BMH Medical Journal

BMH Med. J. 2020; 7 (Suppl): Early Online. Geriatrics & Gerontology Initiative: International Workshop on Care of the Elderly

Introduction

Demographic transition in India is showing an increased proportion of aged population in the country. The overall life expectancy rate in India is 69.1 years, and it is 67.8 years for males and 70.5 years for females respectively. In the state of Kerala, the average life expectancy is 74.9 years with a break up of 72 years for males and 77.8 years for females. The absolute number of over 60 populations was 78 million in 2001 and is projected to be 137 million in 2021. These demographic changes influence the health, economic activity and social condition of the people.

As age advances every organ in the body undergoes structural and functional decline. It is evident when we see the wrinkled skin and flabby muscles of an elderly person. These changes are natural and compatible with comfortable living as physical and intellectual activities are less in such advanced age. Groundwork of whether a person will age well, or age poorly, begins early in life. By the time we are in our second or third decade, biological aging and chronological aging do not proceed in parallel steps [1]. Some biologic measures are more predictive of whether an individual will have a life of relatively good health, or develop chronic diseases, and die early.

Pulmonary disease has significant consequences for the aging population. Changes in the respiratory system are also natural, as our lungs enter their "golden years". However, these changes should be gradual and subtle. The normal ageing process brings about changes to the respiratory system which mean older people are at increased risk of respiratory compromise (Box-1). Our lungs mature by the time we are about 20-25 years old. After about the age of 35, it is normal for the lung function to decline gradually as age advances. Forced vital capacity (air that is expelled after a forcible exhalation) can decrease by about 200 ml per decade (20 ml/year), even for healthy non smoking person. This decline becomes 35ml/year after the age of 65 years. Forced expiratory volume in one second (FEV1) declines by 1 to 2 percent per year after about the age of 35.The respiratory system has numerous functions in addition to its central role in gaseous exchange; it has a role in regulating blood pH and maintaining mechanical and immune defenses. Lung function seems to play a significant role in healthy aging [2,3].

Case Scenario

I recollect the story of an elderly lady referred as a case of interstitial lung disease. She started experiencing shortness of breath on walking or climbing stairs for the last 3 years which is gradually progressing, affecting her house hold work. As she is living alone she has to attend to all her personal needs including cooking food. The referring physician detected fine crackles in the left lung base and advised X Ray chest which was reported as normal. Her cardiac work up was also normal. A spirometry attempted recorded poor values due to improper effort. On evaluation her respiratory system appeared normal for her age and the basal crackles detected in the left lung base is part of aging process and not due to any lung disease. This is important as the closing volume increases as age advances and left lower lobe being compressed by the left ventricle has more impact than right lower lobe. But it is difficult to convince a person who is self dependant for years and developed symptoms only recently. An HRCT thorax was advised which also reported normal with age related changes. It is important to have knowledge on lung function decline as age advances and all activities should be modified to ones comfort level. Trying to stretch it beyond a certain level to satisfy our needs make one symptomatic. Another thing which can be tried here is to build exercise tolerance. This has to be started early in life so that the impact of aging process on respiratory system will be slower.

Box-1: Case scenario of an 80 year old female with respiratory symptoms consistent with aging lungs

Structural and functional changes with aging

Chest wall is vital for optimal lung function. Changes to the spine, muscles, and ribs with aging impact normal lung function. As people normally age, narrowing of the intervertebral disc spaces causes increased kyphosis of the spine. This curvature decreases the space between the ribs and creates a smaller chest cavity [4]. After age 40, the kyphosis angle begins to increase more rapidly in women than men, from a mean of 43° in women aged 55–60 years, to a mean of 52° in women 76–80 years of age [5]. It is reported that with increasing vertebral angle there is a significant decline in the forced expiratory volume in 1 second (FEV1) and vital capacity (VC). The angle of the muscle fibers in relation to the ribs may also affect the efficiency and decrease the movement of the lower ribs during inspiration [6]. These changes are structural and based on the origin and insertion of the muscles.

Aging is associated with reduced inspiratory and expiratory muscle strength. Overall muscle function in the body decreases by 2% annually as we age [7]. The most important respiratory muscle, the diaphragm, undergoes structural changes such as flattening, fibrosis and regional weakness leading to functional decline. Respiratory muscle decline can lead to an inability to ventilate in the face of increasing demands, such as that seen in respiratory disease. There is also evidence that at the cellular level, the muscles of elderly individuals have less mitochondrial adenosine triphosphate reserves to sustain a sudden increase in metabolic demand [8]. If an elderly person becomes ill with pneumonia, and therefore has increased metabolic demands for oxygen in the setting of decreased respiratory muscle strength and decreased cellular energy reserve, he or she may not be able to meet those demands. This leads to an increased risk of respiratory failure in older individuals [9].

With aging there is a decreased ability to clear mucus from the lungs. Two mechanisms primarily contribute to this decline: 1) reduced cough strength and 2) alterations in the body’s ability to clear particles in the airways. Any decrease in the strength of the respiratory muscles will greatly impact an individual’s ability to generate the force required for an effective cough [10]. Aging is associated with reduction of both inspiratory and expiratory muscle strength. There is age-related atrophy of muscle fibers, termed sarcopenia, which may also explain the reduced respiratory strength in the elderly. The decrease in muscle fiber strength can be as high as 20% by age 70 [11].

The elasticity of the lung is reduced. Elasticity is the important factor for inflation and deflation of lungs. Once it is reduced, the natural capacity to inhale and exhale effectively is affected. Along with that the alveoli are enlarged. This leads to retention of more air in the lungs. This is called senile emphysema. These changes are much more in smokers when compared to non smokers.

Physiological changes with aging

Number of alveoli, alveolar ducts, and capillary segments are stable once adulthood is reached and total lung volume remains the same [12]. There will be reduction in functional capacity of the lung. The alveolar-capillary surface area increases [13] and elasticity decreases, resulting in an increase in resting functional residual capacity and an increase in end-expiratory lung volume. In healthy older adults, these functional changes may only be felt during extreme exertion [14], but age-related changes in capacity must be accounted for when diagnosing lung disease (Box-2).

An elderly nonsmoker used to complain of exertional breathlessness. He had multiple consultations for this and is using inhaled bronchodilator on a presumptive diagnosis of COPD. Otherwise healthy person, he has no identifiable cardiovascular morbidity. Looking at his occupation which he is doing for the last 50 years, it is evident that he is overstretching his respiratory reserve at this age. He is working as electric welder and has to manage metal rods and sheets which precipitate his breathlessness. This scenario indicates that although there may be global reduction in lung function, it is slow in development and the individual can cope up with these changes by life style modification, so that there is less work load on respiratory system.

Box-2: Case scenario of a 75 old male diagnosed as COPD without any objective evidence

FVC and FEV₁, or the ratio of FEV₁/FVC, change in a linear manner with age. The reference values inferred from younger populations are inaccurate when applied to older adults and can lead to a misdiagnosis of COPD [15]. These physiologic changes to the lungs contribute to changes in lung function and susceptibility to disease (Table 1) 12, 13. Lung diseases such as COPD and pulmonary fibrosis increase with age, as does the incidence of pneumonia [16]. In some cases, such as pulmonary fibrosis, the development of disease is clearly linked to cellular senescence such as mitochondrial dysfunction [17].

Table1: Showing physiological changes in lung function due to aging

Immunological changes with aging

Lung, over the course of an average life is exposed to particulates, ozone, aerosols, infections, allergens, and pollutants. In addition to this some people are exposed to cigarette smoke, radiation, drugs and medications, mechanical injury, and exposure to industrial pollutants. Consequently, tissue repair is of paramount importance in the lungs as we age. Inappropriate or ineffective repair can lead to fibrosis, dysplasia or remodeling. Tissue repair and remodeling are orchestrated by epithelial cells, immune cells, fibroblasts, and progenitor cells, all of which undergo age-related changes that affect function. It is found out that there is basal activation of the innate immune system in aged individuals in the absence of an immunologic threat [18]. This phenomenon, referred to as “inflammatory aging”, is marked by elevated levels of tissue and circulating pro-inflammatory cytokines in aged subjects. Related to inflammatory aging is the blunted immune response, known as “immune-senescence”, following a pathogenic threat or tissue injury [18]. Multiple studies have established reduced levels of mediators such as TNF-α, IL-6, interferon-γ, nitric oxide, monocyte chemoattractant protein-1, and macrophage inflammatory protein-1α after different types of antigenic stimulation in aged animals [19]. The interplay between inflammatory aging and immune-senescence, leads to disruption in the balance of pro- and anti-inflammatory mediators in favour of a pro-inflammatory environment with advanced age, which subsequently retards an appropriate adaptive immune response. This imbalance of immune mediators, delayed immune activation, and protracted course of inflammation may result in increased morbidity and mortality in aging individuals following infection, environmental exposures, or systemic injury.

Pathological changes with aging

Chronic respiratory diseases, such as asthma, emphysema, chronic bronchitis, bronchiectasis, and interstitial lung diseases have higher mortality among people aged 65 years and older. Many respiratory diseases develop exclusively in the elderly. Similarly many diseases have poor out come in the elderly when compared to their younger counterparts. Pneumonia severity is assessed by CURB65 score. According to this score individual aged 65 or more are at risk of developing severe pneumonia. Resolution of pneumonia is delayed and mortality is very high in elderly individuals. COPD usually starts after the age of 50 years. The prevalence of COPD is two to three times higher in people over age 60. The increased burden of COPD seen in the elderly population may be due to age-associated changes in the structure and function of the lung, increasing the susceptibility to COPD. It is a progressive disease and cause significant morbidity after 65 years of age. Acute infective exacerbations, hospitalizations and ICU admissions are more in the elderly. It is reported that infective exacerbations due to fungal infections is more common in elderly COPD patients [20]. Idiopathic pulmonary fibrosis is another disease of the elderly. Due to immunological injury and repair, progressive fibrosis develops. This causes irreversible damage to the lungs leading to compromised respiratory function. Lung cancer also is frequently manifested in the elderly individuals. Due to exposure to smoke and irritants there will be dysplastic changes. Due to poor defense in the elderly, irritants are not effectively removed from the respiratory tract. This can lead to metaplastic and neoplastic changes as age advances.

Many systemic diseases of the elderly are also linked with poor respiratory function. It is well proved that development of Type-2 diabetes, a disease of the elderly, is linked to functional decline of the lungs. Individuals whose FEV₁ and FVC are at the lower end of the normal range develop many diseases of elderly such as cardiovascular disease, type 2 diabetes and cognitive decline, earlier than those with normal lung function. A chest wall change such as increased kyphosis due to spondylosis reduces respiratory compliance. Dementia and Parkinsonism are frequent causes for aspiration related lung diseases in the elderly. It is reported that low lung function is an accelerant to the aging process; and in turn can be considered as a predictor for development of any of the age-related conditions. Consistent with this statement, a study of middle-aged adults found that lower FEV₁ and FVC at baseline correlated with lower cognitive function and an increased risk of being hospitalized for dementia.

Interventions to reduce respiratory morbidity in the elderly

•    Avoid smoking: Cigarette smoking is found to be the most important risk factor for COPD, Idiopathic pulmonary fibrosis and lung cancer. Smoking also increases the chance of development of respiratory infections such as pneumonia and tuberculosis.
•    Avoid air pollution: Indoor and outdoor air pollutants can damage the lungs. Secondhand smoke, outdoor air pollution, chemicals in the home and workplace can cause or worsen lung diseases such as asthma and COPD.
•    Exercise: Regular exercise can improve the exercise tolerance and patients feel better and comfortable at that functional level.
•    Rehabilitation: Especially vocational rehabilitation is essential as age advances. It is important to understand that the decline in pulmonary function occur as age advances and the same level of work load will not be tolerated at an advanced age.
•    Weight reduction: Abdominal fat can impede the diaphragm's ability to fully expand the lungs. A combination of both healthy eating and exercise will help in maintaining the optimal weight.
•    Immunization: It is better to have prophylactic influenza and pneumococcal vaccine after the age of 65 years. This is especially important in patients suffering from COPD and other chronic lung diseases.

Conclusion

Lung health is intimately associated with good health in older adults. There are many age-associated changes in the respiratory system. An efficient respiratory system is essential for health and longevity, but age brings about changes that reduce its efficiency. As the body ages, respiratory muscles lose strength, lung tissues lose elasticity, the alveolar surface area diminishes and lung capacity is reduced. As age increases, the respiratory system is less able to expel inhaled irritants and pathogens due to a reduced cough reflex and a decline in muco-ciliary clearance. There are many complex changes in immunity with aging that increase susceptibility to infections. It is pertinent to know the changes associated with age in order to make a proper clinical diagnosis and offer treatment. Unnecessary investigation and medication may further worsen the respiratory function. Proper counseling and precautionary measures may help the patient to lead a comfortable life with an aged lung.

References

1. Belsky, D.W., Caspi, A., Houts, R. et al Quantification of biological aging in young adults. Proc Natil Acad Sci U S A. 2015; 112: E4104–E4110.

2. Beaty TH, Cohen BH, Newill C A et al. Impaired pulmonary function as a risk factor for mortality. Am J Epidemiol. 1982; 116: 102–113.

3. Beaty TH, Newill, C.A., Cohen, B.H. et al. Effects of pulmonary function on mortality. J Chron Dis. 1985; 38: 703–710.

4. Sharma G, Goodwin J. Effect of aging on respiratory system physiology and immunology. Clin Interv Aging. 2006; 1(3):253–260.

5. Ensrud KE, Black DM, Harris F, Ettinger B, Cummings SR. Correlates of kyphosis in older women. The Fracture Intervention Trial Research Group. J Am Geriatr Soc. 1997;45(6):682–687.

6. Culham EG, Jimenez HA, King CE. Thoracic kyphosis, rib mobility, and lung volumes in normal women and women with osteoporosis. Spine. 1994; 19(11):1250–1255.

7. Arora NS, Rochester DF. Effect of body weight and muscularity on human diaphragm muscle mass, thickness, and area. J Appl Physiol. 1982; 52(1):64–70.

8. Desler C, Hansen TL, Frederiksen JB, Marcker ML, Singh KK, Juel Rasmussen L. Is there a link between mitochondrial reserve respiratory capacity and aging? J Aging Res. 2012; 2012 Article ID 192503.

9. Sevransky JE, Haponik EF. Respiratory failure in elderly patients. Clin Geriatr Med. 2003; 19(1):205–224.

10. Kim J, Davenport P, Sapienza C. Effect of expiratory muscle strength training on elderly cough function. Arch Gerontol Geriatr. 2009; 48(3):361–366.

11. Tolep K, Higgins N, Muza S, Criner G, Kelsen SG. Comparison of diaphragm strength between healthy adult elderly and young men. Am J Respir Crit Care Med. 1995; 152(2):677–682.

12. Turner JM, Mead J, Wohi ME. Elasticity of human lungs in relation to age. J Appl Physiol.1968;25:664-671.

13. Weibel, E.R. and Gomez, D.M Architecture of the human lung. Use of quantitative methods establishes fundamental relations between size and number of lung structures. Science. 1962; 137: 577–585.

14. Babb TG. Ventilatory response to exercise in subjects breathing CO2 or HeO2.J Appl Physiol. 1997; 82: 746-754.

15. Garcia-Rio, F., Dorgham, A., Pino, J.M. et al Lung volume reference values for women and men 65 to 85 years of age. Am J Respir Crit Care Med. 2009; 180: 1083–1091.

16. Budinger, G.R.S., Kohanski, R.A., Gan, W. et al. The intersection of aging biology and the pathobiology of lung diseases a joint NHLBI/NIA workshop. J Gerontol A Biol Sci Med Sci. 2017; 72: 1492–1500.

17. Coghlan, M.A., Shifren, A., Huang, H.J. et al. Sequencing of idiopathic pulmonary fibrosis-related genes reveals independent single gene associations. BMJ Open Respir Res. 2014; 1: e000057.

18. Panda A, Arjona A, Sapey E, et al. Human innate immunosenescence: causes and consequences for immunity in old age. Trends Immunol. 2009;30(7):325–333.

19. Ren Z, Gay R, Thomas A, et al. Effect of age on susceptibility to Salmonella Typhimurium infection in C57BL/6 mice. J Med Microbiol. 2009; 58(Pt 12):1559–1567

20. Lashmipriya S., Ravindran Chetambath, Amitha Sunny, Sanjeev Shivashankaran, Muhammed Aslam. Aspergillus spp. infection as a cause of acute exacerbations of chronic obstructive pulmonary disease: a prospective observational study. Int J Res Med Sci. 2019 May;7(5):1604-1609.

The Aging Lung