Variability in HbA1c tied to poorer outcomes in T2D

  • Critchley JA & al.
  • Diabetes Care
  • 3 Oct 2019

  • International Clinical Digest
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Takeaway

  • HbA1c variability is strongly associated with overall mortality and emergency hospitalization and not explained by average HbA1c or hypoglycemic episodes.
  • Targets should focus on both stability and absolute HbA1c level.

Why this matters

  • Current guidelines promote both lower and stable HbA1c levels but tend to prioritize the former.

Study design

  • UK primary care data for 58,832 patients with type 2 diabetes (T2D), 2006-2009.
  • Funding: None.

Key results

  • After adjustments, both higher and very low average HbA1c (7.16%), increasing variability, and positive or negative HbA1c trajectories were all associated with higher all-cause mortality.
  • After adjustment for variability, average, and HbA1c trajectory, effect of average HbA1c seen only in the top 10% of HbA1c distribution (HR, 1.35; 95% CI, 1.24-1.47) for HbA1c >8.88% vs reference >6.09%-6.58%.
  • By contrast, graded mortality risk increase was seen with increasing variability, ranging from HR of 1.32 (95% CI, 1.21-1.44) in 25th-50th percentile for coefficient of variation, to HR of 1.93 (95% CI, 1.72-2.16) in top 10th percentile.
  • For coronary artery disease and ischemic stroke hospitalizations, risk increased for any HbA1c >7.16%. 
    • For the top 10% (>8.88%), the HR for hospitalization was 2.13 (95% CI, 1.91-2.37).

Limitations

  • Possible reverse causality, residual confounding.
  • Short duration.
  • Observational.