Diabetic retinopathy and macular oedema increase in Spain

Diabetic retinopathy and diabetic macular oedema are both increasing in Spain, especially among relatively young people, researchers said. 

“Our results suggest a greater number of ocular complications in the near future, such as neovascular glaucoma, if these current findings are not addressed,” wrote Pedro Romero-Aroca, and colleagues from University Rovira and Virgili in Reus, Spain.

They published their findings in the British Journal of Ophthalmology.

Related: Why primary angle-closure glaucoma is declining in Scotland

Diabetes mellitus is on the rise worldwide. In Spain, previous projections show an 11.1% increase in prevalence, reaching 3.886 million people by 2030. The disease can lead to diabetic retinopathy, a common cause of blindness in Europe.

Researchers have noticed a significant increase in the incidence of diabetic retinopathy since 2011. They noted increases in its severe forms and diabetic macular oedema, especially in young patients.

Researchers screened 15,396 Caucasian patients with diabetes mellitus over the course of eight years, with a mean of 3.18 visits. This was 86.53% of the 17,792 patients with diabetes mellitus who received care from general practitioners in 16 health care areas covered by the university medical centre.

Recent: How to optimimally treat rhegmatogenous retinal detachment

There were more men than women in the sample, which is typical of the prevalence of diabetes in the population as a whole.

The researchers found that the mean yearly incidence of any diabetic retinopathy remained stable from 2007 to 2011, when the incidence rate was 8.09%. From there, the rates began to climb with an incidence of 8.11% in 2011, 8.77% in 2012, 8.92% in 2013, and 8.99% in 2014.

Diabetic macular oedema

Likewise, the incidence of diabetic macular oedema rose slowly from 2% in 2007 to 2.08% in 2011, then somewhat more rapidly, reaching 2.49% in 2014.

Severe diabetic retinopathy also stayed more or less stable from 2007 to 2010, but rose from 0.57% in 2011 to 0.75% in 2014.

Proliferative diabetic retinopathy followed a similar trajectory. There was only one case in 2007 and another case in 2009. No other cases were reported until 2012 when there were four, followed by five in 2013, and eight in 2014.

Recent: Outer retinal layer thickness predicts visual acuity in diabetic macular oedema

The changes in all these conditions were statistically significant (P > 0.001).

“The increase in incidence of [diabetic retinopathy] over the last three years of our study is surprising,” they wrote.

In a previous cross-sectional study, these researchers found a decrease in the prevalence of diabetic retinopathy in type 2 diabetes mellitus from 39.41% in 1993 to 26.11% in 2007.

Studies in England, Wales, and Scotland with similar methodology showed a similar magnitude of incidence of retinopathy.

Recent: Endothelial keratoplasty on the rise in northwestern Italy

Other researchers had shown a decrease in diabetic retinopathy in type 1 diabetes mellitus, corresponding to better glycaemic control.

Analysing their data further, Romero-Aroca and colleagues were surprised to find that diabetic retinopathy had particularly increased among people 41 to 60 years of age. Patients 31 to 40 years of age also showed small but evident increases.

Likewise, the incidence of advanced diabetic retinopathy rose among patients 31 to 70 years of age.

Risk factors

To better understand the causes of this trend, researchers looked for risk factors, and identified male gender, long duration of diabetes, arterial hypertension, and bad metabolic glycaemia control (as evaluated by HbA1c levels and insulin treatment).

They found the age groups with higher levels of HbA1c were also the age groups with higher insulin treatment.

“For us, it was evident that the patients become more relaxed in their metabolic control of diabetes in these age groups, with a corresponding high percentage of ocular complications,” they wrote, adding that they are unsure of why this occurs.

Related: Latest concepts in steroid therapy for diabetic macular oedema

The researchers acknowledged some shortcomings of their study. For one, the statistical analysis of 8-year total incidence was not the same as the cumulative incidence because they did not screen all the patients with diabetes mellitus, either at baseline or at the final follow-up.

They also noted that the use of wide-field image techniques could have caused the severity scale to vary, increasing the number of patients counted as having advanced diabetic retinopathy.

Related: Two genetic discoveries offer hope for patients with advanced AMD

In addition, the number with proliferative diabetic retinopathy was small and might have biased the statistical analysis.

Finally, the researchers did not study the patients’ renal status as a risk factor for diabetic retinopathy because they didn’t have enough patients with that data available.

Strengths of the study include the large sample size and large number of visits per patient.

If other studies bear out these findings, Romero-Aroca and colleagues concluded, “we can expect in future that we will have to treat a lot of complications related to [diabetic retinopathy], such as tractional retinal detachment or neovascular glaucoma, and we can expect a new wave of patients with blindness and low vision.”

More Retina: Visit the Retina Resource Center