Lung function over the life cycle
Forced vital capacity as a predictor of longevity.
PEOPLE have often discussed the virtues of lung function in the prediction of survival at all ages.
In infants born extremely prematurely, difficult-to-control asthma, smoking-related lung disease and chronic obstructive pulmonary disease (COPD), much emphasis has been placed on markers of airway obstruction obtained through spirometry.
Of primary importance are measures of expiratory airflow, such as the forced expiratory volume in the first second of expiration (FEV1).
Moreover, there are many studies which have shown relationships between increased cardiovascular risk and a lower FEV1.
Some recent epidemiological work has cast some doubt on this for otherwise healthy people with no history or symptoms of lung disease, which has suggested that it is the forced vital capacity (FVC) that may independently predict a person’s longevity.
Data was gathered from the limited access data set of the Atherosclerosis Risk in Communities (ARIC) study that recruited participants from four regions of the US in the age group 45–64 years commencing in 1986.
A subset of 7489 people with usable spirometry who had no history of respiratory disease had their lung function analysed in relation to their survival.
The authors found no association between FEV1 or FEV1/FVC ratio, as markers of airway obstruction and survival; however, a relationship between FVC and survival was found.
In particular, there was a higher likelihood of survival with a larger FVC, with a hazard ratio of death of 0.90 for men and 0.82 for women.
This association was not explained by age, anthropometry, smoking, income, occupation or blood pressure.
The implications of this are significant in terms of the tracking of lung function from birth through the course of life.
It is known that lung function peaks in the third decade, but what is being increasingly shown is that lung function tracks from childhood to its peak and declines, at least in terms of FEV1, by about 1% per year.
This has generally been used when estimating the decline in lung function for people with a risk of obstructive lung disease, such as COPD or respiratory failure with cystic fibrosis.
The presence of a predictable association between FVC in people without respiratory disease, suggests that the emphasis on FEV1 may be excessive, as FEV1 is proportionate to the FVC, and so the decline in FVC may be more important.
FVC in later life, type 2 diabetes, cardiovascular risk and conditions associated with low-grade inflammation, e.g. metabolic syndrome, are all associated with poor fetal growth.
Consequently, this raises the importance of antenatal and early childhood factors as antecedents of long-term survival.
Factors such as genetics as well as environmental antenatal factors, including poor nutrition, maternal smoking and alcohol consumption, may have long-term implications for longevity. Importantly, the Barker hypothesis is consistent with both a reduction in FVC and FEV1 in adulthood.
Postnatally, factors such as recurrent lower respiratory tract infections, poor air quality from nanoparticle inhalation from indoor heaters and cooking facilities, as well as road traffic pollution exposure, all contribute to compromised respiratory function and potentially to lower lung function.
Therefore, the importance of early childhood respiratory wellbeing has significant lifelong implications, and this point should not be lost on those of us caring for children.
Clinical Professor Dominic Fitzgerald MBBS, PhD, FRACP
Paediatric respiratory and sleep physician at The Children’s Hospital at Westmead, NSW.
Burney PGJ, Hooper R. Forced vital capacity, airways obstruction and survival in a general population form the USA. Thorax 2011; 66: 49-54.
Tags: , Child health