室内生活型态与儿童近视有关


  【24drs.com】根据荷兰的一篇研究,即使是在孩童学会阅读之前,户外活动时间太少,对他们的近视风险就有负面影响;另外,根据在中国进行的一篇研究,室内生活型态的孩童,每天有户外活动时,近视风险显著降低。
  
  荷兰鹿特丹Erasmus医学中心博士候选人、Utrecht应用科技大学视力矫正与验光科、前述荷兰研究的第一作者Jan Roelof Polling表示,即使是年轻的视力正常儿童,花在户外的时间和近距离作业的时间都与视轴长度有关。
  
  他们发现,每天在户外时间少于45分钟的孩童,每天近距离作业以及使用计算机超过2小时的孩童,视轴最长。
  
  Polling在视力与眼科研究协会2014年会中发表「Generation R」研究的结果。
  
  对6,690名各种族孩童,在6岁时进行视力与视轴长度检查。这些孩童的整体近视盛行率是1.9%,荷兰孩童是0.9%,非西方移民孩童达3.2%,视轴长度中位数是22.35 mm (范围19.27-25.05 mm)。
  
  其中4,059名孩童有完成关于户外活动时间的问卷,相较于每天户外活动时间大于2小时的孩童,每天户外活动时间小于1小时孩童的视轴长度显著较长(22.41 vs 22.33 mm;P< .001)。
  
  此外,相较于每天户外活动时间大于2小时的孩童,每天户外活动时间小于1小时孩童之视轴长度大于平均值的风险达34%以上(胜算比1.34;95%信心区间1.14- 1.58)。
  
  视轴长度和长时间近距离作业之间的关联并不显著(P= .14),不过,Polling报告指出,探讨曝露值四分位数与近距离作业的多变项分析发现,有显著趋势。
  
  他解释,两种因素对于眼睛发育各有影响。近视风险增加之孩童(例如家人有近视者),即便他们还很小,应鼓励他们每周至少有15小时在户外,避免长时间近距离作业。
  
  在这场研讨会中,另一篇3年纵向研究也提到近视和花在户外时间的关联,这篇在中国广州进行的研究包括了12所小学、超过2,000名的一年级孩童。
  
  东亚的近视率特别高;研究者将这归因于孩童的家庭作业要求严格所致,让他们得待在室内专注于需近距离完成的作业。
  
  这些学童被随机分组,每天45分钟户外活动或维持一般作息;在开始时,户外组和对照组的近视和等效球镜度数盛行率相当。3年后,户外组的近视盛行率显著低于对照组(30.4% vs 39.5%; P < .001)。
  
  研究者结论指出,这些结果证明,透过学校增加学童的户外活动时间量,可减少发生近视的孩童人数。
  
  澳洲坎培拉澳洲国立大学生物研究院、第一作者Ian Morgan博士解释,这篇研究附属于一项减少近视的公众教育活动。
  
  Morgan博士解释,增加户外活动时间的公卫介入效果不错,但是在东亚,必须相当程度地减少家庭作业量才可能,家庭作业多是学童没有足够户外活动时间的主要因素。
  
  目前还不清楚户外活动和近视之关联的机转,但是Morgan博士提出两个主要怀疑 —多巴胺和曝露于紫外光(UV),他表示,动物研究的证据有利于光线/多巴胺假设,但是需要临床试验来解决这个议题。
  
  不过,他解释,流行病学研究难以区分释放多巴胺和增加UV曝露的影响程度,因为在户外时,会曝露于更多光线、更多UV,也会释放更多多巴胺。
  
  会议主持人、俄亥俄州立大学眼科学院Donald Mutti博士表示,这篇研究提供了孩童近视盛行率的证据;这篇研究不错,对近视盛行率高的这些人,以纵向研究方式再度证明户外活动对于发生近视有保护效果。
  
  Mutti博士表示,这篇研究和我们以前的研究结果一致(Invest Ophthalmol Vis Sci. 2012;53:7169-7175),花在户外的时间对发生近视有某程度的保护效果,但是孩童一旦发生近视,则对其病程影响不大。
  
  他指出,Polling等人的研究贡献在于,证明户外活动对视力正常孩童的影响。
  
  这篇研究证明户外活动时间对于幼童的视轴长度有影响。
  
  Mutti博士表示,近视和更严重的眼科疾病风险增加有关,包括青光眼,白内障和视网膜剥离,而近视本身对公卫也有重大影响。
  
  他表示,即使眼睛健康,消费者和保险公司每年在诊断和处理屈光度的财务负担达数十亿美元,在美国和全世界,未矫正的屈光度是可矫正之视力障碍的主因。
  
  资料来源:http://www.24drs.com/professional/list/content.asp?x_idno=7079&x_classno=0&x_chkdelpoint=Y
  

Indoor Lifestyle Linked to Myopia in Children

By Nancy A. Melville
Medscape Medical News

ORLANDO, Florida — Spending too little time outdoors has a negative effect on the risk for myopia in children, even before they learn to read, according to a study conducted in the Netherlands.

However, when children with indoor lifestyles are subjected to daily outdoor exposure, rates of myopia significantly decrease, according to a study conducted in China.

Even in young emmetropic children, the amount of time spent outdoors and on near work is associated with axial length, said Jan Roelof Polling, from the division of orthoptics and optometry at the University of Applied Sciences Utrecht, and PhD candidate at Erasmus Medical Center in Rotterdam, the Netherlands. He was lead investigator on the Dutch study.

"We found that children who played outside less than 45 minutes a day and those spending more than 2 hours a day on near work and computer games had the longest eyes," he told Medscape Medical News.

Polling presented results from the Generation R study here at Association for Research in Vision and Ophthalmology 2014 Annual Meeting.

A population of 6690 multiethnic children were examined for visual acuity and axial length at 6 years of age.

The prevalence of myopia in the cohort was 1.9%, which ranged from 0.9% in Dutch children to 3.2% in non-Western immigrants. Median axial length was 22.35 mm (range, 19.27 to 25.05 mm).

Completed questionnaires provided information on time spent outdoors for 4059 children. Axial length was significantly longer in children who spent less than 1 hour per day outdoors than in those who spent more than 2 hours outdoors (22.41 vs 22.33 mm; P < .001).

In addition, children who played outside for less than 1 hour per day had a 34% greater risk of having an axial length above average than children who spent more than 2 hours outdoors (odds ratio, 1.34; 95% confidence interval, 1.14 - 1.58).

The association between axial length and the amount of time spent doing near work was not significant (P = .14). However, a multivariate analysis looking at quartiles of exposure and near work showed significant trends, Polling reported.

"Both factors had an independent effect on eye growth. Children with an increased risk of near-sightedness, such as those from a near-sighted family, should be prompted to spend at least 15 hours a week outside and should avoid spending long hours doing near work, even when they are very young," he explained.

The association between myopia and time spent outdoors was also seen in a 3-year longitudinal study, which was presented during the same session. It involved more than 2000 first-grade children at 12 primary schools in Guangzhou, China.

Rates of myopia are exceptionally high in East Asia; researchers attribute this to the intensely rigorous homework requirements placed on children, keeping them indoors and focused on near-work activities.

The students were randomly assigned to 45 minutes of outdoor activity daily or to usual behavior. At baseline, the prevalence of myopia and mean spherical equivalence were similar in the outdoor and control groups.

After 3 years, the incidence of myopia was significantly lower in the outdoor group than in the control group (30.4% vs 39.5%; P < .001).

"These results provide proof of principle that increasing the amount of time that children spend outdoors through the school system can decrease the number of children who become myopic," the researchers conclude.

The study was conducted as part of a public education campaign designed to reduce myopia, explained lead investigator Ian Morgan, PhD, from the Research School of Biology at the Australian National University in Canberra.

The public health intervention to increase time spent outdoors worked well, but in East Asia, "it will almost certainly need to be backed up by a reduction in homework demands, which is a major factor in students not having enough time outdoors," Dr. Morgan explained.

The mechanisms behind the relation between outdoor exposure and myopia are not clear, but Dr. Morgan offered 2 prime suspects — dopamine and exposure to ultraviolet (UV) light. "Evidence from animal studies favors the light/dopamine hypothesis, but we need a clinical trial to resolve the issue," he said.

However, "it will be hard to distinguish in epidemiologic studies between dopamine release and increased UV exposure, because when you go outside, you get more light, more UV, but you also get more dopamine release," he explained.

This study provides support for evidence on myopia in children, said session moderator Donald Mutti, OD, PhD, from the College of Optometry at Ohio State University in Columbus.

"The study is a nice, longitudinal replication showing a protective effect against the onset of myopia in a population that has a very high prevalence of myopia," he told Medscape Medical News.

"It is also very nice replication of our group's finding that time outdoors seems to have some protective effect against the onset of myopia, but has little effect on the rate of progression once a child becomes myopic," said Dr. Mutti (Invest Ophthalmol Vis Sci. 2012;53:7169-7175).

He added that the study by Polling's team contributes to his group's findings by showing effects on emmetropic children.

"That study extends the field by showing that time outdoors has an effect on length in young children," he said.

Myopia is associated with an increased risk for more serious eye diseases, including glaucoma, cataracts, and retinal detachment, but even on its own, the condition has important public health implications, Dr. Mutti said.

"Even if the eye remains healthy, there is a financial burden reaching billions of dollars each year on consumers and insurers to diagnose and manage refractive error," he said. "Uncorrected refractive error is a major source of correctable visual impairment in the United States and around the world. "

Mr. Polling and Dr. Morgan have disclosed no relevant financial relationships. Dr. Mutti reports being a consultant for Vistakon Johnson & Johnson on issues related to myopia.

Association for Research in Vision and Ophthalmology (ARVO) 2014 Annual Meeting: Abstracts 1271 and 1272. Presented May 5, 2014.

    
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