Older men are more likely than young ones to father a child who develops autism or schizophrenia, because of random mutations that become more numerous with advancing paternal age, scientists reported on Wednesday, in the first study to quantify the effect as it builds each year. The age of mothers had no bearing on the risk for these disorders, the study found.

　　专家说，年长的男性大可不必因为这项研究的结果而放弃当父亲，但这也许会影响他们关于生育下一代的决定。 男人在40多岁或更年长时要孩子的话，总体风险最高是2%，此外还有一些完全未知的生理因素也会产生影响。

　　Experts said that the finding was hardly reason to forgo fatherhood later in life, though it may have some influence on reproductive decisions. The overall risk to a man in his 40s or older is in the range of 2 percent, at most, and there are other contributing biological factors that are entirely unknown.

　　但是，这项在《自然》(Nature)杂志网站发表的研究支持了这样一种观点，即自闭症的确诊率在近几十年来快速上升，部分是由于男性作父亲的平均年龄的提高，有20-30%的病例与此有关。

　　But the study, published online in the journal Nature, provides support for the argument that the surging rate of autism diagnoses over recent decades is attributable in part to the increasing average age of fathers, which could account for as many as 20 to 30 percent of cases.

　　这次研究的发现也反驳了长期存在的一种观点，即认为母亲的年龄是决定孩子出现发育问题几率的最重要因素。大龄母亲会增加染色体异常的风险，如唐氏综合征。但是，当涉及一些复杂的发育和精神问题时，研究发现大部份的遗传风险源于精子，而不是卵子。

　　The findings also counter the longstanding assumption that the age of the mother is the most important factor in determining the odds of a child having developmental problems. The risk of chromosomal abnormalities, like Down syndrome, increases for older mothers, but when it comes to some complex developmental and psychiatric problems, the lion’s share of the genetic risk originates in the sperm, not the egg, the study found.

　　此前的一些研究，包括一篇在4月发表的分析报告，也显示了同样的结论，这种风险在35岁时大于25岁，且会随着年龄的增加而同步攀升。这次的新报告则首次将风险量化，计算了风险每年会增加多少。

　　Previous studies had strongly suggested as much, including an analysis published in April that found that this risk was higher at age 35 than 25 and crept up with age. The new report quantifies that risk for the first time, calculating how much it accumulates each year.

　　研究小组发现，一个20岁父亲所生的孩子会携带25个可以追溯到父亲遗传物质的基因突变 。突变的数量每年稳定增加两个，在父亲40岁的新生儿中达到65个。

　　The research team found that the average child born to a 20-year-old father had 25 random mutations that could be traced to paternal genetic material. The number increased steadily by two mutations a year, reaching 65 mutations for offspring of 40-year-old men.

　　研究还发现，来自母亲的平均突变数是15个，无关她的年龄。

　　The average number of mutations coming from the mother’s side was 15, no matter her age, the study found.