Despite the large literature examining socioeconomic predictors of fertility and the influence of reproductive history on post-reproductive mortality, previous research has not offered a population-level perspective on how male health in early adulthood is related to subsequent fertility. Using Swedish population registers and military conscription data, we study how body mass index (BMI), physical fitness and height are associated with total fertility and parity transitions by 2012 amongst 405,427 Swedish men born 1965-1972, meaning we observe fertility up to age 40 or older. Applying linear regression as well as sibling fixed effects, we find that our anthropometric measures are strong predictors of later fertility, even after accounting for educational attainment and cumulative income up to age 40. Men with a 'normal' BMI and in the highest decile of physical fitness have the most children by the end of our follow-up period. Men who were already obese at ages 17-20 had a relative probability of childlessness almost twice as high as men who had a 'normal' BMI at ages 17-20, and men in the bottom decile of physical fitness had a relatively probability of childlessness almost 50% higher than men in the top decile of physical fitness. These patterns were at least as strong in our models applying the sibling fixed effects design. We find that the association between male height and fertility is curvilinear in models estimated without sibling fixed effects, but only men in the lowest decile of height have lower fertility in sibling comparison models. Further analyses show that the strong associations between our anthropometric measures and male fertility persist even amongst men who married. We discuss the implications of our findings for fertility in high-income countries in light of secular increases in the prevalence of overweight/obesity.

中文翻译：

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成年早期健康对男性生育能力的影响

尽管大量文献研究了生育率的社会经济预测因素以及生育史对生育后死亡率的影响，但之前的研究并未提供关于成年早期男性健康与随后生育率之间的关系的人口层面观点。使用瑞典人口登记和军队征兵数据，我们研究了 2012 年 405,427 名出生于 1965-1972 年的瑞典男性的体重指数 (BMI)、身体素质和身高与总生育率和胎次变化之间的关系，这意味着我们观察到 40 岁之前的生育率或更老。应用线性回归以及兄弟固定效应，我们发现我们的人体测量指标是以后生育率的有力预测指标，即使考虑到教育程度和 40 岁之前的累计收入。 男性“正常” 到我们的随访期结束时，BMI 和身体素质最高十分位数的孩子最多。17-20 岁已经肥胖的男性无子女的相对概率几乎是 17-20 岁体重“正常”男性的两倍，而身体素质处于最低十分位数的男性无子女的概率相对较高在身体健康的前十分之一中，几乎比男性高出 50%。这些模式在我们应用兄弟固定效应设计的模型中至少同样强大。我们发现，在没有兄弟姐妹固定效应的估计模型中，男性身高和生育率之间的关联是曲线的，但在兄弟姐妹比较模型中，只有身高最低十分位数的男性生育率较低。进一步的分析表明，即使在已婚男性中，我们的人体测量指标与男性生育能力之间的强关联仍然存在。鉴于超重/肥胖患病率的长期增长，我们讨论了我们的研究结果对高收入国家生育率的影响。