Department of Nephrology, Hospital General `Gregorio Marañon', Madrid, Spain
Sir,
To evaluate the outcome of diabetic patients on renal replacement therapy (RRT) we studied all diabetic end-stage renal failure (ESRF) patients treated in our Hospital from 1978 to 1998. Three years ago we reported a similar study up to 1995 [1].
Diabetes mellitus has become the leading cause of ESRF in our health area of Madrid; 30% of all cases of ESRF. The incidence of diabetics starting RRT was 33.3 per million population (pmp) in 1998, while in 19931994 diabetes was 15% and 21% pmp, respectively (Table 1). The number of diabetics on RRT in 1998 was 135 pmp, with an a overall prevalence of 1054 pmp. The proportion of diabetics on RRT increased from 7.4% in 1986 to 12.7% in 1998. At the same time, the proportion of incident type 2 diabetics/diabetics on RRT increased from 15% in 19871988, to 54% in 19931994 and to 81% in 19971998. Consequently, the mean age of diabetic patients starting RRT increased from 47 years old before 1988, to 58 in 19891990 and 63 in 19971998 (Table 1
).
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During the mean follow-up period (51±45 months) 79 patients changed their treatment modality and 45 of them received a kidney allograft. The relative risk of drop-out was higher with CAPD technique when compared to HD. Frequent clinical complications were: ocular (77%), cardiovascular (myocardial infarction 17%), acute cerebrovascular disease (21%), distal angiopathy (35%) and 10% amputation.
By December 1998, 89 patients had died, eight patients were lost for follow-up and 85 patients continued on treatment. Cardiovascular and cerebrovascular diseases (29%) and infections (27%) were the two most frequent causes of death. Death of unknown-causes represented 19% of all deaths. The overall survival (Kaplan Meier) was 92%, 80%, 72%, 61% and 54% at 1, 2, 3, 4 and 5 years, respectively (57 patients completed the last period). Survival was better on HD than on CAPD, but without statistical significance, although there was significant difference in age and in proportion of type 2 diabetes between both groups. Data analysis estimated by Cox proportional hazards regression showed that younger age and kidney transplantation had a positive independent effect on survival, while clinical distal angiopathy had a significant negative effect on survival. Ischaemic cardiopathy did not have an independent effect on survival. This difference with respect to distal angiopathy may be explained by the effective diagnostic and treatment programme for ischaemic cardiopathy at our hospital.
In 1994, the annual incidence of ESRD from diabetes mellitus was 70 patients pmp in the US, compared to 198 patients pmp per year with ESRD overall. These figures represent 35% of all new admissions for RRT for diabetes during that year. In the period 19921996 [2] 39.2% of new patients were diabetic. The incidence in Europe remained lower than in the US during the same period, but showed a continuous increase although with great variations between the different European countries [3]: 10.4 diabetics pmp in Lombardia and 52 in lower Neckar, Germany. Our incidence is intermediate between both figures but higher than that of other areas in Spain [4], except for the Canary Islands. There is a relationship between the incidence and the proportion of type 2 diabetes/diabetes admitted for RRT: 48% in Lombardia, 90% in Lower Neckar Germany and 81% in our data [2].
What are the causes of the rising number of ESRF in patients with diabetes and the geographical variations? Firstly, the prevalence of type 2 diabetes in the population is on the increase, partially because of the ageing of society, economic improvement and a sedentary lifestyle [5]; secondly, survival in type 2 diabetic patients has improved continuously in the last decade; thirdly, the growing widespread availability of RRT and acceptance of elderly patients for this therapy has increased. Genetic, ethnic, nutritional aspects and lifestyle may partially explain the different incidences of ESRF in diabetics between the European countries, but all these factors cannot have changed significantly enough in 10 years to explain such a marked increase in differences between bordering geographical areas. Different developments in health care may play an important role in this question. If that is true, the differences in the incidence will become less significant in the next years.
The 5-year survival rate in this group of diabetic patients is 1020% better than that of other reports [3,4,6,7]. The cause of that result may be due to a higher proportion of diabetic patients with a kidney allograft and a lesser proportion of elderly patients on CAPD; the concept of `integrated RRT' for diabetics is also very important. Diabetics on RRT need to change frequently from one modality of treatment to another, from CAPD to haemodialysis, etc. Early treatment of clinical complications and a preventive policy regarding vascular access complications are also of considerable influence [8]. The characteristics of haemodialysis treatment in our hospital are: high quality dialysate with bicarbonate; 70% of highflux dialysers; 40% AFB in hospital unit; Kt/V higher than 1.2 (Sargent, Gotch) or 1.35 (Daugirdas II); dialysis duration between 3 and 4 h per session and most important, the achievement of good tolerance. AFB allows better control of acidbase metabolism, nutritional status and tolerance than bicarbonate haemodialysis in diabetics [9].
Micro and macroangiopathy remain the major clinical problem in diabetics on RRT, which affect the morbidity and mortality rates of these patients. In our experience distal angiopathy is a significant mortality risk factor. New strategies for the prevention of angiopathy and nephropathy in diabetic patients are necessary.
References