Effect of Age on Interdependence and Hierarchy of Cardiovascular Risk Factors in Hypertensive Patients
Is there an age-related interdependence between blood pressure (BP), other metabolic syndrome components, and high-sensitivity C-reactive protein (hs-CRP) in hypertensive subjects?
A total of 5,712 nondiabetic patients evaluated in outpatient hypertension clinics were included and divided into five age groups (ages 40-49, 50-59, 60-69, 70-79, and >80 years). BP, evaluated by both office and 24-hour ambulatory BP monitoring, and the metabolic and inflammation parameters were determined after a >2-week drug washout period. Insulin resistance was assessed with the Homeostasis Model of Assessment–Insulin Resistance index (HOMA-IR).
A total of 50.1% were men; age range 40-95 years. The prevalence of the metabolic syndrome remained stable across the age groups. There was a stable or increased association between waist circumference and HOMA-IR and fasting plasma glucose. However, the association between waist circumference and ambulatory BP monitoring systolic BP (r2 decreased from 9.9% to 1.0%, p < 0.001), high-density lipoprotein cholesterol (HDL-C; r2 decreased from 21% to 4.9%, p = 0.002), and triglyceride levels (r2 decreased from 17.5% to 1.9%, p < 0.001) decreased with age. Hs-CRP correlated with all metabolic syndrome components in all age groups (p < 0.001 for all). It became the strongest determinant of ambulatory BP monitoring systolic BP (p < 0.001) and HDL-C (p < 0.05) in patients >80 years old. In contrast, its association with waist circumference markedly decreased.
In conclusion, hypertension and dyslipidemia, but not fasting plasma glucose, dissociate from central obesity with advancing age. They are increasingly determined by low-grade inflammation, independently of central obesity. These changing associations might underlie the weakening of obesity as a cardiovascular risk factor in older persons.
The authors infer that hs-CRP is a determinate of systolic BP and low HDL-C. There is no evidence that it is more than an epiphenomenon. The long-term cardiovascular event rates in this cohort will provide interesting information.
Keywords: Metabolic Syndrome X, Obesity, Abdominal, Cholesterol, Waist Circumference, Dyslipidemias, Risk Factors, Blood Pressure, Homeostasis, Insulin Resistance, Hypertension, Glucose
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