Worldwide, over 200 million people are estimated to suffer from CKD that are susceptible to develop End-stage Renal Disease (ESRD) if no action is done to diagnose and treat them in early stages[18]. ESRD represents the tip of the iceberg and the actual number of patients with CKD is a lot more. Studying the prevalence of CKD in Palestine is important as it helps in early detection and thus prevention and control diabetic nephropathy.
To the best of our knowledge, this study was the first epidemiological investigation on CKD prevalence among Palestinian diabetic patients attending primary care consults. It showed that 23.6% (95%CI 19.1–28.4) of diabetic patients in the North West Bank have CKD. Sweileh et al reported a prevalence of 35.5% of CKD in Palestine in 2008[15]. However, this study was carried out among diabetic hypertensive patients and targeted hospitalized diabetic patients, which explain the difference in the prevalence rate. Additionally, it used only one creatinine reading which would have been probably representing acute rather than chronic kidney injury.
Results on the prevalence of CKD among diabetic patients are variable; like Finland (16.2%) [19], Southern Ethiopia (23.4%) [20] Spain (27.9%)[21]. Unfortunately, similar data from the surrounding countries is lacking. This variation on the prevalence of CKD among Diabetic patients is attributed to difference in the definitions adopted and the characteristics of the studied populations.
Studying the risk factors associated with CKD, especially the modifiable factors, is important to develop prevention and control interventions. The prevalence rate of HTN reported in this study among patients with type 2 diabetes (75%) was high. It is more than what have been reported in the neighboring countries; Jordan (72.4%)[22], Qatar (64.5%)[23] and Saudi Arabia (53%)[24]. This relatively higher rate of HTN could be related to the fact that most diabetic patients included in the study were obese and aged > 60 years.
This study showed a significant relation (P Value < 0.001) between BP and the kidney damage, reflected by decreased eGFR as systolic BP increases (Table 2). Diabetic patients with HTN are 4.4 more times prone to develop CKD compared to diabetic patients with normal BP. These findings are consistent with literature from different countries [14, 19, 21]. This risk of CKD and kidney damage can be further increased as the age increases. There is a great overlap between HTN and impaired renal function. The patient goes into a vicious cycle where decreased kidney function causes an elevation in BP and this elevation will cause further kidney damage and subsequent decrease in the kidney function.
The high prevalence of HTN among our patients is alarming and should be taken into consideration, as many studies reported the relation between high BP and development of ESRD. A study in Japan showed that patients with high BP have 15 times more chances of developing ESRD in comparison to patients with controlled BP (= 110/70) [25]. This is important and more attention should be focused toward a better BP control among diabetic patients.
In this study, 30.4% of the patients were smokers; higher proportion of them among the CKD group (39.6%). Smoking did correlate with renal function progression in this study (P value = 0.022). The association between smoking and presence of CKD among diabetic patients is clearer, with most of the studies showing a significant relationship between these two variables. Recently two meta-analysis suggested evidence for cigarette smoking as an independent risk factor for CKD[13, 26]. Xia et al reported that compared with never-smokers, the rsik of incident CKD were 1.27 (95% CI 1.19–1.35) for ever-smokers, 1.34 (95% CI 1.23–1.47) for current smokers and 1.15 (95% CI 1.08–1.23) for former smokers [13]. The not well understood nephrotoxic effect of smoking that includes endothelial cell dysfunction and the increased insulin resisitance regardless of the diabetic status can explain this finding[13].
Regarding age, it was found to be a significant risk factor (P value < 0.001). This can be explained by the steady decline in GFR with normal aging; a process that is accelerated by superimposing factors like diabetes. Many studies reported age as a risk factor for CKD among diabetic patients [11, 14, 19, 20]. Additionally, as noted in Table 2, a significant decrease in eGFR was reported as the age increases. These results indicate the need for robust screening of diabetic patients with focusing on elderly patients.
The average BMI of diabetic patients, in this study, was 32.5 kg/m2 (± 5.8) without significant correlation with the renal function (P value = 0.508). There are inconsistent results regarding the relationship between obesity and CKD, where many studies, like Framingham study [27], show a positive associated between BMI and CKD. Another study in UK showed that there is an increasing risk of CKD with increasing the weight [18]. In the other hand, a study in Thailand found a negative association between BMI and CKD, with which was owed to reverse causality where patients with advanced CKD may have a reduced BMI due to their disease [14]. These variations in results question the reliability of BMI for predicting CKD among diabetic patients. However, it should be noted that the BMI in the whole sample was high, which means that patients should be advised and counseled to lose more weight in the primary health care clinics.
HbA1c is a recommended standard of care to monitor diabetes. In this study, the mean HbA1c was 8.31%, but it was not significant to the presence of CKD (P value = 0.527). Increasing evidence shows a link between the glycemic environment and the renal damage. As in obesity, there are conflicting data regarding this association. A study in Spain showed that HbA1c levels were significantly higher among CKD diabetic patients (OR = 1.011, 95% CI 1.005–1.017, P < 0.001) [21]. However, other studies showed no significance increase in HbA1c level among CKD diabetic patients [20]. This results can be partially explained by the physiologic improvement of HbA1c due to the decreased insulin excretion by the kidneys in patients with impaired renal function [29].
In this study there was no association between gender and CKD (P value = 0.384). The relation between gender and CKD among diabetic patients is inconsistent in the literature. Many studies showed the female gender as a risk factor [11, 14, 19]; however, others reported the male gender as a risk factor[21]. This may be due the distribution of risk factors, like obesity and T2DM control status, between genders.
There were some limitations in this study. First, being a cross sectional study, not longitudinal, precludes any causal relationship between impaired renal function and their risk factors. Secondly, due to the low resources in the primary care settings there is a lack of data regarding proteinuria and renal biopsy which made it difficult to diagnose stage 1 CKD.
Including the diagnosis of CKD based on eGFR on multiple measures to establish chronicity, and conducting the study in PHC centers where almost all diabetic patients in Palestine receive, for free of charge, their preventive and curative services are the main strengths of our study.