medwireNews: People with hypertension and prediabetes have significantly lower capillary density in the foveal (CDF) retinal region, indicating microvascular damage, than those with hypertension but normal glucose metabolism, say researchers.
Markus Schlaich (University of Western Australia, Perth) and team also found that “measures of glycemia were linearly associated with microvascular damage.”
The investigators report in Diabetes Care that CDF, as measured by optical coherence tomography angiography, was 32.0% in 40 individuals with hypertension and prediabetes (mean glycated hemoglobin [HbA1c] 5.9%; 41 mmol/mol) who were treated at the Royal Perth Hospital between 2016 and 2019.
This was significantly lower than the CDF of 36.7% observed among 62 participants with hypertension and normal glucose metabolism (mean HbA1c 5.3%; 34 mmol/mol), and the difference between the two groups remained significant after adjustment for age, sex, 24-hour diastolic blood pressure, and estimated glomerular filtration rate.
In addition, Schlaich and team identified significant inverse correlations between CDF and HbA1c as well as between CDF and fasting plasma glucose, but no correlation between CDF and insulin resistance according to HOMA-IR.
This was despite the fact that, in patients with HbA1c below 6.5% (48 mmol/mol), higher insulin resistance (HOMA-IR ≥2.5) was associated with lower CDF.
Specifically, CDF was 33.7% among 40 participants with higher insulin resistance compared with 36.3% among 56 participants with lower insulin resistance (HOMA-IR <2.5), a significant difference.
The researchers also assessed capillary density in the parafoveal retinal area but found no significant difference in measurements with respect to HbA1c or HOMA-IR.
Discussing their findings, Schlaich and co-authors note that “the data are only valid for patients with a combination of prediabetes and hypertension.”
They stress: “We cannot conclude that the same relationship between glycemia and retinal capillary damage would exist in the absence of hypertension.”
The team concludes that the study supports “the concept that microvascular damage may already occur before the diagnosis of [type 2 diabetes].”
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