Original Investigation
Pathogenesis and Treatment of Kidney Disease
CKD and Mortality Risk in Older People: A Community-Based Population Study in the United Kingdom

https://doi.org/10.1053/j.ajkd.2008.12.036Get rights and content

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 m2; 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 m2 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 m2. 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.

Section snippets

Methods

Full details of the trial have been reported previously.16, 17 In brief, the trial compared 2 methods of multidimensional assessment (universal versus targeted assessment) in people 75 years and older registered in 106 general practices selected from the Medical Research Council General Practice Research Framework in England, Wales, and Scotland, selected to be representative of the UK general practice standardized mortality ratios and Jarman deprivation score.18

All patients 75 years or older

Results

Median age of included participants was 80.2 years (interquartile range, 6.9), and 61% were women. Mean eGFR was 62.4 ± 14.9 (SD) mL/min/1.73 m2 in men and 55.8 ± 13.9 mL/min/1.73 m2 in women.

There were 82,562.5 years of follow-up, with a median of 7.25 years (interquartile range, 4.98). A total of 3,252 men (63.5%) and 4,381 women (54.4%) died, for a total of 7,633 deaths in 13,177 participants (57.9%). A total of 1,371 (42.2%) male deaths and 1,863 (42.5%) female deaths were attributed to CVD.

Discussion

We found that low eGFR was associated with greater all-cause and CVD mortality in community-dwelling older people. Effects were graded, independent of a range of sociodemographic and cardiovascular risk factors, and not explained by associations of low eGFR with anemia, high phosphate level, or low albumin level. Risks were more apparent in the first 2 years of follow-up, and the group with eGFR less than 30 mL/min/1.73 m2 had particularly high early mortality. The pattern differed by sex, with

Acknowledgements

We thank the anonymous referees for their constructive comments. A poster was presented at the European Renal Association Annual Conference, Stockholm, Sweden, May 10-13, 2008.

Support: The MRC Trial of Assessment and Management of Older People was supported by funds from the UK Medical Research Council, Department of Health for England and Wales and the Scottish Office. Support for the analyses presented here was provided by Kidney Research UK grant reference R/34/1/05. Dr Smeeth is supported

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    Originally published online as doi:10.1053/j.ajkd.2008.12.036 on April 27, 2009.

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