Introduction:
Since dialysis adversely affects the quality of life and is related to high rates of cardiovascular events and mortality, avoiding the need for dialysis is clinically relevant. Although both hyperglycemia and hypertension are highly predictive of kidney disease [1], only a few studies have investigated the associations between the severity of hypertension and risk of end-stage renal disease (ESRD) especially the initiation of renal replacement therapy in the presence or absence of diabetes mellitus (DM) in the same cohort at the same time and under the same conditions.
More strict blood pressure targets were recently recommended in the guidelines for hypertension by the American College of Cardiology (ACC) and the American Heart Association (AHA) [2]. In these guidelines, the definition of adult hypertension was reduced from the long-standing threshold of 140/90 mm Hg to 130/80 mm Hg. Although DM and hypertension defined as SBP ≥140 mmHg, DBP ≥90 mmHg or the use of antihypertensive treatment are well-known risk factors for ESRD defined according to the initiation of renal replacement therapy [3], various SBP levels have not been investigated with regard to the prevention of dialysis according to DM status. Such an investigation would have clinical relevance. The risk of chronic kidney disease (CKD) defined as the requirement for dialysis, transplantation or by the notation of kidney disease on the death certificate and confirmed by medical record review significantly increased from SBP ≥160 mmHg compared to SBP <120 mmHg with adjustment for DM [4]. Also, the risk of ESRD defined as receipt of renal transplant or maintenance dialysis increased in accordance with increases in SBP with adjustment for DM [5]. Although Hsu et al. [5] investigated the impacts of the presence of DM and stratified SBP on ESRD defined as described above, HbA1c was not used in defining DM. Moreover, only age was adjusted for as a covariate. Tozawa et al. [6] showed that elevated SBP was a risk factor for the development of ESRD among Japanese with and without DM. Also, Iseki et al. [7] showed that hyperglycemia defined as fasting blood glucose ≥126 mmHg was a significant risk factor for the development of ESRD in a Japanese general population. However, these studies [6.7] did not use HbA1c to define DM and also did not evaluate the impact of combinations of various SBP cut-offs among people with and without DM on starting dialysis. Thus, the impacts of blood pressure control and cut-off values on renal replacement therapy among people with and without DM are still unknown.
Moreover, although patients with renal disease or on dialysis tend to be prescribed hypertensive medication more often than those without renal disease or on dialysis [1.4.8], these studies [4.5] did not adjust for antihypertensive agents as a covariate. Thus, the effects of antihypertensive medication must be considered in evaluating the impact of various SBP levels on the initiation of dialysis.
Therefore, we investigated the risk of various SBP values for the initiation of dialysis in the presence or absence of DM in addition to considering the risk of various levels of SBP with adjustments for the use of antihypertensive medications.