Maybe his baby will be very intelligent. The baby father ... Alfie Patten with little Maisie

Children fathered by older men are likely to be less intelligent than the offspring of younger dads, Australian and US scientists have found in a report published yesterday.

The surprise result contrasted sharply with earlier studies showing that older mothers produced children more likely to record above average intelligence scores, the researchers concluded.

Lead scientist John McGrath, from the Queensland Brain Institute, said the result was a world first and had implications for men in Western societies who have delayed fatherhood until their 40s or older.

"The results were quite startling as it was thought that the age of the father was less of a concern compared to the age of the mother," McGrath said. "Now we are getting more evidence of the age of the father being just as important - the older a dad is, the worse his children tend to do in intelligence tests."

Researchers examined data collected on 33,000 children in the US between 1959 and 1965 fathered by men aged¹ from 15 to 65. They found that the children of older dads performed less well in intelligence tests conducted at age eight months, four years and seven years.

The researchers said previous studies had linked older fathers to an increased risk of health problems in their children, including schizophrenia, autism, dyslexia, epilepsy and dwarfism.

However, the study published in the journal Public Library of Science Medicine is the first to suggest there is also a link with general intelligence.

The trend towards children of older fathers being less intelligent remained statistically² significant even when factors such as socio-economic status and parental³ mental health were taken into account.

McGrath said the research team could not draw conclusions on how having an older father impacted on children later in life because the subjects in their study were only examined until they were aged seven.

"It is feasible that the offspring of older fathers 'catch up' during later childhood," the researcher said.

"How the subtle neurocognitive features associated with (older fathers) translate into later educational and mental health outcomes across the lifespan remains⁴ to be determined⁵."

美国和澳大利亚的科学家在昨日公布的一份报告中称，年龄较大的男性所生的孩子可能不如年轻男性的孩子聪明。

这一令人惊讶的结果与之前的研究发现形成鲜明对比。之前的研究表明，大龄妈妈所生的孩子智商得分超过平均水平的可能性较大。

昆士兰脑研究所首席科学家约翰•麦克格雷斯称，该研究成果在世界范围内尚属首例，同时对西方国家那些等到40多岁甚至更晚才要孩子的男性具有警示作用。

麦克格雷斯说：“研究结果十分令人吃惊。之前的观点认为，与母亲的年龄相比，父亲的年龄没那么重要。现在有越来越多的证据表明父亲的年龄也很重要，父亲年龄越大，孩子智商测验的得分越低。”

研究人员对1959年至1965年间出生的3.3万名美国儿童的相关数据进行了分析，这些孩子出生时父亲的年龄在15至65岁之间。研究人员发现，从孩子在8个月、4岁和7岁时接受的智商测验结果看，年龄较大的父亲的孩子智商得分较低。

研究人员称，之前的研究表明，父亲年龄偏大会增加孩子患精神分裂症、孤独症、诵读困难、癫痫症和侏儒症等疾病的风险。

而这项发表于《公共科学图书馆：医学》期刊上的研究首次表明，父亲的年龄与孩子的一般智力也有关。

即使将社会经济地位和父母精神健康等因素考虑在内，年龄较大的爸爸易生笨小孩这一趋势从统计角度看也很明显。

麦克格雷斯称，由于该研究在调查对象7岁时就终止了，所以研究小组无法判断父亲年龄偏大会对孩子7岁之后的智力发展造成怎样的影响。

一位研究人员说：“年龄偏大的爸爸所生的孩子的智力在幼年晚期或许会赶上其他孩子，这也是有可能的。”

“目前还不清楚与父亲年龄有关的微妙的神经认知特征对孩子日后的教育和心理健康会造成怎样的影响。”