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Study: Higher average temperature linked to serious vision impairment among older Americans


In a study of 1.7 million older Americans by a team of researchers from the University of Toronto, those living in counties with an average temperature of 60°F or above had an increased chance of suffering serious vision impairment than those in cooler counties.

a thermometer that shows the temperature is very hot with the sun beating down. (Image Credit: AdobeStock/vladischern)

(Image Credit: AdobeStock/vladischern)

A recent study by a team of University of Toronto researchers found that American adults 65 years old and older living in warmer regions are more likely to have serious vision impairment than their peers living in cooler regions.1

According to a University of Toronto news release, when compared to individuals who lived in counties with average temperature of less than 50°F (< 10 °C), the risks of severe vision impairment were 14% higher for those who lived in counties with average temperature between 50-54.99°F, 24% higher for those between 55-59.99°F and 44% higher for those in counties with average temperature at 60°F (15.5 °C) or above.

Esme Fuller-Thomson, PhD, lead author of the study, noted in the release the 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,” Fuller-Thompson said in a statement. “It will be important to monitor if the prevalence of vision impairment among older adults increases in the future.”

Fuller-Thomson is the director of University of Toronto’s Institute of Life Course and Aging and is a Professor in the Factor-Inwentash Faculty of Social Work and the Department of Family and Community Medicine.

ZhiDi Deng, PharmD, a recent pharmacy graduate from the University of Toronto, noted in the release it is documented 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,” Deng said in the release. “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 strong regardless of age, sex, income, and education of participants.

“It was powerful to see that the link between vision impairment and temperature was consistent across so many demographic factors including income.” co-author Elysia Fuller-Thomson, a graduate student at the University of Toronto, said in the university’s news release.

Moreover, connections between higher county temperature and serious vision impairment proved to be greater for individuals aged 65 to 79 compared to those 80 or older, males compared to females, and White Americans compared to Black Americans, researchers noted in the news release.

Causes remain a mystery

The researchers noted the observed link between average temperature and severe vision impairment may be strong, but the mechanism behind this relationship remains a mystery.1

On top of that, the researchers hypothesize several potential causes for the observed relationship, including increased ultraviolet light exposure, air pollution, infections, and folic acid degradation with increased temperature. However, the design of this study does not provide definitive insight into how temperature affects vision, the university noted.

According to the news release, the study was based on 6 consecutive waves of the American Community Survey (2012 to 2017) which surveyed a nationally representative sample of American respondents aged 65 and older annually. The sample analyzed included 1.7 million community-dwelling and institutionalized older adults in the coterminous US who lived in the same state in which they were born.

Moreover, according to researchers, the question on vision impairment was “Is this person blind or does he/she have serious difficulty seeing even when wearing glasses?” The news release noted the average temperature data was obtained from the National Oceanic and Atmospheric Administration and combined with data from the American Community Survey.

Esme Fuller-Thomson pointed out in the release the research team was 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,” Fuller-Thompson concluded in the news release. “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.”

  1. Esme Fuller-Thomson, PhD, ZhiDi Deng, PharmD, Elysia G. Fuller-Thomson B.Sc. Association Between Area Temperature and Severe Vision Impairment in a Nationally Representative Sample of Older Americans, Ophthalmic Epidemiology, Published June 20, 2023. DOI: 10.1080/09286586.2023.2221727
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