The Relationship Between Lung Capacity and Ageing

Author: Rohan Smith | Functional Medicine Practitioner | Adelaide, SA

What Is Lung Capacity and Why It Changes With Age

Total lung capacity in healthy adults averages approximately 6 litres, but this value is influenced by age, sex, height, and ethnicity. Clinically, respiratory function includes measures such as vital capacity, forced expiratory volume (FEV1), and total lung capacity, which are commonly assessed through spirometry as standardised by the American Thoracic Society (ATS) and European Respiratory Society (ERS).

Ageing is associated with several physiological changes that influence these measures. Janssens and colleagues, writing in the European Respiratory Journal (1999), described reduced elastic recoil, a stiffer chest wall and weaker respiratory muscles with age. The table below sets out these and related changes:

While these changes do not necessarily indicate disease, they reduce respiratory reserve, which can become clinically relevant during physical exertion, illness, or periods of physiological stress. Skloot (2017), writing in Clinics in Geriatric Medicine, noted that residual volume may increase by up to 50% between ages 20 and 70 due to these structural changes.

Assessing Lung Function in Clinical Practice

Spirometry is the most common lung function test, and the ATS/ERS technical statement (2019) sets the standards for how it is performed. It evaluates airflow and lung volumes, including FEV1, forced vital capacity (FVC), and the FEV1/FVC ratio. These measurements provide insight into ventilatory efficiency and airway function.

Additional assessments may include the six-minute walk test (6MWT), as described by Enright in Respiratory Care (2003), which evaluates functional exercise capacity and correlates with respiratory reserve. In functional medicine settings, spirometry findings are often interpreted alongside exercise tolerance, symptom patterns, body composition metrics, and broader metabolic markers such as inflammatory cytokines and oxidative stress biomarkers to assess overall respiratory reserve.

Functional and Lifestyle Factors That Influence Respiratory Ageing

Modifiable factors may influence how quickly lung function declines with age. In a Copenhagen cohort of 6,790 people, Garcia-Aymerich and colleagues (2007) linked moderate to high levels of regular physical activity with slower lung function decline among smokers.

Physical Activity

Regular aerobic exercise is associated with improved ventilatory efficiency and preservation of respiratory muscle strength. A Cochrane review by McCarthy and colleagues (2015) found that pulmonary rehabilitation, which is built around exercise training, improved exercise capacity and eased breathlessness in people with COPD. Increased oxygen demand during physical activity promotes deeper breathing patterns, which may help maintain lung compliance and functional capacity over time.

Breathing Mechanics

Inspiratory muscle training, one form of respiratory muscle training, improved inspiratory muscle strength in healthy older adults in a meta-analysis by Manifield and colleagues in Age and Ageing (2021), although it showed no clear effect on functional capacity. Breathing retraining techniques such as diaphragmatic breathing and paced nasal breathing may improve ventilation efficiency and reduce reliance on accessory muscles, particularly in sedentary or chronically stressed individuals.

Smoking Status

Tobacco exposure accelerates age-related declines in FEV1 and lung elasticity. Fletcher and Peto’s landmark 1977 study in the British Medical Journal established that smoking cessation is consistently associated with a slower rate of lung function decline compared with continued smoking. Salvi and Barnes (2009) further demonstrated in The Lancet that non-smoking risk factors including occupational exposures and biomass fuel exposure also contribute to chronic airflow obstruction.

Body Composition

Excess adiposity, particularly central adiposity, can restrict diaphragmatic excursion and reduce functional residual capacity (FRC) and expiratory reserve volume (ERV). Weight optimisation may therefore improve respiratory mechanics and perceived breathlessness. Jones and Nzekwu (2006) reported that functional residual capacity and expiratory reserve volume fell as body mass index rose, with the steepest changes in the overweight and mildly obese range.

Hydration and Mucosal Health

Adequate hydration supports mucociliary clearance and airway moisture, which may influence breathing comfort and airway defence mechanisms. Maintaining healthy mucosal surfaces is associated with improved innate immune function in the respiratory tract.

When to Consider Clinical Assessment

Early detection of accelerated lung function decline can inform targeted intervention strategies. Assessment of lung function may be appropriate if an individual experiences:

• Shortness of breath disproportionate to activity level
• Reduced exercise tolerance
• Persistent fatigue not explained by cardiovascular or metabolic causes
• A history of smoking, occupational exposure, or recurrent respiratory infections

In clinical practice, reduced respiratory reserve may also contribute to symptoms seen in individuals with chronic fatigue, where exertional intolerance and delayed recovery are common. MacNee (2009), writing in Biochemical Society Transactions, described evidence linking accelerated lung ageing with chronic obstructive pulmonary disease (COPD), which is one reason clinical assessment is worthwhile when these symptoms persist.

Next Steps

1. Assess your baseline: If you experience unexplained breathlessness or reduced exercise tolerance, consider spirometry testing to evaluate your current lung function and distinguish normal ageing from pathological impairment.
2. Prioritise aerobic exercise: Regular cardiovascular activity promotes deeper breathing patterns and helps maintain respiratory muscle strength and lung compliance over time.
3. Explore breathing retraining: Techniques such as diaphragmatic breathing and paced nasal breathing can improve ventilation efficiency, particularly if you are sedentary or chronically stressed.

Breathe Easier, Age Better

If you are experiencing unexplained breathlessness, reduced exercise tolerance, or persistent fatigue, a functional medicine assessment can help identify whether respiratory decline, metabolic dysfunction, or other systemic contributors are at play. At Elemental Health and Nutrition, we take a systems-based approach to respiratory and metabolic health, helping you preserve function and resilience as you age.

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Declining respiratory efficiency accelerates the fatigue burden already seen in hormonal and stress-related conditions, where cortisol dysregulation further impairs tissue oxygenation and recovery capacity.