1983

CAUSES OF DEATH IN ELDERLY versus youngerPATIENTS WITH CHRONIC KIDNEY DISEASE

Chiu D, Abeygunarathne, T, Ritchie, J, Alderson, H, Sinha, S, Kalra PA, Green D

Institute of Population Health, The University of Manchester, UK

INTRODUCTION:Mortality increases with age in chronic kidney disease (CKD). We hypothesised that the most common causes of death in older patients (≥65years) are different tothe young (65years) becausethe co-morbidity profile ofCKD changes with age.

METHODS:This was a sub-study of the Chronic Renal Insufficiency Standards Implementation Study (CRISIS), a prospective longitudinal cohort study ofpatients with eGFR<60mL/min managed in a tertiary nephrology unit. Patients were categorised according to age (<65 years versus ≥65 years) and a comparison of co-morbid status made between groups using independent samples T-test or Fisher Exact Test. Mortality rates were expressed as events per 1000 patient years, and rates compared between age groups expressed as relative risk (RR) in elderly versus younger patients. Coded cause of death data were obtained from the Office of National Statistics, and categorised as cardiac, other vascular deaths, infection, malignancy, renal failure, other, and unknown usingICD-10 codes.

RESULTS: 2130 patients were included in the study. Median follow up = 42 months (interquartile range 19-68), with689 deaths (557 in ≥65 years, 132 in <65 years). Population demographics are compared in table 1. The RR for death aged≥65years compared with <65years group was 4.3. Cardiovascular and malignant mortality increased proportionately to this in older patients. Infection rose disproportionately as a cause of death (RR = 6.3). The most frequent cause of death from infection was pneumonia (28%). RR for death are summarised in table 2.

Table 1. Demographics comparing older versus younger patients.

<65 years (n=927) / ≥65years(n=1203) / p
Mean Age (years) / 51.8±10.9 / 74.8±5.9 / <0.01
Mean eGFR (mL/min/1.73m2) / 35.2±17.7 / 30.7±13.9 / <0.01
Male (%) / 60 / 64 / 0.21
Systolic blood pressure (mmHg) / 135.0±20.8 / 140.7±21.6 / <0.01
Diabetes Mellitus (%) / 28 / 35 / <0.01
Ischemic heart disease (%) / 15 / 41 / <0.01
Heart failure (%) / 47 / 57 / <0.01

Table 2. Comparing mortality rates in the most common causes of death in young and old CKD patients (death rates expressed as deaths per 1000 patient years, RR=relative risk).

<65 years (n=132) / ≥65years
(n=557) / RR (Elderly/young)
All-cause / 31 / 131 / 4.2
Cardiac / 7 / 30 / 4.3
Vascular / 2 / 8 / 4.0
Infection / 4 / 25 / 6.3
Malignancy / 3 / 11 / 3.7
Renal Failure / 1 / 9 / 9.0

Conclusion: The causes of death profile is different in younger versus elderly CKD patients, acknowledging that the co-morbidity profiles differ.The increase in rate of cardiovascular death in older patients is disproportionate to the increase in cardiovascular co-morbidity. Mortality rate was 9 times greater in aged≥65years dying from renal failure, possibly due to more choosing conservative treatment.Infection is significantly more common than expected in the elderly. Focus towards prevention of infection may become increasingly important in an aging CKD population.