By Harold L. Karpman, MD, FACC, FACP
Clinical Professor of Medicine, UCLA School of Medicine
Dr. Karpman reports no financial relationships relevant to this field of study.
SYNOPSIS: An increase of 20 mmHg in systolic blood pressure was associated with a 58% higher risk of new-onset diabetes mellitus, whereas an increase of 10 mmHg in diastolic blood pressure was associated with a 52% higher risk of developing new-onset diabetes mellitus.
SOURCE: Emdin CA, et al. Usual blood pressure and risk of new-onset diabetes. Evidence from 4.1 million adults and a meta-analysis of prospective studies. J Am Coll Cardiol 2015:66;1552-1562.
Type 2 diabetes mellitus (T2DM) is associated with twice the risk of all-cause mortality and three times the risk of cardiovascular mortality relative to age and sex-matched controls.1 In 2011, 366 million people worldwide had T2DM and that number was expected to increase to 552 million by 2030.2 Although elevated blood pressure (BP) has been demonstrated to be an independent risk factor for fatal and nonfatal cardiovascular events in the past,3 it has not been clearly demonstrated that an elevated BP may contribute to new-onset T2DM. Emdin et al analyzed the records of more than 4 million individuals free from T2DM and cardiovascular disease in a contemporary U.K. primary care population and performed a meta-analysis of existing prospective studies in an attempt to accurately determine the association between climbing BP and T2DM.4
Researchers analyzed 4,694,120 medical records from the U.K. Clinical Practice Research Datalink. Patients were eligible for inclusion if they had a BP measurement performed between Jan. 1, 1990, and Jan. 1, 2013, and if they were between 30 and 90 years of age at the time of measurement. All patients with pre-existing vascular disease (i.e., ischemic heart disease, cerebrovascular disease, heart failure, peripheral vascular disease, or renal disease) and T2DM were excluded. To reduce measurement error to which single BP measurements are prone and to diminish the impact of short-term fluctuations in BP on observed associations, the initial measurement was considered to be the “usual blood pressure.” In the residual cohort of 4,132,138 individuals, 186,698 new-onset T2DM events were identified. After extensive analysis, the authors concluded that an increase of 20 mmHg in systolic BP was associated with a 58% higher risk of new-onset T2DM, whereas an increase of 10 mmHg diastolic BP was associated with a 52% higher risk of developing T2DM.
COMMENTARY
The data analyzed in this study were massive. However, the electronic health records utilized were routinely collected, and significant variations in BP determinations were certainly quite possible. The authors compared their results with their analysis of 30 prospective observational studies involving 285,664 participants who developed 17,388 T2DM associations. The meta-analysis revealed that for each 20 mmHg above usual systolic BP, there was a 77% higher risk of new-onset T2DM and the results were quite similar to the findings of the their study.4 Of course, large electronic medical records studies have many potential sources of errors, which may have contributed to the final results, but the authors vigorously attempted to prevent any errors from occurring in their careful analysis of the data.
The strengths of the associations between diastolic and systolic BP and the risk for T2DM declined with increasing body mass index and/or age. Because of the many potential data weaknesses in this enormous study, I agree with the authors that further investigation is needed to determine whether the associations observed in this study were causal in nature.
REFERENCES
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Kannel WB, et al. Diabetes and cardiovascular risk factors: The Framingham study. Circulation 1979;59:8-13.
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Whiting DR, et al. IDF diabetes atlas: Global estimates of the prevalence of diabetes for 2011 and 2030. Diabetes Res Clin Pract 2011;94:311-321.
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Lewington S, et al. Prospective studies collaboration. Age-specific relevance of usual blood pressure to vascular mortality: A meta-analysis of individual data for one million adults in 81 prospective studies. Lancet 2002;360:1903-1913.
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Emdin CA, et al. Usual blood pressure and risk of new-onset diabetes. Evidence from 4.1 million adults and a meta-analysis of prospective studies. J Am Coll Cardiol 2015:66;1552-1562.
