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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE  
Year : 2020  |  Volume : 31  |  Issue : 1  |  Page : 62-69
The relationship between body mass index and blood pressure in patients undergoing chronic hemodialysis: A reverse epidemiology in Jakarta, Indonesia


1 Division of Nephrology and Hypertension, Department of Internal Medicine, Faculty of Medicine, Universitas Indonesia – Cipto Mangunkusumo Hospital, Jakarta, Indonesia
2 Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia
3 Department of Community Occupational and Family Medicine, Faculty of Medicine, Universitas Indonesia – Cipto Mangunkusumo Hospital, Jakarta, Indonesia

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Date of Submission01-Sep-2018
Date of Decision04-Oct-2018
Date of Acceptance04-Oct-2018
Date of Web Publication3-Mar-2020
 

   Abstract 


In the general population, obesity is positively correlated with hypertension. On the other hand, there was hypothesis of “reverse epidemiology” in the relationship between body mass index (BMI) and blood pressure (BP) of hemodialysis (HD) patients. This study aimed to investigate the “reverse epidemiology” of the relationship between the two variables in Jakarta, Indonesia. Cross-sectional study was conducted at Cipto Mangunkusumo Hospital, Koja District Hospital, and Cengkareng District Hospital in July 2018. Total sampling was performed with a total of 525 HD patients aged >18 years. All data were analyzed from the medical records. Of 525 patients, 27.4% were obese. The post hoc analyses showed that obese patients had significantly lower post-HD systolic BP (P = 0.006) and diastolic BP (P = 0.004) than the normal-weight patients. The Chi-square analyses showed that the overweight group [odds ratio (OR) = 0.53; 95% confidence interval (CI) 0.31-0.87; P = 0.011] and the obese group (OR = 0. 63; 95% CI 0.400.97; P= 0.038) had significant protective effect (OR <1) on the post-HD hypertension. Being obese was a strong predictor for reduced BP (coefficient β = -0.02; P = 0.031). BMI is inversely associated with BP in patients undergoing chronic HD.

How to cite this article:
Abdullah Bawazir LA, Sianipar W, Buntaran S, Kekalih A. The relationship between body mass index and blood pressure in patients undergoing chronic hemodialysis: A reverse epidemiology in Jakarta, Indonesia. Saudi J Kidney Dis Transpl 2020;31:62-9

How to cite this URL:
Abdullah Bawazir LA, Sianipar W, Buntaran S, Kekalih A. The relationship between body mass index and blood pressure in patients undergoing chronic hemodialysis: A reverse epidemiology in Jakarta, Indonesia. Saudi J Kidney Dis Transpl [serial online] 2020 [cited 2020 Apr 7];31:62-9. Available from: http://www.sjkdt.org/text.asp?2020/31/1/62/279962



   Introduction Top


In the general population, obesity is associated with increased risk of mortality.[1] However, this theory could not be applied in chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients undergoing chronic hemodialysis (HD). It was suggested that increased body mass index (BMI) of CKD and ESRD patients was inversely associated with negative outcomes, which popularly called “the reverse epidemiology.”[2] A study in the general Korean population showed that BMI had a positive linear relationship with cardiovascular events.[3] However, this situation is different with patients undergoing chronic HD. A study by Agarwal[4] found that there was a higher prevalence of hypertension in HD patients with lean body mass. This study also suggested that obese patients had better control of blood pressure (BP) with the ability to isolate excess of fluid volume in extra-cellular space, but this explanation needs further study due to the missing link between lower BP in obese patients undergoing chronic HD and the prevalence of left ventricular hypertrophy.[4] The mechanism of how obese patients undergoing chronic HD had lower mortality rate remains unclear, even the cardiovascular events could not fully explain the “reverse epidemiology” between BMI and mortality.[4] The previous studies were conducted in patients undergoing chronic HD three times a week. In Indonesia, patients undergo chronic HD twice a week. This study aimed to determine the relationship between BMI and BP in patients undergoing chronic HD twice a week.


   Materials and Methods Top


Study design and setting This study used a cross-sectional design. The aim of the study was to determine the relationship between BMI and BP in ESRD patients undergoing chronic HD. It was hypothesized that BP was inversely correlated with BMI. The study was conducted in July 2018. Subjects in this study were the HD patients of Cipto Mangunkusumo Hospital, Koja District Hospital, and Cengkareng District Hospital. The protocol of this study was approved by the Health Research Ethics Committee, Faculty of Medicine, Universitas Indonesia - Cipto Mangunkusumo Hospital with reference number of the following: 0689/UN2.F1/ ETIK/2018.

Sampling method

A total sampling was conducted in this study. This study’s participants were ESRD patients aged >18 years who were undergoing chronic HD in three hospitals in Jakarta, which were Cipto Mangunkusumo Hospital, Koja District Hospital, and Cengkareng District Hospital.

Procedures and research instruments

This study obtained data from the medical records of patients. Medical records of all subjects were assessed to obtain background characteristics, pre-HD BP, post-HD BP, and BMI. The BP of all patients was measured in the supine position. The ultrafiltration was adjusted according to the increase of the weight from the previous HD session. The target of the ultrafiltration was to be as close as the dry weight of every patient. The identities of the patients remained confidential. As the study used medical records (secondary data), informed consent was not obtained.

Covariates and outcomes

Characteristics of the patients consisted of categorical data such as age (18-30 years, 3140 years, 41-50 years, 51-60 years, and >60 years), sex (men and women), employment (employed and unemployed), religion (Islam, Christian, Buddhism, and Hinduism), dialyzer membrane (single-use and reuse), vascular access (arteriovenous fistula, femoral, tunnel, and double-lumen catheter), categories of systolic and diastolic BP (DBP) in pre-HD and post-HD based on JNC 7 criteria (normal BP, pre-hypertension, stage I hypertension, and stage II hypertension), and categories of BMI based on Asia-Pacific criteria (underweight, normal weight, overweight, and obese). The BMI variable was the independent variable. The weight component in the BMI was the post-HD weight (measured after the HD procedure session was over). BP was the outcome of this study. The pre-HD BP had been measured before HD procedure session began. The post-HD BP was measured after HD procedure session had ended. To see the prevalence of hypertension according to BMI, BP was categorized into no hypertension [systolic BP (SBP) <140 mm Hg] and hypertension (SBP >140 mm Hg).


   Statistical Analysis Top


The categorical data are presented as frequencies (n) and percentages (%). The numerical data are presented as means and standard deviations (SDs). The P <0.05 used as statistical significance. The Chi-square test was performed to see the relationship between BMI and prevalence of hypertension. The distribution of mean SBP and DBP differences in pre-HD and post-HD according to patients’ BMI category was also analyzed with the Kruskal-Wallis and ANOVA test. The multi- variate analysis (linear regression model) was also performed to determine potential confounding factors in the relationship between BMI and BP. The software used for the statistical analysis of this study was IBM SPSS statistics version 20.0 (IBM Corp., Armonk, NY, USA).


   Results Top


[Table 1] presents the summary of patients’ characteristics. The majority of patients in this study were the patients of Cengkareng District Hospital (38.4%). The mean age of all patients was 49.5 years (SD 12.2). The age group of 51 -60 years dominated with a percentage of 29.9%. Majority of the patients were men (58.2%). More than half of the patients were unemployed (65.3%). Islam was the most practiced religion among the patients (88.1%). Majority of the patients were undergoing HD with reuse dialyzer membrane (69.9%). Of all patients, 68.5% used arteriovenous fistula as vascular access. The mean duration since initial HD was 3.1 years (SD 3.4).

In the BP aspect, the mean SBP in pre-HD and post-HD was 147.6 mm Hg (SD 24.7) and 142.9 mm Hg (SD 28.3), respectively. The mean DBP in pre- and post-HD was 81.3 mm Hg (SD 14.3) and 80.9 mm Hg (SD 15.0), respectively. Based on JNC 7 criteria, patients had SBP category of stage II hypertension in pre-HD and post-HD was 34.2% and 31.9%, respectively. The majority of patients had DBP category of normal BP in pre- and post-HD (53.7% and 53.9%, respectively). Of all patients, 38.2% had BMI of normal weight.
Table 1: Characteristics of the patients

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[Table 2] provides the mean differences among the groups of BMI. The significant mean differences were found at the post-HD mean SBP (P = 0.049) and DBP (P = 0.020). In post-HD, the mean SBP and DBP of obese category was the lowest (138.6 mm Hg and 78.4 mm Hg, respectively). In the post hoc analysis of post-HD BP, normal weight category was used as the reference category. There was a significant difference between normal- weight group and obese group in the mean SBP (P = 0.006) and the mean DBP (P = 0.004).
Table 2: Mean blood pressure according to body mass index.

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[Table 3] provides the summary of prevalence of hypertension according to BMI. There was a significant relationship between BMI and post-HD hypertension (P = 0.049). Using the normal weight as reference, the Chi-square test analysis showed that significant associations with post-HD hypertension were found in the overweight group [odds ratio (OR) = 0.53; 95% confidence interval (CI) 0.31-0.87; P = 0.011] and the obese group (OR = 0.63; 95% CI 0.40-0.97; P = 0.038).
Table 3: Prevalence of hypertension according to body mass index.

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[Table 4] provides the linear regression model of the relationship between HD patients’ characteristics and post-HD SBP. Being men and obese were the significant predictors for HD patients’ post-HD SBP (P = 0.008 and P = 0.031, respectively).
Table 4: Linear regression model of the relationship between hemodialysis patients' characteristics and post-hemodialysis systolic blood pressure.

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   Discussion Top


HD patients do not have similar clinical features with the general population. In the general population, BMI and BP are positively correlated, meanwhile, in the HD patients; the two variables are inversely related.[4] Determining this relationship in the HD patients is important to maximize the usage of HD to decrease the morbidity and mortality of HD patients.

The mean age of this study (49.5 years) was relatively lower than the mean age of CKD patients in a study by Chang et al[5] (62.9 years). This study also showed that the cumulative percentage of patients with an age group before 40 (18-30 years and 31-40 years) was 22.6%. This result warns that CKD in Jakarta could possibly affect more young adults before the age of 40 in the near future.

In this study, the HD patients’ means of pre- and post-HD SBP (147.6 mm Hg and 142.9 mm Hg, respectively) were higher than a study by Losito et al[6] (137.1 mm Hg and 131.0 mm Hg). This study showed that stage II hypertension dominated the BP group in pre- and post-HD. It is common that BP control in low- income countries is worse than high-income countries.[7] Besides, the pre-HD BP in this study was higher than the post-HD BP due to intradialytic changes in plasma volume according to a study by Ibrahim and Taweel.[8] The mean BMI of this study was 22.9 kg/m2 and was lower than the BMI of HD patients in a study by Abbott et al.[9] Of all patients, 27.4% were obese. The negative correlation between BMI and BP was supported by Agarwal.[4] This negative correlation between BMI and Bp was also supported by Salahudeen et al which showed that there was a significant negative correlation between the two variables, although the correlation coefficient (r) was also as weak as this study’s result.[10] This negative correlation was the result of lower BP and the prevalence of hypertension in the overweight and obese group compared to the normal- weight group. With this negative correlation, this study’s result could give an insight that the relationship between BMI and BP in HD patients was different in the general population. Obese HD patients tend to have more effective way to control BP through isolating fluid excess in extracellular space than lean HD patients.[4] Increased BMI is also followed by the increase of muscle which leads to increase of renalase, an enzyme which reduce BP by decreasing the level of catecholamine.[11] On the other hand, HD patients with lower BMI tend to have protein-energy wasting (loss of body protein) and inflammation.[12] The inflammatory cytokines, such as interleukin-6 and tumor necrosis factor-α, were related to the loss of appetite and the damage of endo- thelial cells which could increase the risk of cardiovascular and cerebrovascular death.[13] In HD patients with overweight or obese, adipose tissue plays a significant role in reducing the biological effect of tumor necrosis factor-α by creating tumor necrosis factor-α receptors.[14]

Thus, the adipose tissue is protective for cardiovascular event in HD patients.[12],[13],[14] The distribution of prevalence of hypertension in each group of BMI showed that the prevalence of hypertension was lower in the overweight and obese, compared to the prevalence of hypertension in the normal weight group. This distribution confirmed that low BMI had the tendency to have a high BP. In this study, patients with obesity had the lowest mean post-HD SBP and DBP. In the post hoc analyses, compared to normal weight, over-weight and obese had OR <1, which means that the two BMI groups were the protective factors to have hypertension in HD patients. These results were supported by Losito et al[15] which showed that patients with postdialysis hypertension had low BMI.

In the multivariate analysis using the linear regression model, being obese was still a strong predictor for post-HD SBP and the minus sign of the coefficient showed that it reduced SBP of HD patients (coefficient β = -0.02; P = 0.031). Being men was also a strong predictor for increased SBP. This was supported by a popular theory which stated that men account for a higher proportion of hypertension than women.[16] Duration since initial HD was also significantly associated with reduced BP. In this study, the mean duration since initial HD was 3.1 years. This result could help to explain the high mortality of 1st year HD, as studies showed that the mortality of 1st year HD was at its highest rate and would decrease in the following years.[17],[18]

There are limitations of this study. Pre-HD weight data were not complete in all HD patients and not included in the analyses, which could explain why the BMI did not significantly relate to pre-HD BP. Intermediate variables to explain the inverse relationship between BMI and BP, which is fluid excess, could not be analyzed as the pre-HD weight data were not complete. This study was also the first study to analyze the reverse epidemiology between BMI and BP in HD patients undergoing the procedure twice a week.


   Limitation of the Study Top


Based on a study by Sarafidis et al, it was recommended to diagnose hypertension based on Home Blood Pressure Monitoring (HBPM) and Ambulatory Blood Pressure Monitoring (ABPM).[19] In this study, we categorized hypertension grades based on pre-HD and post-HD BP. However, we could not perform HBPM and ABPM in this study due to limited resources and financial support. All HD patients were financially supported by the limited funds of Indonesia’s National Health Insurance. Patients in our dialysis centers usually agree with the office BP measurement as they also usually report to us that they perform BP measurement by themselves (using digital sphygmomanometer), or measured by local primary health-care physicians, or measured by local midwives or nurses because they are eager to know their own true BP outside of the clinic.


   Conclusion Top


BMI is inversely associated with BP in patients undergoing chronic HD. Further studies are needed to confirm the cause-effect relationship of BP, BMI, and mortality of HD patients.

Acknowledgment

The author appreciates the assistance from the staff of the HD Unit at Cipto-Mangunkusumo Hospital, Koja District Hospital, and Cengkareng District Hospital during the study.

Conflict of interest: None declared.



 
   References Top

1.
Prospective Studies Collaboration, Whitlock G, Lewington S, Sherliker P, Clarke R, Emberson J, et al. Body-mass index and cause- specific mortality in 900 000 adults: Collaborative analyses of 57 prospective studies. Lancet 2009;373:1083-96.  Back to cited text no. 1
    
2.
Agarwal R, Bills JE, Light RP. Diagnosing obesity by body mass index in chronic kidney disease: An explanation for the “obesity paradox?”Hypertension 2010;56:893-900.  Back to cited text no. 2
    
3.
Kong KA, Park J, Hong SH, Hong YS, Sung YA, Lee H. Associations between body mass index and mortality or cardiovascular events in a general Korean population. PLoS One 2017;12:e0185024.  Back to cited text no. 3
    
4.
Agarwal R. Body mass index-mortality paradox in hemodialysis: Can it be explained by blood pressure? Hypertension 2011;58:1014-20.  Back to cited text no. 4
    
5.
Chang TJ, Zheng CM, Wu MY, et al. Relationship between body mass index and renal function deterioration among the Taiwanese chronic kidney disease population. Sci Rep 2018;8:6908.  Back to cited text no. 5
    
6.
Losito A, Del Vecchio L, Lusenti Tet al. Systolic blood pressure and mortality in chronic hemodialysis patients: Results of a nationwide Italian study. J Clin Hypertens (Greenwich) 2013;15:328-32.  Back to cited text no. 6
    
7.
World Health Organization. Global Status Report on Noncommunicable Diseases. Geneva: World Health Organization; 2014.  Back to cited text no. 7
    
8.
Ibrahim S, Taweel A. Influence of plasma volume status on blood pressure in patients on maintenance hemodialysis. Dial Transplant 2007;36:13-24.  Back to cited text no. 8
    
9.
Abbott KC, Glanton CW, Trespalacios FC, et al. Body mass index, dialysis modality, and survival: Analysis of the United States renal data system dialysis morbidity and mortality wave II study. Kidney Int 2004;65:597-605.  Back to cited text no. 9
    
10.
Salahudeen AK, Fleischmann EH, Bower JD, Hall JE. Underweight rather than overweight is associated with higher prevalence of hypertension: BP vs BMI in haemodialysis population. Nephrol Dial Transplant 2004;19:427- 32.  Back to cited text no. 10
    
11.
Desir GV. Regulation of blood pressure and cardiovascular function by renalase. Kidney Int 2009;76:366-70.  Back to cited text no. 11
    
12.
Kalantar-Zadeh K, Rhee CM, Chou J, et al. The obesity paradox in kidney disease: How to reconcile it with obesity management. Kidney Int Rep 2017;2:271-81.  Back to cited text no. 12
    
13.
Park J, Ahmadi SF, Streja E, et al. Obesity paradox in end-stage kidney disease patients. Prog Cardiovasc Dis 2014;56:415-25.  Back to cited text no. 13
    
14.
Kalantar-Zadeh K, Kopple JD. Obesity paradox in patients on maintenance dialysis. Contrib Nephrol 2006;151:57-69.  Back to cited text no. 14
    
15.
Losito A, Del Vecchio L, Del Rosso G, Locatelli F. Postdialysis hypertension: Associated factors, patient profiles, and cardiovascular mortality. Am J Hypertens 2016;29:684-9.  Back to cited text no. 15
    
16.
World Health Organization. A Global Brief on Hypertension. Geneva: World Health Organization; 2013.  Back to cited text no. 16
    
17.
Wingard RL, Chan KE, Lazarus JM, Hakim RM. The “right” of passage: Surviving the first year of dialysis. Clin J Am Soc Nephrol 2009;4 Suppl 1:S114-20.  Back to cited text no. 17
    
18.
Robinson BM, Zhang J, Morgenstern H, et al. Worldwide, mortality risk is high soon after initiation of hemodialysis. Kidney Int 2014;85: 158-65.  Back to cited text no. 18
    
19.
Sarafidis PA, Persu A, Agarwal R, et al. Hypertension in dialysis patients: a consensus document by the European Renal and Cardiovascular Medicine (EURECA-m) working group of the European Renal Association - European Dialysis and Transplant Association (ERA-EDTA) and the Hypertension and the Kidney working group of the European Society of Hypertension (ESH). J Hypertens 2017;35:657-76.  Back to cited text no. 19
    

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Correspondence Address:
Lucky Aziza Abdullah Bawazir
Division of Nephrology and Hypertension, Department of Internal Medicine, Faculty of Medicine, Universitas Indonesia – Cipto Mangunkusumo Hospital, Jakarta 10350
Indonesia
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DOI: 10.4103/1319-2442.279962

PMID: 32129198

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