Aging and pulmonary function
The aging process is associated with degenerative changes. These are associated with a decline in lung function. In healthy subjects this does not limit daily activities thanks to the large reserve capacity of the lung.
Old age may be associated with severe osteoporosis, particularly in women. Skeletal decalcification leads to gradual shortening of the trunk by several centimeters, and thus to a shorter standing height and smaller lung (ref. 1). This implies interaction between age and standing height.
Successive birth cohorts become progressively taller. Studies of Japanese children, and of American and Norwegian conscripts showed (ref. 2) that the increased standing height is almost entirely accounted for by longer legs. The secular increase in standing height occurs in the first 2 years of life (Cole).
The above findings are not taken into account in published regression equations. In practice, therefore, the decline in ventilatory function after age 25 yr is attributed solely to age-related effects on the lung. In Caucasian communities this may be correct, as a recent study did not reveal a secular trend in pulmonary function in the period 1980-2010 (Quanjer).
|Ref. 1 - Osteoporosis and lung function in women|
|Kyphosis and thoracic compression fractures in postmenopausal women lead to a lower vital capacity:|
|1||Leech JA, Dulberg C, Kellie S, Pattee L, Gay J. Relationship of lung function to severity of osteoporosis in women. Am Rev Respir Dis 1990; 141: 68-71.|
|Ref. 2 - Secular increase in standing height|
|1||Tanner JM, Hayashi T, Preece MA, Cameron N. Increase in length of leg relative to trunk in Japanese children and adults from 1957 to 1977: comparison with British and with Japanese Americans. Ann Hum Biol 1982; 9: 411-423.|
|2||Quanjer PH, Stocks J, Cole TJ, Hall GL, Stanojevic S. Influence of secular trends and sample size on reference equations for lung function tests, Eur Respir J 2011; 37: 658–664.|
|3||Cole TJ. The secular trend in human physical growth: a biological view. Econ Hum Biol 2003; 1: 161–168..|