Differences in the impact of newly diagnosed type 2 diabetes on cardiovascular mortality between normotensive and hypertensive individuals

Objective: We investigated the interrelationship between hyperglycemia and hypertension on cardiovascular mortality in the middle-aged and elderly people. Methods: In this retrospective cohort study that used data from the Hiroshima Study on Glucose Metabolism and Cardiovascular Diseases, we included 16,564 participants without cardiovascular disease (mean age: 65.8 years; 6179 normoglycemic people, 3017 people with newly diagnosed type 2 diabetes, and 7368 people with prediabetes per the 75-g oral glucose tolerance test). Hypertension was defined as the use of antihypertensive medications and/or having a systolic/diastolic blood pressure of at least 140/90 mm Hg. Results: During a median follow-up period of 12.4 years, a total of 1513 cardiovascular death occurred. Cardiovascular death rates per 1000 participant-years were 4.01, 4.98, 8.33, 8.22, 8.81, and 11.1 among normotensive participants with normal glycemia, prediabetes, and diabetes and hypertensive participants with normal glycemia, prediabetes, and diabetes, respectively. Prediabetes was significantly associated with a high risk of cardiovascular mortality in normotensive individuals [hazard ratio: 1.24, 95% confidence interval (95% CI): 1.02-1.50] but not in hypertensive individuals. Type 2 diabetes was associated with a high risk of cardiovascular mortality in both normotensive (hazard ratio: 1.94, 95% CI: 1.55-2.43) and hypertensive individuals (hazard ratio: 1.35, 95% CI: 1.13-1.62). Stratified analyses revealed no significant impact of type 2 diabetes on cardiovascular mortality in hypertensive individuals aged at least 65 years. Conclusion: The effect of hyperglycemia on cardiovascular death differed with age and the presence or absence of hypertension, demonstrating the clinical importance of case-specific risk assessments.