Findings from a retrospective study of children in Australia suggest myopia among disadvantaged Australian schoolchildren aged six to15 has doubled compared with 40 years ago, but continues to be significantly lower and refraction slightly more hyperopic than in other locations that include Australian urban areas.
The study findings suggests environmental factors, including socioeconomic status, education and outdoor activity, in addition to genetic propensity, influence the risk of myopia.
Published in Plos One, the authors demonstrated for the first time, “lower myopia prevalence and higher spherical equivalent refraction (SER) associated with socioeconomic disadvantage in Australia, particularly in a population of children from rural areas”.
They noted that geographical remoteness was associated with children spending more physically active time outdoors than children living in urban areas and conceivably spending less free time on digital devices and near tasks. Educational expectations and learning outcomes are higher for children living in urban regions, particularly in high density housing
The retrospective study analysed the clinical records of children who had attended Stewart House Children’s Charity on Sydney’s northern beaches. The Centre provides respite care with health screening and personal health and wellbeing education and support to children from disadvantaged populations. Most children who attend the Centre come from rural or remote areas of New South Wales and the Australian Capital Territory.
Among the 4585 children who consented to participate in an eye examination, the data of 4365 (95.2%) children were used for analysis. Two thirds of the children came from rural areas (socioeconomic status level five), and one third came from low-density housing in the outer suburbs of Sydney.
According to the authors, numerous studies have shown myopia prevalence is influenced by environmental factors, such as living in urban as opposed to rural areas, inner city-urban and outer suburban areas, population density and house size, and housing type. These new findings suggest other external factors, for example social disadvantage, also appear to impact myopia prevalence – children of parents with fewer years education and lower incomes are less likely to become myopic.
The overall prevalence of myopia, emmetropia and hyperopia were 4.0%, 51.6% and 44.3%, respectively.
Myopia prevalence increased gradually from 2.5% to 7.0%, at age six and seven, and 14 and 15, respectively. There was a corresponding increase in the prevalence of emmetropia from 38.0% to 54.8% (all P < 0.0001).
A decrease in prevalence of hyperopia was observed with age from 59.5% to 38.2% (P < 0.0001).
Across three time points 2014, 2016 and 2018, the prevalence of emmetropia increased from 33.3% to 57.8% and 64.9%, respectively (P < 0.001). In comparison, over the three years, hyperopia prevalence decreased from 63.2% to 37.8% and 30.9%, respectively (P < 0.001), and myopia prevalence was 3.5%, 4.4% and 4.3%, respectively.
There was no significant difference in the prevalence of myopia between three years (all P > 0.05). Multivariate regression analyses showed that the older the age, the higher the prevalence of myopia (OR = 1.20, 95% CI: 1.09~1.31, P = 0.0001), but the prevalence of myopia was not related to sex (OR = 1.10, 95% CI: 0.81~1.49, P = 0.53) or year of testing (P > 0.05, Table 3)
Reflecting Back 40 Years
The authors found prevalence of myopia had doubled when compared with findings from a similar study 40 years ago, but it remained significantly lower, and the refraction was slightly more hyperopic, than in other locations among schoolchildren of a similar age.
They wrote, “This study has demonstrated for the first time, lower myopia prevalence and higher spherical equivalent refraction (SER) associated with socioeconomic disadvantage in Australia, particularly in a population of children from rural areas. Geographical remoteness is associated with children spending more physically active time outdoors than children living in urban areas and conceivably spending less free time on digital devices and near tasks. Educational expectations and learning outcomes are higher for children living in urban regions, particularly in high density housing
“In conclusion, this study showed that the prevalence of myopia among disadvantaged Australian schoolchildren aged six to15 has doubled compared with 40 years ago amongst schoolchildren of a similar age, but it continues to be significantly lower and the refraction is slightly more hyperopic than in other locations including in Australian urban areas. This may suggest that reasons for the large increase in prevalence of myopia reported in other countries must include questions relating to environmental risk factors, in particular, socioeconomic status, education and outdoor activity in addition to genetic propensity.”
Aicun Fu, Kathleen Watt, Barbara M. Junghans, Androniki Delaveris, Fiona Stapleton. Prevalence of myopia among disadvantaged Australian schoolchildren: A 5-year cross-sectional study August 27, 2020, DOI: doi.org/10.1371/journal.pone.0238122