Nighttime blood pressure is elevated in diabetes patients as well as those with chronic kidney disease (CKD), previous research suggests. Now a new Japanese study finds that systolic blood pressure (SBP) is higher at night in elderly patients with both prediabetes and CKD.
The findings indicate a relationship between diabetic status, kidney function, and nighttime blood pressure. “Previous studies suggested that sympathetic overactivity is present in both prediabetes and CKD,” Kenji Obayashi, MD, of Nara Medical University, in Nara, Japan, and colleagues wrote in the Clinical Journal of the American Society of Nephrology. “In addition, asymmetric dimethylarginine, a major endogenous competitive inhibitor of nitric oxide synthase, is elevated in individuals with diabetes mellitus as well as in patients with CKD.”
The investigators collected clinical and laboratory data from 1,227 Japanese men and women older than 60 participating in the Housing Environments and Health Investigation Among Japanese Older People in Nara, Kasai Region (HEIJO-KYO) study. For 2 days, participants wore an ambulatory blood pressure monitor and actigraph, kept a sleep diary, and abstained from alcohol.
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Results showed that average nighttime SBP was 115.7 mm Hg. On multivariable analysis, patients with both prediabetes and CKD had significantly elevated SBP by 2.9 mm Hg and those with diabetes and CKD by 7.8 mm Hg, compared with individuals with normal blood sugar levels and no CKD. No increases were observed in patients with prediabetes, diabetes, or CKD alone. Researchers adjusted for patient age, sex, smoking, and daytime SBP.
The magnitude of the difference in nighttime SBP is worrisome. A meta-analysis by José Boggia, MD, and colleagues published in the Lancet (2007;370:1219-1229) found a dose-dependent relationship between higher nighttime SBP and mortality. For example, a 3.5 mm Hg elevation in SBP was linked with a 5% increase in mortality from all causes.
Dr. Obayashi and colleagues considered the impact of sleep disordered breathing, such as sleep apnea, and could not rule out a residual effect.
