Semin Respir Crit Care Med 2010; 31(5): 519-520
DOI: 10.1055/s-0030-1265892
PREFACE

© Thieme Medical Publishers

Impact of Aging on the Lung

Keith C. Meyer1
  • 1Department of Medicine, Section of Allergy, Pulmonary, and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
Further Information

Publication History

Publication Date:
12 October 2010 (online)

Human life expectancy at birth has doubled over just the past 200 years. The previous doubling of the human life span is estimated to have occurred over ~300,000 generations since humans and chimpanzees diverged from a common great ape ancestor on the African continent. The subsequent doubling of life span from 1800 to the present has been attributed to improved, safer environments and improved nutrition plus, more recently, the advent of health-preserving behavior modification and medicosurgical therapies for a variety of human diseases. This marked advance in life span and the burgeoning human population to which it has led are now stressing the global environment and are projected to lead to considerable atmospheric warming with potentially disastrous consequences. The global human population is projected to be 9.1 billion in 2050, and feeding the world's population will present an ever greater challenge as the loss of biodiversity and consequent species extinction accelerate.

According to US census data and projections, the fastest-growing segment of the US population is > 65 years old. As the demographics in the United States change, there are projections for a doubling of the elderly population (defined as > 65 years of age) within the next 20 to 30 years. As the elderly population burgeons in the United States and elsewhere, scientific investigations that seek to unlock the secrets of the aging process have also accelerated. Studies of organisms such as yeast, Caenorhabditis elegans, and the long-lived mole rat have identified numerous genes that are key in modulating stress responses and metabolic functions that can have a profound impact on susceptibility to aging. Interestingly, gene expression has been shown to become more variable with advancing age, reflecting epigenetic influences on gene expression. A decreasing ability to prevent oxidative damage to DNA, progressively dysfunctional autophagy that leads to inappropriate and early cell death, and a decline in the ability to downregulate inflammation all likely contribute to the decline in organ system function that characterizes aging. However, modulation of certain genes, such as those that encode proteins that make up the insulin-like growth factor (IGF-1) signaling pathway, can have a profound effect on aging in animal models.

Lung structure and function change considerably with advancing age. It has been estimated that function of the human lung would decline to the point of being unable to support the life of the individual if humans lived to an age of 130 to 140 years. This aging can be greatly accelerated by exposure to tobacco smoke. There is increasing evidence that immunologic changes and immune dysregulation may contribute to senescent changes in the aged human lung and predispose the elderly to the development of lung infection or malignancy. Telomere shortening and telomerase deficiency have been implicated in the development of both chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF), and a decline in gene expression of various antiaging molecules may contribute to senescent changes in the normal human lung of older individuals.

This issue of the journal focuses on changes in lung function that occur as a consequence of the aging process and examines respiratory disorders that are linked to advanced age. Dr. Miller reviews changes in lung structure and physiological function that occur with advancing age and comments on difficulties in interpreting pulmonary function test results in the elderly. Drs. Taylor and Johnson describe the remodeling changes that occur in the pulmonary circulation with advancing age and the consequences of these changes plus the loss of lung elastic recoil for exercise responses in elderly individuals.

The senescent lung is increasingly prone to injury and infection. Dr. Wang and colleagues describe the interface of the lung with the external environment and examine the susceptibility of the lung to injury from environmental exposures. They identify changes in protective mechanisms that occur with advanced age and explain how these changes increase the risk of lung injury and inflammation in the elderly. Dr. Jadcherla and colleagues review and describe the development of the upper airway and upper esophageal reflexes that protect against aspiration and identify changes with advanced age that can lead to an increased risk of aspiration events. Dr. Meyer describes changes in immune responses with advanced age and how these may predispose elderly individuals to lung inflammation as well as susceptibility to respiratory infections. In addition to bacterial pulmonary infections and community-acquired pneumonia, tuberculosis continues to pose a significant health problem. Drs. Guzmán and Vargas review the ongoing, worldwide battle against tuberculosis, which is especially prevalent in the developing world and disproportionately affects the elderly.

Aging is associated with the onset of airway and parenchymal disorders that range from asthma to pulmonary fibrosis. Dr. Mathur reviews changes in allergic responses that have been associated with advanced age and how immunosenescence may predispose elderly individuals to develop asthma. Dr. Mathur also comments on the treatment of asthma in elderly patients. Dr. Hanania and colleagues focus their discussion on COPD in the elderly. COPD is highly prevalent in the elderly population, and it is frequently unrecognized. Dr. Hanania et al discuss management strategies for the elderly patient with COPD that can maximize compliance and minimize pharmacological complications. Interstitial lung diseases associated with rheumatoid arthritis and idiopathic pulmonary fibrosis are pulmonary parenchymal diseases that are strongly associated with advanced age. Dr. Selman and colleagues examine genetic and cellular changes that increase the risk of developing fibrotic lung disorders with advanced age.

It has been increasingly recognized that sleep becomes progressively altered as a consequence of aging. Dr. Edwards and colleagues review the physiological changes in various aspects of sleep that occur in the elderly and provide a comprehensive description of sleep-disordered breathing problems that can affect aged individuals. Lastly, Dr. Muir and colleagues discuss respiratory failure in the elderly and present strategies that can be used to manage ventilatory compromise noninvasively and, if appropriate, in the outpatient setting.

As interest in the biological basis for the aging process increases and key changes in gene expression that modulate aging are identified, strategies to preserve lung function and exercise capacity in advanced age may be forthcoming. I thank the contributors to this issue for taking the time to review the literature on their respective topics and provide their perspective on salient aspects of aging and lung function. I greatly appreciate their efforts, and I also thank Anita Kaufman of Thieme Medical Publishers and Griselda Maldonado for their help in pulling all the manuscripts together for this issue of the journal. Finally, I thank Dr. Joseph Lynch for his help and support in preparing this issue and bringing this topic to the attention of readers of Seminars in Respiratory and Critical Care Medicine.

Keith C MeyerM.D. M.S. 

Department of Medicine, Section of Allergy, Pulmonary, and Critical Care Medicine; University of Wisconsin School of Medicine and Public Health

K4/910 CSC 600 Highland Ave., Madison, WI 53792

Email: kcm@medicine.wisc.edu

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