[Age and arterial hypertension in hemodialysis patients]

Hypertension is common in the elderly (here defined as people older than 60 years), affecting 60%-70% of this population. In this group, isolated systolic hypertension (ISH), defined as elevated systolic blood pressure (SBP) > or = 140 mm Hg and normal diastolic blood pressure (DBP) <90 mm Hg is the predominant subtype of hypertension.

The aim of this cross-sectional study was to investigate blood pressure differences according to age, especially the prevalence of ISH, in patients with end-stage renal disease (ESRD) undergoing regular maintenance hemodialysis, and to determine the importance of the interdialysis weight gain as a factor contributing to ISH.

Blood pressure was measured manually using mercury sphygmomanometer prior to and after dialysis procedure. Measurements were performed by educated staff members. Data on patient sex and age, duration of dialysis in total and weekly in hours, diabetic status, number of different antihypertensives used, and interdialysis weight gain were recorded. Patients were classified into four subgroups based on their systolic and diastolic blood pressure: normotensive (<140/<90 mm Hg); systolic-diastolic hypertension (SDH; > or = 140/> or = 90 mm Hg); ISH (> or = 140/<90 mm Hg); and isolated diastolic hypertension (IDH; <140/> or = 90 mm Hg). A total of 687 patients were included in final analysis and classified into 5 age groups: group 1, < or = 50; group 2, 50-59; group 3, 60-69; group 4, 70-79; and group 5, > or = 80. Student's t-test and ANOVA were used for continuous, normally distributed data, and chi2-test and Kruskal-Wallis test if otherwise. To identify the influence of IDWG on ISH, binary logistic regression was performed. The alpha <0.05 was considered statistically significant.

There were 376 male and 311 female patients, mean age 63.13. In the above age groups, a decrease in the prevalence of SDH by 29.8%, 28.4%, 19.8%, 19.5% and 8.3%. (chi2=12.438, df=4, p=0.014) and an increase in the prevalence of ISH by 25.4%, 25.2%, 39.0%, 35.9% and 50.0%, respectively, was recorded (chi2=15.670, df=4, p=0.003). There was no significant statistical difference in the prevalence of IDH. Using binary logistic regression, we tried to identify the predictors of ISH. ISH was treated as a dichotomous dependent variable. Independent variables were sex, age, diabetic status, percent of body weight reduction during the process of hemodialysis, antihypertensive therapy and duration of hemodialysis in months. Age, diabetic status, usage of antihypertensive medication and IDWG were identified as significant predictors of ISH. Compared to age group 1, groups 3, 4 and 5 were associated with a 1.875-fold (1.064-3.305; p=0.030), 1.981-fold (1.116-3.519; p=0.020) and 3.963-fold (1.667-9.421; p=0.002) increase in the risk of developing ISH. Diabetic status was associated with a 1.833-fold (1.106-3.039; p=0.019) and antihypertensive medication with 2.731-fold (1.477-5.051; p=0.001) risk increase. IDWG >3% was associated with a 1.543-fold (1.074-2.217 p=0.019) risk increase of ISH.

This study showed HTN to be still largely uncontrolled in patients undergoing hemodialysis. SBP remained constant in all age groups, even in the youngest, while a decrease in DBP was evident across age groups. A variety of factors contribute to this issue. Volume overload with other metabolic disorders that usually accompany chronic kidney disease (CKD) make these patients incline towards higher BP. Although IDWG in kilograms and percentage was significantly lower in older age groups, in logistic regression analysis IDWG larger than 3% was indicated as a positive predictor of ISH. When the same model was applied to SDH, IDWG >3% was not recognized as a statistically significant predictor of SDH (OR=1.225; 95%CI=0.819-1.832; p=0.323).

It is possible that dietary modification involving sodium restriction may provide more benefit for patients with ISH than for those with SDH. Nevertheless, dietary modifications need to be encouraged in all patients undergoing hemodialysis.