CHILDREN who attend day-care centres or playgroups have a 30 per cent less chance of developing a life-threatening cancer, a study has found.

Researchers found that children who had regular contact with their peers and were exposed to a multitude of infections were more likely to develop a stronger immune system, helping them fight the development of the most common form of childhood cancer, acute lymphoblastic leukaemia.

The research, which looked at 14 studies involving more than 20,000 children, is the first of its kind to make a direct link between social contact and leukaemia, which affects about one in 2000 youngsters aged between two and five.

The author of the study and a professor of epidemiology at the University of California, Patricia Buffler, said the analysis bolstered the theory that children exposed to common infections early in life gained protection from the disease.

"It is known that environments such as day-care centres increase the chance of infections spreading," Professor Buffler said.

"Some proponents of the theory believe that if the immune system is not challenged early in life and does not develop normally, it may mount an inappropriate response to infections encountered later in childhood and that this could provoke the development of leukaemia."

Scientists believe that for most types of childhood leukaemia to develop, there first must be a genetic mutation in the foetus, followed by a second trigger during childhood that results in 1 per cent of those children developing the disease. Infection is one of the suspected triggers.

"There is definitely a link between cancer and infection," the chief executive of the NSW Cancer Council, Andrew Penman, said yesterday. "We have seen that recently with cervical cancer, and we know that the age at which infection occurs can determine the outcome, but this research raises a lot of questions without answering any of them."

The president of Childcare Associations Australia, Amanda Morphett, said the findings indicated that "well regulated, quality assured care has a positive impact on children's growth and development".

"If there is an upper respiratory, viral or gastro type of infection to be caught, children who are new to care tend to be the first to catch it, [but] anecdotal evidence suggests that those who have participated in high social contact situations are better able to manage exposure to both viral and bacterial infection," she said.

But parents should not to rush to send their child to a day-care centre on the basis on the study, warned David Ziegler, a pediatric oncologist at the Sydney Children's Hospital.

"We're happy to look closely at anything which can help us work out what causes leukaemia, but we are talking about something that is already very, very rare, so the change for a child going to child care would be tiny. I'd urge parents to be cautious."

研究發現，參加日托或者進幼兒園的兒童可能減少 30 ％ 發生威脅生命的癌癥的機會。

研究人員發現，經常與他們的小朋友接觸的以及暴露于感染群體的兒童更有可能獲得一個強大的免疫系統，幫助他們抗擊最常見的兒童癌癥形式——急性淋巴細胞白血病的發展。

這項調查，查看了 14 項涉及 20,000 以上兒童的研究，是第一次這類在社會接觸和白血病之間建立直接聯系的調查。白血病，大約影響兩歲到五歲之間幼童的 2,000 分之一。

該研究報告的作者，加州大學的流行病學教授帕特里夏 比夫萊說，結果分析支持了這樣的理論，即兒童在生活的早期暴露于常見的感染能夠增進對疾病防護。

教授比夫萊說：“這是眾所周知的，例如日托中心那樣的環境，會增加感染蔓延的機會。”

“一些支持這種理論的人認為，如果免疫系統沒有在生活早期遇到挑戰并且未能正常發展，它可能對幼童后來遇到的感染掛載一個不恰當的回應，而這可能挑起白血病的發展。” 

科學家們認為，大多數類型兒童白血病的發生，首先必定是在胎兒期的基因變異，然后是在童年期的第二次觸發，結果是這些兒童的 1％ 發生疾病。感染是懷疑的誘因之一。

“在癌癥和感染之間肯定有聯系，”新南威爾士州癌癥理事會的行政主管安德魯 彭曼昨天表示。“我們最近對于子宮頸癌已經看到，而且我們知道感染發生的年齡可能決定未來的結果，但是這項研究提出了很多沒能回答的問題。”

澳大利亞托兒協會的主席阿曼達 莫費特說，調查結果顯示，“良好的管理、有質量保證的照料對兒童的成長與發展產生了積極的影響。” 

“如果趕上上呼吸道，病毒或腸道類型的感染，那些新照看的孩子趨向于首先被感染，[但是]傳聞證據表明，那些參與高社會接觸情況的孩子能夠較好地抗御對于病毒和細菌兩者感染的暴露，”她說。

但是，父母們不應該基于這項研究急于將他們的孩子送往日托中心，悉尼兒童醫院的兒科腫瘤學家戴維 齊格勒警告說。

“我們很高興能夠仔細研究可以幫助我們找出白血病病因的任何事情，但是我們所談論的事情已經是非常、非常罕見的了，所以孩子去往幼托的改變可能是極微小的。我呼吁家長們要慎重。”