Academic Geriatric Resource Center
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AT A GLANCE

Glossary

0. Introduction
1. Demography And Epidemiology
1.1 The Changing Face of Aging: Objectives
1.2 Local and Regional Variations Among Older Adults in the United States
1.3 Implications of an Aging Society for Health Care Needs and Resources
1.4 Common Chronic Conditions Associated with Advanced Age
1.5 Post Test
2. Biology and Physiology of Aging
2.1 Introduction and Background
2.2 Theories of Aging
2.3 Physiological Changes with Aging
2.3.1 Loss of Homeostatic Reserve--Hyperthermia
2.3.2 Loss of Homeostatic Reserve--Hypothermia
2.3.3 Vulnerability of Older Adults to Hypothermia
2.3.4 Clinical Importance of Vulnerability to Hypothermia
2.3.5 Loss of Homeostatic Reserve--Other Examples and Clinical Implications
2.3.6 Clinically Important Age-Related Changes in Organ Systems
2.3.7 Clinically Important Age-Related Changes in the Renal System
2.3.8 Clinical Significance of Age-Related Changes in Renal System
2.3.9 Clinically Important Age-Related Changes in the Cardiovascular System
2.3.10 Clinical Significance of Age-Related Changes in the Cardiovascular System
2.3.11 Clinically Important Age-Related Changes in the Pulmonary System
2.3.12 Clinical Significance of Age-Related Changes in the Pulmonary System
2.3.13 Age-Related Changes in the Neurologic System
2.3.14 Clinical Significance of Age-Related Changes in the Neurologic System (I)
2.3.15 Clinical Significance of Age-Related Changes in the Neurologic System (II)
2.3.16 Clinically Important Age-Related Changes in the Gastrointestinal System
2.3.17 Clinical Significance of Age-Related Changes in the Gastrointestinal System (I)
2.3.18 Clinical Significance of Age-Related Changes in the Gastrointestinal System (II)
2.3.19 Clinically Important Age-Related Changes in the Immune System
2.3.20 Clinical Significance of Age-Related Changes in the Immune System
2.3.21 Clinically Important Age-Related Changes in the Endocrine System (I)
2.3.22 Clinically Important Age-Related Changes in the Endocrine System (II)
2.3.23 Clinical Significance of Age-Related Changes in the Endocrine System
2.3.24 Clinically Important Age-Related Changes in the Musculoskeletal System
2.3.25 Clinical Significance of Age-Related Changes in the Musculoskeletal System (I)
2.3.26 Clinical Significance of Age-Related Changes in the Musculoskeletal System (II)
2.3.27 Clinically Important Age-Related Changes in the Genitourinary System (I)
2.3.28 Clinically Important Age-Related Changes in the Genitourinary System (II)
2.3.29 Clinical Significance of Age-Related Changes in the Genitourinary System
2.3.30 Clinically Important Age-Related Changes in the Sensory Systems
2.3.31 Clinical Significance of Age-Related Changes in the Sensory Systems (I)
2.3.32 Clinical Significance of Age-Related Changes in the Sensory Systems (II)
2.3.33 Clinically Important Age-Related Changes in the Integument
2.3.34 Clinical Significance of Age-Related Changes in the Integument
2.4 Pharmacologic Considerations
2.5 Post Test
3. Socio-cultural And Psychologicial…
3.1 Module Objectives
3.2 Social Theories of Aging
3.3 Psychological Development In Late Life
3.4 Ethno-Cultural Issues And Age-Stratified Societies
3.5 Late-Life Transitions
3.6 Dependent Elders: Special Concerns
3.7 Cultural Views of Death
3.8 References
3.9 Post Test
4. Assessment Of The Geriatric…
4.1 Module Objectives
4.2 Domains of Assessment: Functional Assessment
4.2.1 How to Use Information from a Functional Assessment
4.2.2 Vision Impairment
4.2.3 Hearing Impairment (I)
4.2.4 Hearing Impairment (II)
4.2.5 Oral and Dental Health
4.2.6 Introduction to Oral Health Assessment
4.2.7 Oral Health Assessment
4.2.8 Common Oral Conditions in Older Adults: Tooth Loss (I)
4.2.9 Common Oral Conditions in Older Adults: Tooth Loss (II)
4.2.10 Common Oral Conditions in Older Adults: Care of Dentures
4.2.11 Common Oral Conditions in Older Adults: Dental Decay
4.2.12 Common Oral Conditions in Older Adults: Periodontal Disease
4.2.13 Common Oral Conditions in Older Adults: Candidiasis Infection
4.2.14 Common Oral Conditions in Older Adults: Leukoplakia and the Risk for Oral Cancer
4.2.15 Guidelines for a Dental Referral
4.2.16 Falls and Gait Assessment
4.2.17 Assessing for Falls
4.2.18 Techniques for Gait Assessment
4.2.19 Gait Assessments and Falls Interventions
4.2.20 Risk Factors for Falls and Targeted Interventions
4.2.21 Modification of Risk Factors: Ability to Get Up After a Fall
4.2.22 Modification of Risk Factors: Fracture Risk
4.2.23 Modification of Risk Factors: Anticoagulation
4.2.24 Incontinence
4.2.25 Skin Breakdown: Pressure Ulcers
4.2.26 Cognition/Dementia
4.2.27 Benefits of Early Detection of Dementia
4.2.28 Screening Techniques for Dementia
4.2.29 Decision-Making about Dementia Screening
4.2.30 Nutrition
4.2.31 Alcohol Use and Alcoholism
4.2.32 Medication and Complementary Therapies
4.2.33 Case Example: Mr. Singh
4.2.34 Mr. Singh--Use of Herbal Medicines
4.2.35 Mr. Singh--Possible Interventions
4.2.36 Mr. Singh--Concerns about Marathon Running at 92?
4.2.37 Mr. Singh--Considerations for Patient/Family Well-Being
4.2.38 Assessing for Polypharmacy (I)
4.2.39 Assessing for Polypharmacy (II)
4.3 Domains Of Assessment: Psychosocial Health And Functioning
4.4 Special Considerations In Assessment
4.5 Post Test
5. Health Care Policies
5.1 Module Objectives
5.2 The Policy-Making Process
5.3 Financing Health & Long Term Care
5.4 Quality Of Care Issues In Long Term Care
5.5 Need And Access Across The Spectrum Of Care
5.6 References
5.7 Post Test
6. Exploring Age-Related Body…
6.1 Cardiovascular System
6.2 Endocrine System
6.3 Immune System
6.4 Musculo-Skeletal System
6.5 Neurological System
6.6 Renal System
6.7 Post Test

Module 6: Exploring Age-Related Body Systems Changes

6.6: Renal System



6.6.5: Renal Changes with Age

Renal mass declines about 20% between the ages of 40 and 80. Loss in mass is predominant in the renal cortex and includes a decrease in functioning glomeruli and telomere DNA (Melk, 2000). (Also see the Telomere Theory of Aging—Note: This link will open in a new browser window.)

Renal blood flow (RBF) also decreases, about 10% per decade after the age of 20. By age 80, RBF may be 600ml/min as compared to 1200ml/min in young adults (30-40). Like changes in mass, this is most prominent in the cortex. The decrease in RBF does not appear to be just related to a change in renal mass because there appears to be an actual decrease in flow per gram of tissue (Rowe, 1988; Beck, 1998).

Animal data suggest the following:

  • Cortex: atrophy of afferent and efferent arterioles of the glomerular tuft
  • Medulla: sclerosis resulting in the formation of direct channels between the afferent and efferent arterioles.

Arteriole Communication (image)

These changes maintain blood flow to the medulla over that of the cortex. How does this affect renal function?

The highly concentrated medulla, maintained by a sluggish blood flow, allows the kidney to form concentrated or dilute urine. An increased rate of blood flow to the medulla can ‘wash out’ some of the hypertonicity, decreasing the concentrating capacity of the counter current mechanism.

Other structural changes, some of which are from animal data, are noted in Table 1:

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Table 1: Renal Changes with Age

(a decrease in) functional glomeruli (leads to) (an increase in) size of remaining glomeruli

(a 
decrease in) in the # and % of epithelial cells

(a 
decrease in) telomere DNA - mainly in the cortex

(an 
increase in) # of mesangial cells and (an increase 
in) thickening of the basement membrane of the tubules

Diverticuli in the distal convoluted tubules

? change in permeability

Why do these structural changes occur? We don’t know for sure yet, although some researchers have investigated possible reasons, including hypertenion and diet. Nor do we know whether it is possible to avoid these changes. However, we do know that there is heterogeneity in actual renal function in older adults.

Some suggest the changes in renal structure are caused by increases in blood pressure (Tracy, et al., 1992); others suggest the high protein diet often consumed in Western societies (Brenner, et al. 1989; Anderson and Brenner, 1988). A high protein diet could lead to chronic hyperperfusion of the kidney and thus hyperfiltration, which would in turn possibly potentiate renal deterioration. However, much of these data come from animal research and are not proven. Hyperperfusion may be an adaptive mechanism that maintains renal function with age (Lindeman, 1998). Further, a recent cross sectional study comparing 29 individuals in Boston (age range 19-79, x=52) with 16 island dwelling indigenous Kuna Amerinds of Panama (age range 18-86, x=51) who consume a low protein diet and did not evidence the same increase in blood pressure with age found that both groups had similar declines in GFR and renal perfusion with age; the Kuna Amerinds actually evidenced a steeper decline, although the actual differences in the rate of decline were not statistically different (Hollenberg et al. 1999).

What are the functional implications of the structural changes?

The most important change is a Decrease in Glomerular Filtration Rate (GFR is defined as—filtration of plasma/unit of time; about 125ml/min. or about 180L/day in a young, healthy kidney. However, there is wide inter-individual variation, and over 99% of the glomerular filtrate is reabsorbed).

The decline noted varies depending on whether cross sectional or longitudinal data are reviewed. In the Baltimore Longitudinal Study on Aging (BLSA), Lindeman, et al (1985) showed that, while there was a decrease with age in creatinine clearance, some individuals appeared to have a rapid rate of decline while 1/3 of the sample evidenced minimal decline. Further longitudinal data are needed to determine the clinical significance of these findings.

Changes in renal function do not significantly compromise the well-being of older adults in un-stressed circumstances (Castellani et al., 1998). However, vulnerability to environmental and disease challenges increases, and is enhanced by changes in homeostatic controls.


Module 6: Exploring Age-Related Body Systems Changes
6.6.4 Body Composition and…
6.6.6 Changes in Renal Homeostatic…