Children in SG less exposed to outdoor light than Australians
Children in Singapore were exposed to significantly less outdoor light daily than children in Australia, which could contribute to the higher prevalence of myopia among Singapore children compared with their Australian counterparts, suggests a study.
“These differences equate to approximately 5 hours more outdoor light exposure per week … in the Australian children (~12 hour/week), on average compared with Singapore children (~7 hour/week),” said the researchers.
On average, Australian children experienced 44 minutes more exposure to daily outdoor light of >1,000 lux, as measured using a wearable light sensor, than their Singapore counterparts (mean duration, 105 vs 61 minutes/day; p=0.005). [Transl Vis Sci Technol 2018;doi: 10.1167/tvst.7.3.8]
Apart from outdoor time, the pattern of light exposure was also different between Australian and Singapore children, with larger differences seen on weekdays than weekends. On weekdays, children in Australia were exposed to 55 minutes more outdoor light daily than children in Singapore (p=0.001). Outdoor light exposure was 32 minutes greater in Australian vs Singapore children on weekends (p=0.04).
“Children in Singapore are more indoor-centric and spend less time outdoors on both weekdays and weekends compared with Australian children,” said the researchers.
Although both Australian and Singapore children had greater exposure to outdoor light on weekends than weekdays, children in Australia had >10 minutes exposure hourly across all time points on weekends compared with <10 minutes exposure hourly in Singapore children.
Children in both countries also had significantly greater exposure to outdoor light during school hours than outside of school hours. Outdoor light exposure during school hours accounted for 59 percent of exposure on weekdays for Australian children and 53 percent of that for Singapore children, with Australian children having 37 minutes more exposure per day during school hours than their Singapore counterparts (p<0.004).
“The relatively low levels of outdoor exposure observed in the Singaporean children during school hours further suggests there is significant scope for interventions to increase outdoor light exposure during school time,” said the researchers, suggesting activities such as conducting morning assembly or classes outdoor, increasing the number physical education outdoor, and promoting outdoor playtime during recess.
As low exposure to ambient light during childhood has been associated with faster eye growth, which could lead to myopia, the researchers stratified the analysis based on refractive status. [Invest Ophthalmol Vis Sci 2015;56:3103-3112] They found that myopic children in Australia were significantly less exposed to outdoor light by 34 minutes compared with non-myopic children (p=0.02). In contrast, there was no significant difference between myopic and non-myopic children in Singapore (p=0.27).
“It is worth noting that on average, the myopic children in Australia spent greater time per day exposed to outdoor light than both the myopic and non-myopic Singaporean children,” the researchers pointed out.
“Given the well documented, greater prevalence of myopia of Singaporean children, and the potential role of light exposure in myopia development, these findings provide valuable data to inform future implementation of school- and community-based outdoor programmes in urban Asian countries,” they added.