Aging of the Respiratory System: Impact on Pulmonary
Function Tests and Adaptation to Exertion
Jean-Paul Janssens, MD
Outpatient Section of the Division of Pulmonary Diseases, Geneva University Hospital, 1211 Geneva 14, Switzerland
Life expectancy has risen sharply during the past
century and is expected to continue to rise in virtually
all populations throughout the world. In the United
States population, life expectancy has risen from
47 years in 1900 to 77 in 2001 (74.4 for the male and
79.8 for the female population) . The proportion of
the population over 65 years of age currently is more
than 15% in most developed countries and is ex-
pected to reach 20% by the year 2020. Healthy life
expectancy, at the age of 60, is at present 15.3 years
for the male population and 17.9 years for the female
population . These demographic changes have a
major impact on health care, financially and clini-
cally. Awareness of the basic changes in respiratory
physiology associated with aging and their clinical
implication is important for clinicians. Indeed, age-
associated alterations of the respiratory system tend
to diminish subjects’ reserve in cases of common
clinical diseases, such as lower respiratory tract in-
fection or heart failure [3,4].
This review explores age-related physiologic
changes in the respiratory system and their conse-
quences in respiratory mechanics, gas exchange, and
respiratory adaptation to exertion.
Structural changes in the respiratory system
related to aging
Most of the age-related functional changes in the
respiratory system result from three physiologic
events: progressive decrease in compliance of the
chest wall, in static elastic recoil of the lung (Fig. 1),
and in strength of respiratory muscles.
Age-associated changes in the chest wall
Estenne and colleagues measured age-related
changes in chest wall compliance in 50 healthy
subjects ages 24 to 75: aging was associated with a
significant decrease (?31%) in chest wall compli-
ance, involving rib cage (upper thorax) compliance
and compliance of the diaphragm-abdomen compart-
ment (lower thorax) . Calcifications of the costal
cartilages and chondrosternal junctions and degenera-
tive joint disease of the dorsal spine are common
radiologic observations in older subjects and contrib-
ute to chest wall stiffening . Changes in the shape
of the thorax modify chest wall mechanics; age-
related osteoporosis results in partial (wedge) or
complete (crush) vertebral fractures, leading to
increased dorsal kyphosis and anteroposteriordi-
ameter (barrel chest). Indeed, prevalence of vertebral
fractures in the elderly population is high and
increases with age; in Europe, in female subjects
over 60, the prevalence of vertebral fractures is
16.8% in the 60 to 64 age group, increasing to 34.8%
in the 75 to 79 age group . Men also show an
increase in vertebral fractures with age, but rates are
approximately half those of the female population
. A study of 100 chest radiographs of subjects ages
75 to 93 years, without cardiac or pulmonary dis-
orders, illustrates the frequency of dorsal kyphosis
in this age group: 25% had severe kyphosis as a
consequence of vertebral wedge or crush fractures
(>50?), 43% had moderate kyphosis (35?–50?), and
only 23% had a normal curvature of the spine .
0272-5231/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved.
E-mail address: Jean-Paul.Janssens@hcuge.ch
Clin Chest Med 26 (2005) 469 – 484
Respiratory muscle function
Respiratory muscle performance is impaired con-
comitantly by the age-related geometric modi-
fications of the rib cage, decreased chest-wall
compliance, and increase in functional residual
capacity (FRC) resulting from decreased elastic recoil
of the lung (Fig. 2) . The kyphotic curvature of the
spine and the anteroposterior diameter of the chest
increase with aging, thereby decreasing the curvature
of the diaphragm and thus its force-generating
capacity . Changes in chest wall compliance lead
to a greater contribution to breathing from the dia-
phragm and abdominal muscles and a lesser contri-
bution from thoracic muscles. The age-related
reduction in chest-wall compliance is somewhat
greater than the increase in lung compliance; thus,
compliance of the respiratory system is 20% less in a
60-year-old subject compared with a 20-year-old (see
Fig. 1) . As such, during normal resting tidal
breathing, the increase in breathing-related energy
expenditure (elastic work) in a 60-year-old man is
estimated at 20% compared with that of a 20-year-
old, placing an additional burden on the respiratory
Respiratory muscle strength decreases with age
(Table 1). Polkey and colleagues report a significant,
although modest, decrease in the strength of the
diaphragm in elderly subjects (n=15; mean age 73,
range 67–81 years) compared with a younger control
group (n=15; mean age 29, range 21–40 years):
?13% for transdiaphragmatic pressure during a
maximal sniff (sniff transdiaphragmatic pressure
[Pdi]: 119 versus 136 cm H2O) and ?23% during cer-
vical magnetic stimulation (twitch Pdi: 26.8 versus
35.2 cm H2O) . There was, however, a consid-
erable overlap between groups, and the magnitude
of the difference in this study was relatively small.
0 102030 40 -10
Pressure (cm H2O)
0 10 20 30
Pressure (cm H2O)
Fig. 1. Static pressure-volume curves showing changes in the compliance of the chest wall, the lung, and the respiratory system
between an ‘‘ideal’’ 20-year-old (A) and a 60-year-old subject (B). Note increase in RV and FRC and decrease in slope of
pressure-volume curve for the respiratory system (rs) in the older subject, illustrating decreased compliance of the respiratory
system. (Data from Turner J, Mead J, Wohl M. Elasticity of human lungs in relation to age. J Appl Physiol 1968;25:664–71.)
Similarly, Tolep and coworkers report maximal
Pdi values in healthy elderly subjects (n=10; ages
65–75, 128 ± 9 cm H2O), which were 25% lower
than values obtained in young adults (n=9; ages
19–28, 171 ± 8 cm H2O) . Although one cross-
sectional study fails to demonstrate any relationship
between age and maximal static respiratory pressures
in 104 subjects over 55 , larger studies—also
based on noninvasive measurements (maximal inspir-
atory and expiratory pressures [MIP and MEP] at the
mouth and sniff nasal inspiratory pressure [SNIP])—
document an age-related decrease in respiratory
muscle performance [13–16].
Respiratory muscle strength is related to nutri-
tional status, often deficient in the elderly. Enright
and colleagues demonstrate significant correlations
between MIP or MEP pressures and lean body mass
(measured by bioelectric impedance), body weight, or
body mass index . Arora and Rochester show the
deleterious impact of undernourishment on respira-
tory muscle strength or maximal voluntary ventila-
tion: the decrease in respiratory muscle strength and
maximal voluntary ventilation was highly significant
in undernourished subjects (71 ± 6% of ideal body
weight) compared with control subjects (104 ± 10%
of ideal body weight) . Necropsy studies confirm
the correlation between body weight and diaphragm
muscle mass further .
Age-associated alterations in skeletal muscles also
affect respiratory muscle function . MIP and
MEP in elderly subjects are correlated strongly and
independently with peripheral muscle strength (hand-
grip) . Peripheral muscle strength declines with
aging. Bassey and Harries report a 2% annual
decrease in handgrip strength in 620 healthy subjects
over age 65 . Decrease in muscle strength results
from a decrease in cross-sectional muscle fiber area
(process referred to as sarcopenia), a decrease in the
number of muscle fibers (especially type II fast-
twitch fibers and motor units), alterations in neuro-
muscular junctions, and loss of peripheral motor
neurons with selective denervation of type II muscle
fibers [21–26]. Other proposed mechanisms of age-
related muscular dysfunction include impairment of
the sarcoplasmic reticulum Ca++pump resulting from
uncoupling of ATP hydrolysis from Ca++transport
(which may reduce maximal shortening velocity and
relaxation), loss of muscle proteins resulting from
decreased synthesis (ie, decreased ‘‘repair’’ ability
and protein turnover), and a decline in mitochondrial
oxidative capacity [27–31].
Respiratory muscle function also is dependent on
energy availability (ie, blood flow, oxygen content,
and carbohydrate or lipid levels) . Decreased
respiratory muscle strength is described in patients
who have chronic heart failure (CHF). Mancini and
colleagues show that CHF has a highly significant
impact on respiratory muscle strength and on the
tension-time index . The tension-time index de-
scribes the relationship between force of contraction
(Pdi/Pdimax) and duration of contraction (ratio of
inspiratory time to total respiratory cycle duration
[TI/TTOT]) and is related inversely to respiratory
muscle endurance. In elderly subjects who have heart
Maximal inspiratory and expiratory pressures measured at
the mouth in older subjects, by age group and sex
Age group (y)
MIP (cm H2O)
MEP (cm H2O)
Data from Enright PL, Kronmal RA, Manolio TA, et al.
Respiratory muscle strength in the elderly: correlates and
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Fig. 2. Progressive and linear increase in RVand FRC
between the ages of 20 and 60 years. Gray zones represent
± 1 SD. (Data from Turner J, Mead J, Wohl M. Elasticity of
human lungs in relation to age. J Appl Physiol 1968;25:
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