C ONCLUSIONES DEL C APÍTULO

3.4.1 Demographics of ESRD cohort

The ESRD cohort included 44,922 treated ESRD patients identified over the 40 year period of which 2,192 patients were identified from ORLS and 42,970 from all-England HES, including 2,328 from HES Oxford (Figure 3-1 & Table 3-1).

Age

The median age of patients starting RRT in Oxfordshire rose by 18 years; from 49 years (interquartile cut offs, 36-60) in 1970-1990 to 61 years (46-72) in 2006-2008. If the initial year group were divided, it is apparent that this increase began early; median age increased from 46 years in 1970-1985 to 56 years in 1986-1990, and 59.5 years in 1994-1996 (Figure 3-2).

Consequently, in 1970-1990, only 25% of new patients were older than 60 years compared to nearly 50% of patients from 2000 onwards. Similarly, between 1970 and 1990 the proportion of patients commencing RRT who were ≥70 years was 8.2%, increasing to nearly one third by 2006-2008. Similar trends were observed in HES Oxford and in all-England data from 2000 (Table 3-1).

Gender

There has been no significant change in the overall proportion of females across the entire ESRD cohort, contributing approximately 40% across both cohorts (p for trend over time = 0.20 for ORLS/HES Oxford and p=0.50 for all-England-HES) (Figure 3-2 & Table 3-1).

Ethnicity

Ethnicity data were not reliably recorded in ORLS. From 2000-2008 the proportion of HES Oxford patients with any known ethnicity increased from 81.3% to 96.0%. Of those with a

recorded ethnicity the proportion of non-whites increased from 13.2% in 2000-2002 to 15.9%

in 2006-2008 but patients of white ethnicity predominated in all year groups at between 84-86%. In all-England HES data, of these patients with known ethnicity, approximately 80%

were of white ethnicity. There were, on average, greater proportions of Blacks (6.6% vs 4.0%) and South Asians (8.5% vs. 7.0%) recorded in all-England HES than HES Oxford (Table 3-1).

Socio-economic status

In HES Oxford, the largest proportion of patients was identified from the highest IMD quintile (43-45%) with nearly two thirds of patients consistently being derived from the two most affluent quintiles. The SES structure in HES Oxford remained largely unchanged between 2000 and 2008. The SES structure in all-England stood in contrast where there was a more even distribution of patients across each IMD quintile. The proportions of patients from each IMD quintile were very different in HES Oxford compared to all-England, reflecting that Oxfordshire includes many districts that were classified as ‘least deprived’. The distribution of patients from the each IMD quintiles did not appear to change over the decade of all-England HES.

Comorbidity

The reported prevalence of baseline major comorbid illness all increased significantly over time across the Oxfordshire cohort over time. The proportion of patients with diabetes was 5.8% between 1970 and 1985, increasing to 8.1% by 1986-1990, then doubling to 16.8% by 1991-1996 and it then doubled again by 2006-2008 (Figure 3-2). Overall the prevalence of diabetes it increased over 4-fold from 6.7% in 1970-1990 to 33.9% in 2006-2008 (Table 3-1).

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Prior vascular disease nearly trebled, from 9.1% in 1970-1984 to 25.2% in 2006-2008. This constituted rises in peripheral vascular disease from 3.0% to 12.9%, major coronary disease from 2.6% to 8.3%, congestive heart failure from 5.2% to 10.5% and cerebrovascular disease from 1.4% to 3.5%.

The proportion of new ESRD patients with non-vascular comorbidities increased from 7.8%

in 1970-1990 (and even lower at 5.5% in 1970-1985, (Figure 3-2) to 24.9% in 2006-2008 which largely constituted a rise in the prevalence of COPD (1.3% to 10.3%) and smaller increases in the prevalence of all other non-vascular comorbidities: cancer (2.9% to 7.6%), connective tissue disease (2.0% to 4.9%), liver disease (0.5% to 2.3%), peptic ulcer disease (1.6% to 1.9%) and hemi-paraplegia (0.2% to 1.5%).

A summary of baseline comorbidities are presented in Table 3-1 and graphically in Figure 3-2.

Figure 3-2: Baseline characteristics of new treated end-stage renal disease patients, by year

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Table 3-1: Baseline characteristics of new treated end-stage renal disease patients, by region and year

Renal Characteristics of the derived ESRD cohort

Initial RRT modality

The data suggested that the proportion of patients identified as commencing maintenance RRT via dialytic therapies has reduced, on absolute scale, by 3.4%: from 94.6% in 1970-1990 to 91.2% in 2006-2008 with a reciprocal increase in the proportions of patients identified as starting with a transplant, from 5.4% to 8.4%. This observed pattern of an increasing proportion of pre-emptive transplantation in HES Oxford was similar to that in all-England, yet the proportions of patients identified as starting maintenance RRT with a transplant in all-England were, on average, lower. The test for trend across the year groups of was non-significant in Oxford, p = 0.08 but in all-England, where there were many more pre-emptive transplants performed, a significant trend was identified, p= 0.002 (Table 3-1).

Presumed primary renal disease

The proportion of patients with an identifiable ‘presumed’ PRD increased over time, from 21.5% in 1970-1990 to 46.9% in 2006-2008. The proportion of ESRD patients with a presumed PRD of diabetic kidney disease rose from 1.6% in 1970-1990 to 22.1% in 2006-2008. The proportion with presumed glomerulonephritis as the cause of ESRD was 9.3% in 1970-1990, rising to 14.5% by 2006-2008. The proportion of patients with polycystic kidney disease fell slightly from 10.5% in 1970-1990 to 8.4% by 1991-1996, 8.6% by 2000-2002, and 7.5% in 2003-2005 before increasing back to 10.4% by 2006-2008.

All-England data were similar to HES Oxford with roughly one fifth of patients having diabetic kidney disease, 8-10% having polycystic kidney disease with a little over 50% having other known or unknown diagnoses (Table 3-1).

The difficulties in consistently identifying primary renal diagnosis, especially in ORLS with upto three quarters not being able to be identified, limited its use as variable to take forward

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the general population. ESRD data repositories have substituted knowledge of prior co-morbid illnesses at the start of a RRT career with PRD to use as co-variable in mortality analyses but as 10-15% of patients have an unknown aetiology of ESRD and you cant have more than one PRD (you couldn’t have PKD and diabetes) then there are obvious limitations.

3.4.2 Stratified baseline characteristics within ESRD cohorts; by initial RRT modality

In the period covering ORLS, pre-emptive transplants were relatively uncommon with only 66 performed between 1970-1990, equating to 3.3 per annum (p.a.) and then 72 in the subsequent 6 years between 1991-1996, equating to 12/pa. In HES Oxford, the absolute numbers of pre-emptive transplant recipients continued to increase to 44 (14.7/pa) in 2000-2002, to 55 (18.3/pa) in 2003-2005 and 74 in 2006-2008 (24.6/pa). Patients who were identified as receiving a kidney transplant as their initial modality of RRT were more likely to be younger, less morbid than those starting on dialytic therapies (Table 3-2 & Table 3-3).

Pre-emptive transplant recipients had a median age at start of RRT of 36, (IQR, 26-45) rising to 45 (from 2000) compared to dialysis patients who had a median age of 50 (37-61) in 1970-1990 rising to 62 (49-73) by 2006-2008 (Table 3-2 & Table 3-3). The proportion of females who were identified as receiving a transplant as their initial mode of RRT was, in general, lower than that those starting via dialysis but remained fairly static over the period of the cohort (Table 3-2 & Table 3-3).

The IMD quintile of patients who received a transplant as their initial RRT modality both in Oxford and all-England were more likely to come from less deprived areas than those starting on dialysis. Of all-England patients identified as receiving a transplant as their initial RRT, the proportions residing from the most deprived (IMD 1) districts fell from 16.4% to 12.6% (Table 3-2 & Table 3-3).

The prevalence of major comorbidities was considerable less in patients identified as having a transplant as opposed to dialysis. Vascular disease among those who received a

pre-emptive transplant had on average, a 5.7% prevalence, compared to 28.1% in patients starting on dialytic therapies. Non-vascular disease was identified in 11.2% of those receiving pre-emptive transplants as opposed to 25.8% in those that started via dialytic therapies (Table 3-2 & Table 3-3).

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Table 3-2: Baseline characteristics of new treated end-stage renal disease patients with transplantation being the first recorded modality of renal replacement therapy

Table 3-3: Baseline characteristics of new treated end-stage renal disease patients in which dialysis was the first recorded modality of renal replacement therapy

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3.4.3 Demographics of general population hospital controls

The general population hospital control cohort consisted of 5,613,781 patients who entered the cohort at the time of a minor condition or procedure. This 5.6 million included 532,019 patients identified in the ORLS (1970-1996) and 5,081,762 patients from all-England HES between 2000-2008, of which 253,069 patients were from HES Oxford (Figure 3-1 & Table 3-4).

Age

The median age of patients at entry into the Oxfordshire general population cohort rose by seven years from 40 years (29-57) in 1970-1990 to 47 years (33-64) in 2006-2008.

Compared to the ESRD cohort, the age structure of the general population controls therefore did not change to the same magnitude. Nevertheless, the proportion of patients over 60 years increased from a quarter to one third between 1970-1990 and 2006-2008, whilst the proportion of patients over 70 years increased by about a half from 12.5% in 1970-1990 to 19.0% in 2006-2008 (Table 3-4).

However even within the general population the prevalence of comorbidities increased substantially.

The prevalence of diabetes rose 4-fold in the hospital controls from 0.8% in 1970-1990 to 4.1% in 2006-2008 (Table 3-4).

The proportion of general population controls identified as having baseline vascular disease increased from 2.0% in 1970-1990 to 3.6% in 2006-2008. This constituted a doubling of the reported prevalence of major coronary disease (0.6% to 1.2%), congestive heart failure (0.6% to 1.2%) and cerebrovascular disease (0.4% to 0.8%) and a more modest increase in peripheral arterial disease, from 0.6% to 1.0%. General population control patients identified from HES Oxford data had, in general, a 20-30% lower proportion than that in all-England patients, but yet there were similar increases were in Oxford and all-England patients over time (Table 3-4).

The prevalence of comorbidities which saw the largest absolute increases were serious non-vascular disease, rising by 6.2% from 3.6% in 1970-1990 to 9.8% in 2006-2008. Increases in prevalence of COPD constituted, by far, the largest portion of this observed increase, rising about six-fold from 0.9% to 6.3% (Table 3-4).

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Table 3-4: Baseline characteristics of general population hospital controls, by year