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Diabetes duration, HbA1c associated with cause-specific mortality in Mexican adults
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Among Mexican adults, the rate of death from diabetes-related complications rose steeply with longer disease duration, with death rates from vascular, renal and infectious causes 12 times higher for those with diagnosed diabetes for at least 10 years vs. those without the disease, according to findings published in The Lancet Diabetes & Endocrinology.
“Evidence of the effect of diabetes on mortality has been derived largely from high-income countries, where patients might receive early diagnosis, have good access to medical care and can achieve good glycemic control,” William G. Herrington, MD, MBBS, MRCP, a senior clinical research fellow with the MRC Population Health Research Unit, Clinical Trial Service Unit and Epidemiological Studies Unit of the University of Oxford, and colleagues wrote. “In such populations, diabetes almost always doubles the all-cause mortality rate, with most deaths due to increases in vascular disease, infection and some cancers, and each 5 years’ longer duration of diabetes is associated with about a 20% further increase in vascular risk.”
In an analysis of the Mexico City Prospective Study, researchers observed that more than 1 in 5 adults had been diagnosed with diabetes by age 60 years, and glycemic control was poor, with mean HbA1c at 10%. In the study, previously diagnosed diabetes was associated with a quadrupling of the all-cause mortality rate during the subsequent 12 years, researchers wrote, with main excess mortality from renal and vascular disease, infection and acute diabetes crises.
In a long-term follow-up analysis of the Mexico City Prospective Study, Herrington and colleagues analyzed data from 133,662 adults aged 35 to 74 years recruited from two districts of Mexico City between April 1998 and September 2004, who provided nonfasting blood samples. Participants with any chronic disease aside from diabetes were excluded. Researchers tracked deaths in the cohort through January 2016 via linkage to the death registry and used Cox regression analyses to estimate the separate relevance of previously diagnosed and undiagnosed diabetes at recruitment with mortality, with age as the underlying time variable. Researchers also estimated the association of HbA1c with mortality in participants without diabetes at recruitment.
Within the cohort, 16,940 had previously diagnosed diabetes (mean HbA1c, 8.9%), 6,541 had undiagnosed diabetes (mean HbA1c, 7.7%), and 110,181 had no diabetes at recruitment (mean HbA1c, 5.4%). During a mean follow-up of 13.9 years, 7,683 participants died, including 4,401 from vascular, renal or infectious diseases and 318 from acute diabetes crises.
Compared with participants without diabetes at recruitment, the death rate ratio was 3 (95% CI, 2.7-3.4) for those with undiagnosed diabetes and rose with diabetes duration among those with diagnosed diabetes. The death rate ratio was 4.5 (95% CI, 4-5) for those with diabetes duration of 5 years or less (n = 5,042), 6.6 (95% CI, 6.1-7.1) for those with disease duration of 5 to 10 years (n = 7,713), and 11.7 (95% CI, 10.7-12.7) for those with disease duration of at least 10 years (n = 4,185).
Risk ratios also rose with HbA1c measurements, according to researchers. The death rate ratio was 5.2 (95% CI, 8.5-8.7) for those with HbA1c 9% or less, 6.8 (95% CI, 6.2-7.4) for those with HbA1c between 9% and 11% and 10.5 (95% CI, 9.7-11.5) for those with HbA1c at least 11%.
The researchers also noted that diabetes was particularly strongly associated with death from renal disease. For those with previously diagnosed diabetes with disease duration of 5 to 10 years or baseline HbA1c between 9% and 11%, the death risk ratio for renal disease was 24.2 (95% CI, 20.5-28.6) and 22.6 (95% CI, 18.8-27.2), respectively, vs. those without diabetes.
“This finding is consistent with observations from diabetes populations from high-income countries, in which microvascular complications were more steeply associated with duration of diabetes than were macrovascular complications,” the researchers wrote. “However, our estimate of the rate at which the RR for renal death increased with longer duration of diabetes was somewhat larger than that seen in earlier studies, perhaps reflecting the worse glycemic control or low use of renin-angiotensin system blockade, or both.”
Diabetes was not strongly associated with the combination of deaths from other causes apart from acute glycemic crises. Researchers found that HbA1c was not positively associated with mortality in participants without diabetes at recruitment.
“In populations in which obesity and diabetes are overwhelming health services, the onset of diabetes needs to be delayed — and its treatment improved — to substantially reduce premature adult mortality,” the researchers wrote. – by Regina Schaffer
Disclosures: Harrington reports he has received grants from Boehringer Ingelheim. Please see the study for the other authors’ relevant financial disclosures.
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