A new study published in Ophthalmic Epidemiology led by a team of researchers from the University of Toronto assessed the relationship between serious visual impairment and average regional temperature in older Americans.
How was this assessed?
A cross-sectional analysis used responses from the American Community Survey (ACS) from 6 consecutive years (2012-2017) to measure the potential connection.
Additionally, the average annual temperature from the National Oceanic and Atmospheric Administration was combined into a 100-year average and mapped to the corresponding US Census Bureau’s public use microdata areas from the ACS.
Tell me more.
The analyzed subsample included 1,707,333 community-dwelling and institutionalized elderly adults aged 65 and older in the US who lived in the same state where they were born.
The question that addressed severe vision impairment was, “Is this person blind, or does he/she have serious difficulty seeing even when wearing glasses?”
Findings?
The study authors noted that a higher average temperature was consistently associated with increased odds of severe vision impairment across all cohorts, such as age, sex, race, income, and educational level.
Give me examples.
The odds of severe vision impairment were 14% higher for elderly adults who lived in counties with average temperatures between 50 and 54.99°Fahrenheit (F) and 24% higher for those between 55 and 59.99°F.
Compared to elderly adults who lived in counties with an average temperature of <50°F, the odds of severe vision impairment were 44% higher in counties with an average temperature of 60°F or above (odds ratio 1.44, 95% confidence interval 1.42-1.46).
Any other connections?
The association between higher county temperature and serious vision impairment was stronger for individuals aged 65-79 compared to those 80 or older, males compared to females, and white Americans compared to Black Americans.
So what causes this?
Investigators speculated that increased ultraviolet light exposure, air pollution, infections, and folic acid degradation with increased temperature could explain the relationship between severe vision impairment and hotter climates.
However, they noted that the exact mechanism linking the two is still currently unclear.
Expert opinion?
According to ZhiDi Deng, co-author of the study, the investigators determined that vision problems are a major cause of disabilities and functional limitations. “Serious vision impairment, for example, can increase the risk of falls and fractures and negatively impact older adults’ quality of life,” Deng stated. “Taking care of vision impairments and their consequences also cost the US economy tens of billions each year.”
What’s the big picture?
While further studies are required to evaluate if this relationship between severe vision impairment and temperature is causal, as global temperatures are expected to rise, the findings from this study are worrying.
The predicted rise in global temperatures could impact the number of elderly Americans affected by severe vision impairment and, by extension, the associated health and economic burden.
So what’s next?
The next step for the research team will be investigating whether county temperature is linked with other disabilities in older adults, including hearing problems and limitations in daily activities.