Worldwide, there are an estimated 200 million people with CKD who are vulnerable to the development of ESRD if no action is taken in the early stages to diagnose and treat them (22). ESRD is the tip of the iceberg and the total number of patients with CKD is considerably higher. It is important to study the prevalence of CKD in Palestine as it helps in the early detection and thus in the prevention and control of diabetic nephropathy..
This research was, to our best knowledge, the first epidemiological study on CKD prevalence in Palestinian primary care patients. 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(16). This research was nevertheless performed among patients with diabetic hypertensions and targeted patients with hospital diabetes, explaining the difference in prevalence. In addition, it only used one creatinine read that was presumably an acute instead of a chronic kidney injury.
Results on the prevalence of CKD among diabetic patients are variable; like Finland (16.2%) (21), Southern Ethiopia (23.4%) (23) Spain (27.9%) (20). Unfortunately, similar data from the surrounding countries is lacking. This variation on the prevalence of CKD among Diabetic patients is attributed to a difference in the definitions adopted and the characteristics of the studied populations.
In order to improve preventive and control measures, it is important to identify the risk factors associated with CKD, in particular the modifiable factors. The prevalence rate of HTN identified in this study among patients with type 2 diabetes (75%) was high. This is more than recorded in neighboring countries; Jordan (72.4%) (24), Qatar (64.5%) (25) and Saudi Arabia (53%) (26). This relatively higher rate of HTN may be attributed to the fact that most of the diabetic patients included in the study were obese and > 60 years of age.
This study showed a significant relationship (P Value < 0.001) between BP and kidney damage, represented by decreased eGFR as systolic BP increases (Table 2). Diabetic patients with HTN are more likely to develop CKD than diabetic patients with normal BP. These results are consistent with the literature of different countries (15,20,21). There is a significant overlap between HTN and CKD. A vicious cycle occurs where decreased kidney function causes an increase in BP and this increase can cause more kidney damage and a subsequent decrease in kidney function.
The high prevalence of HTN among our patients is worrying and should be taken into account, as several studies have documented the association between high BP and the development of ESRD. A Japanese study has shown that the risk of developing ESRD in high BP patients is 15 times higher, compared to controlled BP patients (27). This is important and more attention should be paid to better control of BP among diabetic patients.
Almost one-third of the patients (30.4%) were smokers; with a higher proportion of them among the CKD group (39.6%). In this study, smoking was correlated with renal function progression (P value= 0.022). The correlation between smoking and the occurrence of CKD in diabetic patients is clearer, with most research showing a substantial relationship between these two variables. Recently, two meta-analyses indicated evidence of cigarette smoking as an independent risk factor for CKD (14,28). Xia et al have reported that the risk of CKD was 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, all compared to never-smokers (14). The nephrotoxic effect of smoking, which involves endothelial cell dysfunction and increased resistance to insulin regardless of the diabetic condition, may explain this correlation. (14).
Age was found to be a significant risk factor (P value <0.001) for CKD. The overall high prevalence of CKD among elderly people can be explained by the steady decline in GFR with normal ageing, in addition to the high rate of comorbidities among this population, particularly hypertension and diabetes (29). It is also likely that, because of the increased involvement of this age group with the healthcare system, CKD is more readily diagnosed than other age groups. In addition, as shown in Table 2, a substantial decrease in eGFR has been recorded as age increases. These findings suggest the need for rigorous screening of diabetic patients with an elderly diabetic emphasis.
The average BMI of diabetic patients, in this study, was 32.5 kg/m2 (±5.8) without a significant correlation with the renal function (P value = 0.508). However, obesity is a main contributor to hypertension and diabetes (30). These two factors are well known risk factors for CKD, as several studies have shown that CKD patients have a higher prevalence of general and abdominal obesity than non-CKD patients (31–33). On the other hand, the lack of correlation in this study can be due to a limited number of sample size.
HbA1c is a recommended standard of care for the monitoring of diabetes. In this study, the mean HbA1c was 8.31%, but it was not significant to the presence of CKD (P value = 0.527). Growing evidence suggests that there is a correlation between the glycemic control status and renal damage. There are contradictory details on this relationship. A research 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)(20). However, other studies have shown that the CKD stages could influence the association between HbA1c and renal outcomes. A study in Taiwan, found that HbA1c >9% in CKD stages 3-4 was associated with increased risk for ESRD. Conversely, HbA1c is not a sufficient predictor of ESRD in patients with CKD stage 5 (34). This is presumably due to a marked drop in insulin clearance. In addition, the development of HbA1c is known to be lower in patients with CKD due to a decrease in red blood cells lifespan, as well as resistance of carbamylated hemoglobin molecules to glycosylation in a uremic molecules (35). Other reasons may be linked to improved treatment of diabetic patients with compromised renal function; more regular exposure to endocrine and nephrological interventions.
There was no correlation between gender and CKD in this study (P = 0.384). The relationship between gender and CKD among diabetic patients is inconsistent in the literature. Many studies have shown female gender as a risk factor (12,15,21), while others have reported male gender as a risk factor (20). This may be due to the gender distribution of risk factors, such as obesity and T2DM control status.
The key strengths of our research include the diagnosis of CKD based on eGFR on multiple measures to establish chronicity, and undertaking the study in PHC centers in which almost all diabetic patients in Palestine receive, free of charge, their preventive and curative services.
There were some limitations to this study. First, a cross-sectional, not longitudinal, analysis precludes any causal association between CKD and its risk factors. Second, due to low resources in primary care settings, there is a lack of data on albuminuria and renal biopsy that make it difficult to diagnose stage 1 CKD. Finally, the lack of full and up-to-date patient files on drugs made it difficult to determine its relationship with CKD.