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Serum bicarbonate concentrations and kidney disease progression in community-living elders: the Health, Aging, and
Leonard Goldenstein1, Todd H Driver2, Linda F Fried3
1Division of Nephrology and Hypertension, Department of Medicine, University of California, San Diego, CA; Nephrology Section, Veterans Affairs San Diego Healthcare System, San Diego, CA.
Insights
Lower serum bicarbonate levels are linked to faster kidney function decline and increased risk of developing chronic kidney disease (CKD) in older adults. This finding may highlight a new target for preventing kidney disease progression.
Area of Science:
- Nephrology
- Geriatric Medicine
- Internal Medicine
Background:
- Chronic kidney disease (CKD) affects many older adults.
- Lower serum bicarbonate is linked to faster CKD progression in prevalent cases.
- The association between lower serum bicarbonate and incident CKD or progression in those with preserved kidney function is unknown.
Purpose of the Study:
- To investigate the association between serum bicarbonate levels and the risk of developing reduced estimated glomerular filtration rate (eGFR) and CKD progression in community-living older adults with predominantly preserved kidney function.
Main Methods:
- A longitudinal observational cohort study was conducted on well-functioning elders aged 70-79 years.
- Serum bicarbonate levels were measured using an arterial blood gas analyzer.
- Linear and logistic regressions analyzed associations between baseline serum bicarbonate and eGFR decline or incident eGFR < 60 mL/min/1.73 m(2).
Main Results:
- Participants with serum bicarbonate < 23 mmol/L showed a faster eGFR decline (0.55 mL/min/1.73 m(2) per year) compared to those with higher levels.
- Among those with baseline eGFR > 60 mL/min/1.73 m(2), lower bicarbonate levels were associated with nearly 2-fold increased odds of developing incident eGFR < 60 mL/min/1.73 m(2).
Conclusions:
- Lower serum bicarbonate concentrations are independently associated with eGFR decline and incident reduced kidney function in older community-dwelling individuals.
- Serum bicarbonate levels may offer insights into kidney tubule health in individuals with preserved eGFR.
- These findings suggest serum bicarbonate could be a potential target for interventions aimed at preventing CKD development.
Background:
In populations with prevalent chronic kidney disease (CKD), lower serum bicarbonate levels are associated with more rapid CKD progression, but whether lower bicarbonate levels also are associated with risk of incident estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m(2) and CKD progression among community-living persons with predominantly preserved kidney function is unknown.
Study Design:
Longitudinal observational cohort study.
Setting & Participants:
Well-functioning community-living elders aged 70-79 years at inception.
Predictor:
Serum bicarbonate level measured at the time of collection by arterialized venous blood sample using an arterial blood gas analyzer.
Outcomes:
Change in eGFR over 7 years, and new eGFR < 60 mL/min/1.73 m(2) with a rate of loss of at least 1 mL/min/1.73 m(2) per year.
Measurements:
Linear and logistic regressions were used to evaluate associations of baseline serum bicarbonate level with change in eGFR and incident eGFR < 60 mL/min/1.73 m(2).
Results:
At baseline, mean eGFR was 84 ± 16 (SD)mL/min/1.73 m(2), and serum bicarbonate level was 25.2 ± 1.9 mmol/L. Compared with participants with higher bicarbonate concentrations (23.0-28.0 mmol/L), those with bicarbonate concentrations < 23 mmol/L (n = 85 [8%]) lost eGFR0.55 (95% CI, 0.13-0.97) mL/min/1.73 m(2) per year faster in models adjusted for demographics, CKD risk factors, baseline eGFR, and urine albumin-creatinine ratio. Among the 989 (92%) participants with baseline eGFRs > 60 mL/min/1.73 m(2), 252 (25%) developed incident eGFRs < 60 mL/min/1.73 m(2) at follow-up. Adjusting for the same covariates, participants with bicarbonate concentrations < 23 mmol/L had nearly 2-fold greater odds of incident eGFRs < 60 mL/min/1.73 m(2) (OR, 1.72; 95% CI, 0.97-3.07) compared with those with higher bicarbonate concentrations.
Limitations:
Only 2 measurements of kidney function separated by 7 years and loss to follow-up due to intervening mortality in this elderly population.
Conclusions:
Lower serum bicarbonate concentrations are associated independently with decline in eGFR and incident eGFR < 60 mL/min/1.73 m(2) in community-living older persons. If confirmed, serum bicarbonate levels may give insight into kidney tubule health in persons with preserved eGFRs and suggest a possible new target for intervention to prevent CKD development.
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