HbA1c variability strongly associated with CVD and mortality in T2DM
A prospective 10-year cohort study of 147,811 Hong Kong patients with type 2 diabetes mellitus (T2DM) finds a strong association between HbA1c variability and the incidence of cardiovascular disease (CVD) as well as mortality across all age groups.
At a median follow-up of 7.4 years (1.02 million person-years), the overall number of events was 40,785, including 27,793 CVD events and 23,175 all-cause mortalities. The CVD incidence was 23.5/1,000 person-years (PY) vs 33.6 events/1,000 PY among patients with the lowest HbA1c variability (0–0.24 percent) vs patients with the highest HbA1c variability (≥3.0 percent). The all-cause mortality rate was 17.9 events/1,000 PY vs 33.2 events/1,000 PY in the highest vs the lowest HbA1c variability groups, while the composite incidence of CVD and all-cause mortality was 35.1 events/1,000 PY vs 52.4 events/1,000 PY. [Diabetes Obes Metab 2020, doi:10.1111/dom.14034]
“A total of 14 studies have examined the relationship between HbA1c variability and the risk of CVD and mortality among patients with T2DM … [but] most were limited by either a small sample size, low number of incident outcomes, short follow-up period, or lack of adjustments for potential confounders such as duration of diabetes, comorbidities, and baseline medications,” wrote the researchers. [Diabetes Care 2015;38:2354-2369] “This large study is the first to investigate the age-specific associations between HbA1c variability and risk CVD and mortality among Chinese patients with diabetes.”
“Positive and log-linear associations between HbA1c variability and the risk of CVD, all-cause mortality, and composite outcomes were found across all age groups,” observed the researchers.
A 28 percent greater risk of the composite outcome of CVD and all-cause mortality was observed per every 1 percent increase in HbA1c variability in the 45–54 years of age group (hazard ratio [HR], 1.28; 95 percent confidence interval [CI], 1.21 to 1.35). The same increase in HbA1c variability in the 75–84 years of age group was associated with only 14 percent greater risk of composite outcome (HR, 1.14; 95 percent CI, 1.11 to 1.17). “A comparable effect [of HbA1c variability on the composite outcome of CVD incidence and all-cause mortality] was observed when stratifying subjects by gender, smoking status, BMI, baseline systolic blood pressure, LDL-C levels, eGFR, and Charlson’s comorbidity index,” reported the researchers.
The HRs for risk of CVD and all-cause mortality were higher among patients with usual HbA1c level of <7.9 percent compared with patients whose usual HbA1c level was ≥8 percent (composite outcome HR for 7–7.9 percent group, 1.35; 95 percent CI, 1.27 to 1.42), with the highest risk observed among those whose usual HbA1c level was <7 percent (composite outcome HR, 1.83; 95 percent CI, 1.66 to 2.03). “The risk [of CVD and all-cause mortality] among patients with usual HbA1c of <7 percent vs those with usual HbA1c level of ≥8 percent was about 8 times greater,” reported the researchers.
“The HbA1c variability may provide additional valuable information as a potential predictor for the development of CVD and all-cause mortality among patients with diabetes. Clinicians should monitor HbA1c fluctuations in addition to the absolute HbA1c value,” concluded the researchers.