SG data affirm link between elevated BP and CVD mortality among individuals with T2D

Individuals with type 2 diabetes (T2D) who have high blood pressure (BP) levels are at increased risk of death from cardiovascular disease (CVD), according to a large registry cohort in Singapore. However, the risk increase is also present for those who have low diastolic BP.

Over a 7-year follow-up, 4,085 of the 83,721 patients with T2D (mean age 65.3 years, 50.6 percent women, 78.9 percent on antihypertensive medications) died from CVD. This corresponded to an incidence rate of 7.6 cases per 1,000 persons a year. [J Am Heart Assoc 2023;doi:10.1161/JAHA.123.030772]

Patients with systolic BP of 120–129 and 130–139 mm Hg had the lowest annual CVD mortality rate in the absence or presence of CVD comorbidity, respectively. In terms of diastolic BP, those with 80–89 mm Hg had the lowest annual rate, regardless of pre-existing CVD morbidity.

In multivariable Cox regression analysis, systolic BP showed a graded relationship with a significant increase in CVD mortality. The risk of CVD death was consistently elevated at ≥130 mm Hg vs 120–129 mm Hg for patients without pre-existing CVD (130–139 mm Hg: hazard ratio [HR], 1.16, percent confidence interval [CI], 1.01–1.33; ≥140 mm Hg: HR, 1.87, 95 percent CI, 1.65–2.12) and those with CVD (≥140 mm Hg: HR, 1.27, 95 percent CI, 1.12–1.45).

Similar patterns were observed in subgroups of young (<65 years; ≥140 mm Hg: HR, 1.87, 95 percent CI, 1.55–2.25) and older patients (≥65 years: ≥140 mm Hg: HR, 1.49, 95 percent CI, 1.35–1.64).

On the other hand, the risk-increase in CVD mortality associated with elevated diastolic BP was seen only among patients without pre-existing CVD (≥90 vs 70–79 mm Hg: HR, 1.32, 95 percent CI, 1.05–1.67) and older patients (≥90 vs 70–79 mm Hg: HR, 1.55, 95 percent CI, 1.24–1.95). Notably, diastolic BP levels below 70 mm Hg were paradoxically associated with increased CVD mortality risk across all subgroups of patients with T2D. 

Sensitivity analysis restricted to patients receiving antihypertensive medications yielded consistent results.

Lower BP targets supported

“Our findings of the association of higher achieved BP levels with CVD mortality are consistent with many previous studies and randomized controlled trials … [as well as extend] the knowledge of the relationship of BP with CVD in patients with diabetes,” the investigators said.

They added that their data support the guideline recommendation to lower BP targets to <130/80 mm Hg for T2D patients of Asian origin.

“Targeting diastolic BP levels <90 mm Hg might be sufficient. [However], patients who achieve diastolic BP levels <70 mm Hg require careful evaluation of incurrent illness and comorbidities, BP trends, and medications. The shared decision making on diastolic BP levels must also account for systolic BP levels, which are a stronger predictor of CVD mortality than diastolic BP,” the investigators pointed out.

Concerns have been raised regarding excessive diastolic BP lowering being a risk factor for myocardial ischaemia in patients with pre-existing coronary artery disease. Large arteries undergo thickening with age, and diastolic BP tends to decrease, as the investigators explained. This thickening process occurs more rapidly in people with diabetes, resulting in lower diastolic BP and a higher risk of vascular disease.

“Thus, low diastolic BP might be related to worst health outcomes in the general population, high‐risk patients, and those with diabetes… However, how much of the elevated CVD risk is from low diastolic BP versus thickened arteries per se remains to be established,” they said.