THE AGING KIDNEY

An age-associated decrease in renal mass is common, although most studies done to explore this issue did not exclude individuals with comorbid conditions. Population selection and design type have limited the assessment of renal changes in the elderly, as many have used hospitalized or otherwise institutionalized elders in a cross-sectional design. Interestingly, in elderly patients who suffered traumatic death and in whom renal disease and/or important comorbid conditions were excluded, there was no significant decrease in renal mass. In patients with decreased renal mass, the number of functioning glomeruli decreases with a greater proportion lost in the cortex and relative sparing of medullary glomeruli. Although the number of glomeruli decline, the remaining glomeruli increase in size. Consequently, any injury to remaining nephrons is more consequential. There is an increase in glomerular hyalinization or sclerosis in apparently healthy elderly individuals. Once again, the change in the number of glomeruli varies greatly in elders, although the presence of glomerulosclerosis is indicative of subclinical renal injury from comorbid conditions affecting renal structure.

RENOVASCULAR CHANGES

There is a decrease in glomerular filtration rate (GFR) in elderly patients, although this may occur to a lesser extent in the aging of healthy individuals. Nevertheless, an age-related decline in GFR is an independent predictor of adverse outcomes such as death and cardiovascular disease. Blood flow decreases more than the GFR, leading to an increased filtration fraction and subsequent increase risk of nephron damage.

INTRODUCTION

Diabetes mellitus (DM) is a dominant chronic disease of older adults in the United States as well as in many other countries of the world. The prevalence of DM in the future is only expected to grow with the increase in the population of older adults, the prevalence of obesity, and physical inactivity. Clinicians will be faced with many unique challenges when caring for this older diabetic population. The clinician's major challenges are 1) to avoid symptoms and complications of hyper- and hypoglycemia, 2) to minimize or delay micro- and macrovascular complications, if possible, and 3) to maximize daily functioning. Underlying these challenges is the realization that the geriatric population is a heterogeneous one. Goals of care and treatment decisions may vary. These may depend less on the chronological age of the patient, although issues of life expectancy must be considered especially in the very old, but more so on the patient's functional abilities and on other comorbidities or coexisting geriatric syndromes. This chapter will focus on specific aspects of diabetes care in the older adult.

EPIDEMIOLOGY

An estimated 10.3 million people, or 20.9% of those 60 years of age or older, in the United States are afflicted with DM, the majority of whom have type 2 disease. Approximately half of Americans with diabetes are 60 years of age or older with an approximately even split between men and women. DM is more prevalent in minority groups.