Indian migrants in Singapore plagued by diabetic retinopathy
Migrant Indians living in Singapore are twice as likely to have diabetic retinopathy (DR) than their counterparts in Urban India, according to a recent study.
The study included 759 adult Indian diabetics (mean age 59.24±9.4 years; 53.23 percent male) who participated in the baseline (2007–2009) and follow-up (2012–2015) cycles of the Singaporean Indian Eye Study. The modified Airlie House Classification was used to grade retinal photographs for the presence and severity of DR.
Most of the participants (n=501) did not have DR at baseline. Of these, 93 developed DR over the 6-year follow-up period, resulting in an age-standardized incidence rate of 21.89 percent. Minimal DR was the most common stage (55.91 percent), followed by mild (24.73 percent) and moderate (16.13 percent) DR. Thirty-eight participants developed DR in both eyes. [Br J Ophthalmol 2019;doi:10.1136/bjophthalmol-2018-313282]
At baseline, 189 patients were positive for DR and were thus included in the progression analysis. Disease progressed in 29.6 percent (n=56) over the 6-year follow-up period. Twenty-nine cases worsened from questionable at baseline to moderate DR after 6 years. Thirteen and 14 cases progressed to mild and vision-threatening DR, respectively.
The resulting age-standardized incidence rate of DR progression was 33.45 percent.
“When compared with Indians living in Urban India, DR incidence and progression were found to be higher in Singapore Indians,” said researchers, noting that the respective literature rates were 9.25 percent and 12.61 percent. [Ophthalmic Epidemiol 2017;24:294-302]
“This discordance may be due to either shorter follow-up period (4-year vs 6-year) or use of simpler DR grading scale (International Clinical Diabetic Retinopathy Severity Scale),” they added. The presence of more systematic screening programmes in Singapore may have also contributed to this difference.
Changes in environment and living conditions may also explain these discrepancies, researchers explained. “[M]igrant Indians in Singapore experience new lifestyle patterns and dietary habits with calorie-dense/low-fibre foods that make tight diabetes control difficult to attain leading to increased development and progression of DR.”
Indeed, multivariable-adjusted regression models showed that glycaemic control, as measured by levels of glycated haemoglobin (HbA1c), is a significant predictor of DR incidence (relative risk [RR], 1.41; 95 percent CI, 1.28–1.55; p<0.001). Other lifestyle and associated factors also showed significant correlations, such as current smoking (RR, 1.63; 1.02–2.62; p=0.041) and body mass index (BMI; RR, 0.74; 0.6–0.93; p=0.009).
For DR progression, significant risk factors included HbA1c (RR, 1.26; 1.13–1.42; p<0001) and BMI (RR, 1.26; 1.02–1.56; p=0.033).
“In addition, mild and moderate levels of DR progressed despite mean HbA1c levels showing slight reduction at follow-up visit from baseline visit,” said researchers. “This could be attributable to the ‘legacy’ effect or a ‘metabolic memory’ phenomenon, where DR continues to progress even after hyperglycaemic insult is replaced by a normal glycaemic phase.”
However, “[t]he risk factors identified in our models are unable to fully explain the risk of incidence and progression of DR. Several biomarkers are currently being explored that may provide additional risk information,” they added. Future studies exploring less-invasive biomarkers and employing more advanced techniques will contribute to this end.