The natural history of respiratory system function

Lung growth starts in the first year of life. Between 20-30 years of age, man achieves the maximum FEV1. Some years later, maximum FVC is achieved. After the phase of a dynamic increase, lung function stabilizes for a while. Thereafter, it starts declining slowly in some individuals or increasing in others. The third and last phase of lung function changes during a lifetime begins between 40-45 years of life. The FEV1 and some years later also FVC diminish with a varied speed during this period. Changes in FEV1 and FVC in the third phase are slower at the beginning and accelerate in the six or seventh decade of life. There are some differences between males and females concerning the lung function profile. Female lung function starts decreasing earlier than that in male individuals. There are also pronounced interindividual differences in lung function among individuals of a similar age and body height.