室內生活型態與兒童近視有關


  【24drs.com】根據荷蘭的一篇研究,即使是在孩童學會閱讀之前,戶外活動時間太少,對他們的近視風險就有負面影響;另外,根據在中國進行的一篇研究,室內生活型態的孩童,每天有戶外活動時,近視風險顯著降低。
  
  荷蘭鹿特丹Erasmus醫學中心博士候選人、Utrecht應用科技大學視力矯正與驗光科、前述荷蘭研究的第一作者Jan Roelof Polling表示,即使是年輕的視力正常兒童,花在戶外的時間和近距離作業的時間都與視軸長度有關。
  
  他們發現,每天在戶外時間少於45分鐘的孩童,每天近距離作業以及使用電腦超過2小時的孩童,視軸最長。
  
  Polling在視力與眼科研究協會2014年會中發表「Generation R」研究的結果。
  
  對6,690名各種族孩童,在6歲時進行視力與視軸長度檢查。這些孩童的整體近視盛行率是1.9%,荷蘭孩童是0.9%,非西方移民孩童達3.2%,視軸長度中位數是22.35 mm (範圍19.27-25.05 mm)。
  
  其中4,059名孩童有完成關於戶外活動時間的問卷,相較於每天戶外活動時間大於2小時的孩童,每天戶外活動時間小於1小時孩童的視軸長度顯著較長(22.41 vs 22.33 mm;P< .001)。
  
  此外,相較於每天戶外活動時間大於2小時的孩童,每天戶外活動時間小於1小時孩童之視軸長度大於平均值的風險達34%以上(勝算比1.34;95%信心區間1.14- 1.58)。
  
  視軸長度和長時間近距離作業之間的關聯並不顯著(P= .14),不過,Polling報告指出,探討曝露值四分位數與近距離作業的多變項分析發現,有顯著趨勢。
  
  他解釋,兩種因素對於眼睛發育各有影響。近視風險增加之孩童(例如家人有近視者),即便他們還很小,應鼓勵他們每週至少有15小時在戶外,避免長時間近距離作業。
  
  在這場研討會中,另一篇3年縱向研究也提到近視和花在戶外時間的關聯,這篇在中國廣州進行的研究包括了12所小學、超過2,000名的一年級孩童。
  
  東亞的近視率特別高;研究者將這歸因於孩童的家庭作業要求嚴格所致,讓他們得待在室內專注於需近距離完成的作業。
  
  這些學童被隨機分組,每天45分鐘戶外活動或維持一般作息;在開始時,戶外組和對照組的近視和等效球鏡度數盛行率相當。3年後,戶外組的近視盛行率顯著低於對照組(30.4% vs 39.5%; P < .001)。
  
  研究者結論指出,這些結果證明,透過學校增加學童的戶外活動時間量,可減少發生近視的孩童人數。
  
  澳洲坎培拉澳洲國立大學生物研究院、第一作者Ian Morgan博士解釋,這篇研究附屬於一項減少近視的公眾教育活動。
  
  Morgan博士解釋,增加戶外活動時間的公衛介入效果不錯,但是在東亞,必須相當程度地減少家庭作業量才可能,家庭作業多是學童沒有足夠戶外活動時間的主要因素。
  
  目前還不清楚戶外活動和近視之關聯的機轉,但是Morgan博士提出兩個主要懷疑 —多巴胺和曝露於紫外光(UV),他表示,動物研究的證據有利於光線/多巴胺假設,但是需要臨床試驗來解決這個議題。
  
  不過,他解釋,流行病學研究難以區分釋放多巴胺和增加UV曝露的影響程度,因為在戶外時,會曝露於更多光線、更多UV,也會釋放更多多巴胺。
  
  會議主持人、俄亥俄州立大學眼科學院Donald Mutti博士表示,這篇研究提供了孩童近視盛行率的證據;這篇研究不錯,對近視盛行率高的這些人,以縱向研究方式再度證明戶外活動對於發生近視有保護效果。
  
  Mutti博士表示,這篇研究和我們以前的研究結果一致(Invest Ophthalmol Vis Sci. 2012;53:7169-7175),花在戶外的時間對發生近視有某程度的保護效果,但是孩童一旦發生近視,則對其病程影響不大。
  
  他指出,Polling等人的研究貢獻在於,證明戶外活動對視力正常孩童的影響。
  
  這篇研究證明戶外活動時間對於幼童的視軸長度有影響。
  
  Mutti博士表示,近視和更嚴重的眼科疾病風險增加有關,包括青光眼,白內障和視網膜剝離,而近視本身對公衛也有重大影響。
  
  他表示,即使眼睛健康,消費者和保險公司每年在診斷和處理屈光度的財務負擔達數十億美元,在美國和全世界,未矯正的屈光度是可矯正之視力障礙的主因。
  
  資料來源: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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