Decreased eGFR in Older Adults with Hypertension and Diabetes

In older adults, serum creatinine levels may remain within reference limits while renal function is actually reduced 1
Creatinine-based equations can misclassify kidney disease by one stage in >30% of older participants due to reduced muscle mass, exercise, and meat intake 1

Physiological Kidney Aging

Hypertension and diabetes cause progressive reductions in renal blood flow through vascular glomerulosclerosis and interstitial fibrosis, which decrease GFR independent of acute tubular injury 1
Hypertension causes vascular glomerulosclerosis that reduces glomerular filtration 1
Diabetes produces interstitial fibrosis and reduces renal blood flow 1

ACE inhibitors and ARBs reduce intraglomerular pressure and can cause up to 30% elevation in serum creatinine from baseline without representing acute kidney injury 2
Diuretics reduce intravascular volume and renal blood flow, decreasing GFR hemodynamically 2
These medication effects represent functional rather than structural kidney changes and do not indicate progressive kidney disease when creatinine increases remain under 30% 2

Measure urinary albumin-to-creatinine ratio (UACR), as albuminuria ≥30 mg/g indicates kidney damage and dramatically increases cardiovascular risk even with preserved eGFR 3, 2
Consider using CKD-EPI cystatin C equations, which are more accurate than creatinine-based equations in older adults 1

Do not assume stable creatinine means stable kidney function in older adults—always calculate eGFR using validated equations that incorporate age 1
Do not discontinue ACE inhibitors or ARBs for creatinine increases up to 30% from baseline, as this does not represent acute kidney injury and these medications provide cardiovascular and renal protection 2
Screen for retinopathy in diabetic patients, as its absence with kidney disease suggests alternative causes requiring nephrology referral 3, 2

Normal GFR in young adults is approximately 120-130 mL/min per 1.73 m² and begins to decline with age 4, 5
Approximately 17% of persons older than 60 years of age have an estimated GFR less than 60 mL/min per 1.73 m² 4

Although age-related decline in GFR has historically been considered part of normal aging, decreased GFR in the elderly is an independent predictor of adverse outcomes including death and cardiovascular disease 4
Age-related GFR decline requires adjustment in drug dosages, just as in other patients with chronic kidney disease 4, 6
The definition of chronic kidney disease is the same regardless of age, despite the natural decline in GFR with aging 4, 5

Serum creatinine alone should not be used to assess kidney function, particularly in the elderly 6, 7
In the elderly, serum creatinine concentration does not accurately reflect the age-related decline in GFR due to concomitant age-related decline in muscle mass that reduces creatinine generation 8
For example, a serum creatinine level of 1.2 mg/dL may be associated with a creatinine clearance of 110 mL/min in a young athlete but only 40 mL/min in an elderly woman 6, 7

GFR estimation equations such as the MDRD study equation and Cockcroft-Gault formula incorporate age as a variable to account for age-related changes in kidney function 9, 10
These equations take into account serum creatinine concentration along with age, sex, race, and sometimes body size 9, 8