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 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.

Index Words: Chronic kidney disease, mortality, survival, older people