Snellen chart. Originally developed by Dutch ophthalmologist Herman Snellen in 1862, to estimate visual acuity.

A new research study published in the journal Ophthalmic Epidemiology shows that American adults aged 65 or older who live in warmer regions are more likely to have serious vision problems compared to those living in cooler areas.

According to the study, those who live in counties with an average temperature of less than 50°F (<10 °C) have a lower chance of severe vision impairment compared to those who live in counties with an average temperature between 50-54.99°F. The odds of severe vision impairment increase by 14% for those in the 50-54.99°F range, 24% for those in the 55-59.99°F range, and 44% for those in counties with an average temperature of 60°F (15.5 °C) or higher.

First author Professor Esme Fuller-Thomson, said,

“This link between vision impairment and average county temperature is very worrying if future research determines that the association is causal. 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.”

Co-author ZhiDi Deng, a recent pharmacy graduate from the University of Toronto, added,

“We know that vision problems are a major cause of disabilities and functional limitations. 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.”

Impact of age, sex, income, and education

The relationship between average temperature and severe vision impairment was consistently strong across all demographic factors, including age, sex, income, and education of participants. Elysia Fuller-Thomson, a graduate student at the University of Toronto and co-author of the study, notes that the link between vision impairment and temperature remained consistent across all income levels.

Among those aged 65-79, males, and White Americans, the association between higher county temperature and serious vision impairment was stronger compared to those 80 or older, females, and Black Americans, respectively.

Causes remain a mystery

The mechanism behind this relationship between higher average temperature and severe vision impairment is still unknown. The study’s authors have suggested several possible causes for this link, including increased exposure to ultraviolet light, air pollution, infections, and folic acid degradation with increased temperature. However, the study’s design does not offer definitive insight into how temperature affects vision.

The study analyzed data from six consecutive waves of the American Community Survey (2012-2017), which surveyed a nationally representative sample of American respondents aged 65 and older annually. The sample included 1.7 million older adults living in the contiguous US who lived in the same state in which they were born and were either living in the community or in an institution. The survey asked respondents whether they were blind or had serious difficulty seeing, even when wearing glasses. The researchers combined this data with average temperature data obtained from the National Oceanic and Atmospheric Administration.

Esme Fuller-Thomson, said:

“We were very surprised to discover this strong association between temperature and vision impairment. But this novel finding introduces more questions than it answers, including what the connection between average county temperature and vision impairment is. Moving forward, we plan to investigate whether county temperature is also associated with other disabilities among older adults such as hearing problems and limitations in daily activities.”

Image Credits

In-Article Image Credits

Snellen chart. Originally developed by Dutch ophthalmologist Herman Snellen in 1862, to estimate visual acuity. via Wikimedia Commons by Jeff Dahl with usage type - Creative Commons License. July 23, 2008