Low alcohol consumption associated with decreased odds of developing diabetic retinopathy: Study
While alcohol consumption in general is a significant risk factor for morbidity and mortality, moderate alcohol intake has demonstrated certain protective effects on cardiovascular diseases and diabetes mellitus (DM) status. Given that alcohol consumption is protective against developing DM, it is possible that alcoholic beverage intake might also influence the incidence and progression of DM complications, such as diabetic retinopathy (DR), a common and potentially blinding microvascular complication of DM. As the prevalence of DR is set to increase exponentially over the coming years, particularly in Asian populations, it is an important public health issue to determine the effects of alcohol consumption on the risk of development and progression of DR in Asians.
In this study, Gupta P et al examined the longitudinal association of baseline alcohol intake and frequency of alcohol intake with the 6-year incidence and progression of DR in a population-based cohort of Singaporean Indians with DM.
Study included 656 participants with diabetes mellitus, gradable retinal photographs from baseline (2007–2009) and follow-up (2013–2015) examinations, information on alcohol intake and other relevant data from the Singapore Indian Eye Study.
Incident DR was defined using the Modified Airlie House Classification as no DR at baseline and at least minimal non-proliferative DR at follow-up; and DR progression as at least a one-step worsening in DR at follow-up from minimal or worse status at baseline, excluding those with proliferative DR.
Alcohol intake was assessed as part of the sociodemographic questionnaire. Participants were asked if they currently drink alcohol (no, yes), and consumption frequency was quantified according to the following categories: (never; 1–2, 3–4 or 5–6 days per week and every day). Infrequent and frequent alcohol consumption were defined as ≤2and >2 days of alcohol intake per week, respectively.
The mean age (SD) of participants (n=656) was 58.8 (9.2) years, and 54.4% were male. At follow-up, 82 of 510 (16%) participants developed DR, and 45 of 146 (30.8%) had DR progression. 65 (12.7%) and 28 (19.1%) participants consumed alcohol in incident DR and progression categories, respectively.
In multivariable analyses, those who consumed alcohol had nearly two-thirds reduced odds of incident DR (OR (95% CI): 0.36 (0.13 to 0.98)) compared with those who did not. Participants with infrequent consumption of alcohol also had a reduction in odds of incident DR (0.17 (0.04 to 0.69)), compared with non-drinkers. No association was found between alcohol consumption and DR progression.
There are several biological mechanisms through which alcohol may have a protective effect for DR, supporting the plausibility of findings. Moderate alcohol intake, particularly of wine, has been regarded as a protective factor for cardiovascular events. As CVD is an important risk factor for DR, the benefit of wine intake might arise from the reduction of CVD risk. Increased inflammation and oxidative stress are the key pathological mechanisms in the development of DR. Alcohol has a high polyphenolic content, which contains anti-oxidants that combat sustained oxidation. Furthermore, polyphenols inhibit angiogenesis; prevent inflammation and facilitate vaso-relaxation, all of which result in increased blood flow in the retina and counteract the reduced blood flow resulting from DR.
In this population-based cohort study of Asian participants with DM, authors demonstrated that, compared with abstainers, alcohol consumption and infrequent alcohol intake (≤2days/week) lowered the odds of incident DR in a population-based cohort of Indian Singaporeans. However, alcohol consumption was not associated with DR progression. The findings suggests that a drinking pattern of low alcohol consumption per week may be protective of the development of DR in people with DM. These findings may assist clinicians in making evidence-based dietary and beverage recommendations when counselling patients with DM who are at risk of DR.
Further longitudinal and experimental studies are needed to confirm the findings and determine underpinning mechanisms.
Source: Gupta P, et al. Br J Ophthalmol 2020;0:1–5.