CKD and mortality risk in older people: a community-based population study in the United Kingdom.

BACKGROUND: The prevalence of chronic kidney disease (CKD) increases with age; however, the prognostic significance in older people is uncertain. This study aims to determine the association of CKD with all-cause and cardiovascular mortality in community-dwelling older people 75 years and older. STUDY DESIGN: Cohort study of people 75 years and older recruited in 1994 to 1999 to 1 arm of a trial of multidimensional health assessment with mortality follow-up. SETTING & PARTICIPANTS: 53 general practices in Great Britain. 15,336 (73%) of those eligible participated. 13,177 (86%) had serum creatinine measured at baseline. MAIN FACTOR: Estimated glomerular filtration rate (eGFR). OUTCOMES: All-cause and cardiovascular mortality. MEASUREMENTS: eGFR derived from serum creatinine level using the 4-variable Modification of Diet in Renal Disease (MDRD) Study equation in milliliters per minute per 1.73 m(2); dipstick proteinuria. Mortality by linkage to national death registration and death certification. RESULTS: After a median follow-up of 7.3 years (interquartile range, 5.0), 7,633 (58%) had died, 42% of cardiovascular causes. In the first 2 years of follow-up, adjusted hazard ratios for all-cause mortality in eGFR bands of 45 to 59, 30 to 44, and less than 30 compared with eGFR greater than 60 mL/min/1.73 m(2) were 1.13 (95% confidence interval, 0.93 to 1.37), 1.69 (95% confidence interval, 1.26 to 2.28), and 3.87 (95% confidence interval, 2.78 to 5.38) in men and 1.14 (95% confidence interval, 0.93 to 1.40), 1.33 (95% confidence interval, 1.06 to 1.68), and 2.44 (95% confidence interval, 1.68 to 3.56) in women, respectively. Hazard ratios were greater for cardiovascular mortality and lower after 2 years. Dipstick proteinuria was independently associated with all-cause, but not cardiovascular, mortality risk in both sexes. LIMITATIONS: Single serum creatinine measurement, no calibration of serum creatinine, MDRD Study equation not validated in older people. CONCLUSION: As kidney function decreases, there is a graded and independent increase in all-cause and cardiovascular mortality risk in older people 75 years and older, especially in men and those with eGFR less than 45 mL/min/1.73 m(2). Dipstick proteinuria did not add to cardiovascular mortality risk in this elderly population. In older people, identification and management of CKD should prioritize the smaller numbers with more severe CKD.

Detecting chronic kidney disease in older people; what are the implications?

BACKGROUND: national policy is focused on early identification, referral and management of chronic kidney disease (CKD) to prevent both progression to endstage renal failure and cardiovascular disease. However, the significance of identifying CKD in older people is unclear. OBJECTIVE: to determine the frequency of CKD in older people using estimated glomerular filtration rate (eGFR), and its associations with morbidity and functional measures. DESIGN: observational cross-sectional analysis of baseline data from a large cluster randomised trial of health and social assessment of older people in the community. SETTING: included 53 general practices in Great Britain. SUBJECTS: subjects were people aged 75 and over, living in the community participating in the trial arm where systematic blood testing was undertaken. METHODS: the response rate for participation at baseline assessment of those eligible was 73% (15,536/20,934), of whom 13,109 (86%) participants had a serum creatinine measured, and an eGFR derivable using the Modification of Diet in Renal Disease formula (MDRD) in ml/min/1.73 m(2). Key outcomes were the prevalence of CKD stages and their associations with morbidity and functional status. RESULTS: prevalence of CKD was 56.1% (95% CI 55.3-57.0) for eGFR < 60, 17.7% for eGFR < 45 (95% CI 17.1-18.4), and 2.7% (95% CI 2.4-2.9) for eGFR < 30. It was higher in older ages, females, and those with cardiovascular comorbidity and doctor-diagnosed hypertension but not with diabetes. The strength of the association with measures of morbidity and functional impairment increased as eGFR fell, especially once the eGFR was < 45. For example, the odds ratios in males for anaemia for an eGFR < 30, 30-44 and 45-59 versus reference GFR > 60 were 8.3 (5.1-13.7), 3.0 (2.1-4.2) and 1.2(0.8-1.7) respectively; similar figures for partial dependence on activities of daily living were 2.2 (1.4-3.3), 1.6 (1.2-2.1) and 1.0 (0.9-1.3) and for lack of physical activity 2.20 (1.39-3.48), 1.78 (1.37-2.32) and 1.10 (0.92-1.32). CONCLUSIONS: an eGFR < 60 is very common in older people. An eGFR < 45 identifies a smaller sub-group of older people with significant comorbidity, impaired functional state and a high risk of potentially reversible consequences such as anaemia. The benefits of identifying older people with an eGFR > 45 need to be determined.