Lifestyle factors modify vision impairment risk

By Lucy Piper, Senior medwireNews Reporter

Smoking, drinking alcohol and physical activity are modifiable behaviours that influence the risk of vision impairment (VI), show findings from the Beaver Dam Eye Study.

The researchers calculated, for example, that women with early age-related macular degeneration (AMD) and an annual household income less than US$ 10,000 would have an estimated 20-year cumulative incidence of VI of 5.9% if they drank occasionally and were physically active, compared with 25.8% if they consumed no alcohol and were sedentary.

With the number of people with VI increasing as a result of an ageing population, the researchers highlight the importance of identifying risk factors that could be modified with intervention to decrease the burden.

Led by Ronald Klein (University of Wisconsin-Madison School of Medicine and Public Health, USA), the team measured the best-corrected visual acuity (BCVA) of 4926 people aged 43 to 86 years in 1988 to 1990, who were reassessed at approximately 5-yearly intervals over a period of 20 years.

The 20-year cumulative incidence of VI, based on a BCVA in the better-seeing eye of less than 20/40, was 5.4%, and the resulting loss of letters over this period was 6.6.

Both the number of letters lost and the incidence of VI increased with age. After adjusting for this as well as income and AMD severity, being a current or past smoker was associated with a significant increase in the number of letters lost.

Indeed, within each 5-year interval, current smokers lost at least 0.45 letters more than did never smokers, the researchers report in Ophthalmology.

Smoking was no longer significantly associated with the risk of developing visual impairment after controlling for confounding factors, but physical activity was. Participants who consumed no alcohol were 2.12 times more likely to develop VI than those who had drank less than one alcoholic beverage per week in the past year. The researchers note that the amount of alcohol consumed had little effect, with the risk reduction similar for those consuming less than one alcoholic beverage per week as for those consuming one or two drinks per day.

Physical activity also influenced the risk of VI, reducing the likelihood by approximately 60% compared with a sedentary lifestyle.

The researchers note that there were some differences in the strength of the associations between men and women, but the directions were the same.

“It remains to be seen whether changes in these factors will result in fewer incident cases of VI in the aging population”, they conclude.

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