Blood pressure levels and outcomes in type 2 diabetes
Hypertension is common globally and is a major driver of cardiovascular and renal disease. Despite evidence of the benefits of blood pressure reduction in type 2 diabetes, the optimal blood pressure (BP) target remains uncertain and guidance varies.
The dose–response relationships between systolic and diastolic blood pressure (SBP and DBP) and major outcomes (including all‑cause mortality, cardiovascular events and renal outcomes) remain poorly defined, especially at lower BP levels.
To evaluate risk patterns across the full spectrum of BP, Wang and colleagues performed a systematic review of PubMed, Embase and Web of Science from inception to 30 November 2024, identifying cohort studies assessing associations between BP and a range of clinical outcomes. A one-stage, mixed-effects, dose–response meta-analysis – powered by a huge sample size, wide coverage of study populations and long follow-up duration – was conducted to assess the curvilinear associations.
A total of 89 cohorts, involving 5,875,364 adults with type 2 diabetes, were included in the meta-analysis. Mean follow-up was 6.3 years and the average age of participants was 60.5 years.
J-shaped associations were detected for SBP with all-cause mortality, and for SBP with cardiovascular events. A J-shaped association was also observed for DBP with all-cause mortality, with flattened risks at lower BP levels.
After excluding studies that included participants with baseline cardiovascular diseases or cancer, a significantly reduced risk of cardiovascular events was observed at lower SBP levels, as well as a flattened risk of all-cause mortality, suggesting potential reverse causation.
BP levels were linearly or monotonically associated with all renal outcomes, including eGFR decline and development of progression of albuminuria.
The lack of clear evidence from the study of a U-shaped association between BP and all-cause mortality suggests that previously reported harms of low SBP in people with type 2 diabetes are due to reverse causation and unmeasured confounding.
The authors caution that the insights into population-level risk associations offered by this study should not be used for treatment recommendations. The findings should be used to generate hypotheses for further studies to further elucidate the associations between BP and clinical outcomes, particularly at very low BP levels.
The full article can be read here.
