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Alcohol consumption affects risk of cataracts

 Authors’ Abstract
Purpose: To assess whether alcohol consumption is associated with the long-term incidence of cataract or cataract surgery.
Design: Population-based prospective cohort study.
Methods: A total of 3,654 persons aged 49+ years were examined at baseline and 2,564 were re-examined after 5 and/or 10 years.  Lens photographs were taken at each visit and assessed using the Wisconsin Cataract Grading System by masked graders.  An interviewer-administered questionnaire was used to collect information on alcohol consumption.
Results: No significant associations were observed between alcohol consumption and long-term risk of nuclear, cortical, and posterior subcapsular cataract.  However, after adjusting for age, gender, smoking, diabetes, myopia, socioeconomic status, and steroid use, total alcohol consumption of over 2 standard drinks per day was associated with a significantly increased likelihood of cataract surgery, when compared to total daily alcohol consumption of 1 to 2 standard drinks (adjusted odds ratio [OR] 2.10, 95% confidence interval [CI] 1.16-3.81).  Abstinence from alcohol was also associated with increased likelihood of cataract surgery when compared to a total alcohol consumption of 1 to 2 standard drinks per day (adjusted OR 2.36, 95% CI 1.25–4.46).
Conclusion: A U-shaped association of alcohol consumption with the long-term risk of cataract surgery was found in this older cohort: moderate consumption was associated with 50% lower cataract surgery incidence, compared either to abstinence or heavy alcohol consumption.
International Scientific Forum on Alcohol Research comments
This is an interesting paper that deals with a common medical condition that will continue to be of great importance with the ageing of the population.
Background:  Few longitudinal studies have dealt with cataracts, with the Beaver Dam Eye Study (BDES)1 the only one prior to the present one that has been population based.  BDES found little relationship between alcohol and cataracts, although there was some evidence for a U-shaped curve with posterior subcapsular cataracts.
Among other cohort studies, the Nurses’ Health Study2 found little evidence of an effect of alcohol intake on the risk of surgery for cataracts.  Their data are compatible with a slight decrease in risk of total cataracts with light drinking (up to 14.9 g/day) and an increased risk for certain types of cataract with greater amounts of alcohol.  An earlier report from the Physician’s Health Study3 reported no significant effect of alcohol, although there was a trend towards increased risk of certain types of cataracts with greater alcohol intake.
Comments on the present study:  The strengths include the analyses being based on a population-based cohort with excellent recruitment and good retention of subjects, and repeated eye examinations with excellent ascertainment of cataracts.  The investigators had blinded assessments of lens photographs for the objective diagnosis of cataracts.  Weaknesses that limit the information presented relate to the choice of the category with 1-2 drinks/day as the referent group, as there were very few subjects reporting consumption at this level.  (For example, there were only 4 subjects with posterior subcapsular cataracts in the referent group consuming wine and 8 in the referent group for beer.)  The paper does include in the text the associations between alcohol and cataract surgery using nondrinkers as the referent group, and state that “persons reporting moderate alcohol consumption (1-2 drinks/day) had a significantly reduced incidence of cataract surgery (OR 0.47, 95% CI 0.26-0.85),” but data are not presented for the lighter drinkers.
One would assume that data on the development of cataracts would be more objective and informative than on the occurrence of cataract surgery, as the latter may be related to many other socio-economic factors.  (On the other hand, the associations generally changed very little when the age-gender-adjusted rates are compared with the fully adjusted models that included socio-economic status.)
It is unfortunate that the authors chose to not include in their paper the results of multivariable-adjusted analyses for many categories, since the “dose-response” pattern is often more informative than the statistical significance of any one cell.  In other words, if odds ratios of cataracts are lower in both the non-drinkers and the heavier drinkers than among the moderate drinkers, it would suggest a “U-shaped” association.  The conclusions of the authors are apparently based exclusively on statistical results and tend to not describe the pattern of effect for each beverage and total alcohol.
References from Forum Review
1.  Koppes LL, Dekker JM, Hendriks HF, et al. Moderate alcohol consumption lowers the risk of type 2 diabetes: a meta-analysis of prospective observational studies. Diabetes Care 2005;28:719–725.
2.  Carlsson S, Hammar N, Grill V. Alcohol consumption and type 2 diabetes.  Meta-analysis of epidemiological studies indicates a U-shaped relationship. Diabetologia 2005;48:1051–1054.
3.  Baliunas DO, Taylor BJ, Irving H, et al. Alcohol as a risk factor for type 2 diabetes: a systematic review and meta-analysis. Diabetes Care 2009;32:2123–2132.
Comments included in this critique by the International Scientific Forum on Alcohol Research were provided by the following:
Erik Skovenborg, MD, Scandinavian Medical Alcohol Board, Practitioner, Aarhus, Denmark
Ross McCormick PhD, MSC, MBChB, Associate Dean, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
Harvey Finkel, MD, Hematology/Oncology, Boston University Medical Center, Boston, MA, USA
R. Curtis Ellison, MD, Section of Preventive Medicine & Epidemiology, Boston University School of Medicine, Boston, MA, USA
Roger Corder, PhD, MRPharmS, William Harvey Research Institute, Queen Mary University of London, UK

Source: Alcohol consumption affects risk of cataracts. Kanthan GL, Mitchell P, Burlutsky G, Wang JJ.  Alcohol Consumption and the Long-Term Incidence of Cataract and Cataract Surgery: The Blue Mountains Eye Study.  Am J Ophthalmol 2010;150:434–440.

 

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