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Thursday, 22 April 2021 08:01

Do moderate wine drinkers have a lower risk of cataract surgery?

Recent headlines have stated that moderate wine consumption may prevent cataracts. What are the practical implications/practical significance of these headlines?

 

What is it all about?

Age-related cataract is the leading cause of visual impairment worldwide. With an ageing population and a greater life expectancy, the number of individuals with cataract is likely to increase. A cataract is a clouding of the eye’s lens. It normally develops slowly and does not affect the vision at the beginning. However, over time and as the cloudiness of the eyes eventually progresses, it causes moderate to severe vision impairment and it becomes more difficult to read, drive a car or see clearly. The only available treatment for cataract is to surgically remove the lens of the eye and replace it with an artificial lens.

Identifying modifiable risk factors could thus help to delay surgery. Study results examining the moderate consumption of alcoholic beverages and cataract have been inconsistent. Some have been associated with less cataract and other found no relationship.

A large UK prospective study (with a long follow-up time between 8 and 16 years) examined the relationship between cataract surgery and the consumption of alcoholic beverages. For this purpose, the authors collected detailed health and lifestyle information of nearly 500,000 participants enrolled in two different study populations (EPIC-Norfolk and UK Biobank). Among many other things, they were asked via questionnaire about the amount, frequency, and type of alcoholic beverage they consumed.

 

Main findings:

In both study populations, the moderate drinkers were 10-11% significantly less likely to have a cataract surgery than non-drinkers (after controlling for health factors and socio-demographic factors).

  • Participants of the EPIC-Norfolk study

who consumed between 44 and 89 grams of alcohol/week and more than 89g/week, had a 14% and 18% lower risk to undergo cataract surgery.

  • The UK Biobank participants

who consumed alcoholic beverages 1-2 times per week and 3-4 times week (compared to those who drank 1-3 times or less per month), were 7% and 6% less likely to have cataract surgery. 

  • Moderate wine consumption

When examining the types of alcoholic beverages, the strongest protective effect was seen in moderate wine drinkers (up to approximately 6.5 glasses per week). They had the lowest risk to have a cataract surgery compared to those who abstained or who consumed other alcoholic beverages. This finding was consistent in these two independent studies. In the EPIC-Norfolk study, those who consumed wine in the low to moderate range were 23% less likely to have a cataract surgery than non-drinkers. Similar favorable results were observed for red and white wine drinkers in the UK Biobank study with a 14% lower risk.

 

It needs to be mentioned that the two studies used different measures of consumption and that the comparability of the two datasets may thus be limited:

Only the EPIC-Norfolk data provided the amount for the total intake of alcoholic beverages (grams per week) whereas the UK Biobank data reported on the frequency of consumption.

--> Despite these differences in measuring the intake of alcoholic beverages, both studies had similar results providing some evidence of the robustness of the observed effect.

 

It is not possible to determine, if the observed protective association of wine intake on cataract surgery is causal.

--> However, the observed dose-response among drinkers - which means a reduced likelihood to require cataract surgery with a progressively increasing intake of wine/alcoholic beverages (only up to moderate levels) - contributes some evidence.

 

What are the practical implications of these results?

The authors concluded that there was a small but significant lower risk of cataract surgery among moderate drinkers. Red and white wine consumers showed more consistent and significant lower risks of cataract surgery than consumers of other alcoholic beverages.

As a possible explanation of the observed protective advantage of wine, the researchers explained that cataract development may be due to gradual damage from oxidative stress during ageing. Their results showed a better protection among wine drinkers and this may suggest a protective role of the wine polyphenols. Polyphenols are powerful plant compounds that have antioxidant properties and are especially abundant in red wine.

However, while this explanation makes sense biologically, other dietary factors may also play a role and have not been integrated in the data analysis of the current study. In terms of drinking pattern, no information was given on whether the wine was consumed with or without food.

It is important to consider the context, such as dietary and drinking patterns, and not only focus on one factor. Thus, it is not possible to determine, if the observed protective association of wine/alcohol intake on cataract surgery is causal and more studies are required to examine this association.

 

Chua SYL, Luben RN, Hayat S, Broadway DC, Khaw KT, Warwick A, Britten A, Day AC, Strouthidis N, Patel PJ, Khaw PT, Foster PJ, Khawaja AP; UK Biobank Eye and Vision Consortium. Alcohol Consumption and Incident Cataract Surgery in Two Large UK Cohorts. Ophthalmology. 2021 Feb 8:S0161-6420(21)00114-7. doi: 10.1016/j.ophtha.2021.02.007. Epub ahead of print. PMID: 33571551. https://www.aaojournal.org/article/S0161-6420(21)00114-7/fulltext

For more information about this article, read the scientific abstract here.

 

 

Definitions:

EPIC-Norfolk (18 646 alcohol consumers):

Quartiles of total weekly alcohol intake

Lowest intake                             ≤ 14.1 g of alcohol/week (reference)

Quartile 2                                   14.23-43.7 g of alcohol/week

Quartile 3                                   44-89 g of alcohol/week

Highest intake                             ≥ 89 g of alcohol/week  

 

1 unit of alcohol = 8 grams which is equivalent to 1 glass of wine, half a pint of beer or 1 single measure of spirits.

 

UK Biobank (432 260 alcohol consumers):

Frequency of alcohol consumption

1-3 times or less per month                    

1-2 time per week

3-4 times per week

Daily or almost daily