Summary: American seniors residing in warmer regions are more likely to suffer from severe vision impairment compared to their counterparts in cooler areas.
The odds of serious vision impairment increased incrementally with the rise in average temperature, with a 44% higher risk for those living in regions averaging 60°F or above. The correlation remained consistent regardless of age, sex, income, and education.
The exact cause behind the association is yet to be identified, sparking concerns amid rising global temperatures.
Seniors residing in regions with an average temperature of 60°F (15.5 °C) or above had a 44% higher risk of serious vision impairment compared to those in areas with an average temperature of less than 50°F (< 10 °C).
The association between higher average temperature and severe vision impairment was consistent across various demographic factors such as age, sex, income, and education.
The exact cause behind the observed relationship between temperature and vision impairment remains unknown, raising concerns in the context of global warming.
Source: University of Toronto
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, according to a recent study published in the journal Ophthalmic Epidemiology.
Compared to those who lived in counties with average temperature of less than 50°F (< 10 °C), the odds 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.
“This link between vision impairment and average county temperature is very worrying if future research determines that the association is causal” says first author Professor Esme Fuller-Thomson.
“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.” Dr. 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.
“We know that vision problems are a major cause of disabilities and functional limitations,” says co-author ZhiDi Deng, a recent 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.”
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.” says co-author Elysia Fuller-Thomson, a graduate student at the University of Toronto.
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, and White Americans compared to Black Americans.
Causes remain a mystery
The observed link between average temperature and severe vision impairment may be strong, but the mechanism behind this relationship remains a mystery.
The study’s authors 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 study was based on 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 analysed 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.
The question on vision impairment was “Is this person blind or does he/she have serious difficulty seeing even when wearing glasses?” Average temperature data was obtained from the National Oceanic and Atmospheric Administration and combined with data from the American Community Survey.
“We were very surprised to discover this strong association between temperature and vision impairment,” says Esme Fuller-Thomson.
“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.”
Association between area temperature and severe vision impairment in a nationally representative sample of older
Several small studies have associated exposure to elevated average temperature with specific vision problems. However, no large-scale studies have examined the relationship between vision impairment and average area temperature in the general population. We conducted a cross-sectional analysis of a large nationally representative sample of older adults to further explore this relationship.
Secondary analysis of the American Community Survey (ACS). The survey was conducted through mail, telephone and in-person interviews. Data from six consecutive years of the cross-sectional survey were analysed (2012–2017). The subsample analysed included community-dwelling and institutionalized older adults aged 65 and older in the coterminous US who lived in the same state in which they were born (n = 1,707,333). The question on severe vision impairment was “Is this person blind or does he/she have serious difficulty seeing even when wearing glasses?”. Average annual temperature data from the National Oceanic and Atmospheric Administration was combined into a 100-year average and mapped to corresponding US Census Bureau’s public use microdata areas from the ACS.
Higher average temperature is consistently associated with increased odds of severe vision impairment across all cohorts (i.e. age, sex, race, income, and educational attainment cohorts) with the exception of Hispanic older adults. Compared to those who lived in counties with average temperature of < 50 °F (< 10 °C) , the odds of severe vision impairment were 44% higher in counties with average temperature of 60 °F (15.5 °C) or above (OR 1.44; 95% CI 1.42–1.46).
If the association is found to be causal, the predicted rise in global temperatures could impact the number of older Americans affected by severe vision impairment and the associated health and economic burden.