values expected from female deaths and from history in months in which the unemployment rate also increased over its expected value.
Our findings suggest that ambient stressors as common as increasing unemployment elevate the risk of fetal death among males. We discuss the social, economic, and health costs borne by parents and communities afflicted with these fetal deaths.
据报道，当人口遭受罕见且极端的环境压力源（如国家经济崩溃）时，活产男女性别比（即出生性别比）会下降。这种关联被归因于男性胎儿的死亡以及男性受孕率的降低。我们通过检验胎儿死亡性别比随时间与失业率呈正相关这一假设，来评估上述第一种机制的有效性。使用失业率还能让我们确定，比国家经济崩溃程度稍轻的环境经济压力源是否会影响胎儿死亡性别比。
我们通过对1989年1月至2001年12月加利福尼亚州的胎儿死亡月度计数和失业率应用时间序列方法来检验我们的假设。这些方法可控制趋势、季节周期以及其他可能导致虚假关联的自相关形式。
结果支持胎儿死亡机制，即男性胎儿死亡数在失业率也高于预期值的月份中，超过了根据女性死亡数和历史数据预期的数值。
我们的研究结果表明，像失业率上升这样常见的环境压力源会增加男性胎儿死亡的风险。我们讨论了因这些胎儿死亡而给父母和社区带来的社会、经济和健康成本。
