Toronto, Jul 2 (IANS): People aged 65 years and above who live in warmer regions are more likely to have serious vision impairment than their peers living in cooler regions, warned a study on 1.7 million old people living in different American counties.

Compared to those who lived in areas with average temperature of less than 10 degrees Celsius, the odds of severe vision impairment were 14 per cent higher for those who lived in areas with average temperature from 10-12 degrees Celsius, 24 per cent higher for those between 12 and 15.55 degrees Celsius and 44 per cent higher for those in counties with average temperature at 15.5 degrees Celsius or above.

"This link between vision impairment and average county temperature is very worrying if future research determines that the association is causal," said first author Professor Esme Fuller-Thomson, from University of Toronto.

"With climate change, we are expecting a rise in global temperatures. It will be important to monitor if the prevalence of vision impairment among older adults increases in the future," she added.

Further, the study, published in the journal Ophthalmic Epidemiology, found that the relationship between average temperature and severe vision impairment was strong regardless of age, sex, income, and education of participants. The association between higher county temperature and serious vision impairment was stronger for individuals aged 65 to 79 compared to those 80 or older, males compared to females. The observed link between average temperature and severe vision impairment may be strong, but the mechanism behind this relationship remains a mystery.

"We know that vision problems are a major cause of disabilities and functional limitations," said another co-author ZhiDi Deng, a pharmacy graduate from the University of Toronto.

"Serious vision impairment, for example, can increase the risk of falls, fractures, and negatively impact older adults' quality of life. Taking care of vision impairments and their consequences also cost the US economy tens of billions each year. So, this link between temperature and vision impairment was quite concerning," Deng said.

The team analysed 1.7 million community-dwelling and institutionalised older adults and compared their vision health with average temperature data obtained from the National Oceanic and Atmospheric Administration.