Uncontrolled blood pressure may trigger diabetic retinopathy

Untreated and poorly controlled hypertension increases the risk of any diabetic retinopathy (DR) in Asians with diabetes and hypertension, according to a recent Singapore study.

“To the best of our knowledge, our study is the first to examine the association of hypertension treatment with DR using population-based samples,” said researchers. “Strengths of this study include the use of large, population-based, multi-ethnic sample of diabetic participants with hypertension.”

The study included 2,189 hypertensive adults (aged 40–80 years; 50.4 percent male) of Chinese, Malay and Indian ethnicity in Singapore. Any and vision-threatening (VT) DR was reported in 33.8 percent (n=740) and 9.0 percent (n=197) of participants, occurring comparably across ethnic groups (p=0.2 and p=0.8, respectively). Only 12.8 percent (n=279) adults had controlled hypertension. [PLoS One 2020;15:e0229665]

Multivariate logistic regression analysis showed that, relative to those with treated and controlled hypertension, participants with treated but poorly controlled disease were at a significantly elevated risk of developing any DR (odds ratio [OR], 1.97, 95 percent confidence interval [CI], 1.39–2.83). The same was true for those with untreated hypertension (OR, 2.01, 95 percent CI, 1.34–3.05).

In contrast, those who had treated but moderately controlled hypertension did not suffer from such risks (OR, 0.97, 95 percent CI, 0.63–1.50).

A similar effect was reported for systolic blood pressure (SBP). Those in the top (OR, 2.60, 95 percent CI, 1.78–3.80) and third (OR, 1.89, 95 percent CI, 1.35–2.65) quartiles of SBP were significantly more likely to develop any DR. Each standard deviation (SD) increase in SBP corresponded to a 45-percent increase in any DR risk (p_trend<0.001).

Pulse pressure (PP) followed the same trend, but to a greater degree. The second (OR, 1.53, 95 percent CI, 1.07–2.18), third (OR, 2.91, 95 percent CI, 2.03–4.2) and top (OR, 3.43, 95 percent CI, 2.27–5.23) PP quartiles were all associated with a greater risk of any DR, with each SD increase leading to a 61-percent jump in DR likelihood (p_trend<0.001).

In terms of VTDR, high values of SBP (OR for each SD increase, 1.44, 95 percent CI, 1.19–1.76; p_trend<0.001) and PP (OR for each SD increase, 1.67, 95 percent CI, 1.37–2.06; p_trend<0.001) remained significant risk factors, while hypertension categories (untreated vs treated) did not.

“[I]n a multi-ethnic sample of Asian adults with diabetes and hypertension, both treated and poorly controlled and untreated hypertension were associated with any DR,” said researchers. “In subgroup analyses stratified by ethnicity, hypertension categories were significant in Malay and Indians but not in Chinese, but associations of SBP and PP with any DR were consistently present in all three ethnic groups.”

“Our findings suggest that in participants with both diabetes and hypertension, a tighter control of BP may help prevent DR,” they added.