ORIGINAL ARTICLE

Decline in lung function and mortality: implications for medical monitoring

Kanta Sircar, Eva Hnizdo, Edward Petsonk, Michael Attfield

National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA

Correspondence to:
Dr K Sircar
National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA; KSircar{at}cdc.gov

Aim: To investigate the risk of death associated with selected cut-off points for rate of decline of forced expiratory volume in one second (FEV₁).

Methods: Mortality rates of a cohort of 1730 coal miners who had performed two pulmonary function tests 12.8 years apart were followed up for an additional 12 years. Based on previous studies, cut-off points for FEV₁ rate of decline (ml/year) were selected as 30, 60 and 90 ml/year. Cox proportional hazard regression was used to estimate multivariate risk ratio of death in each category.

Results: The risk ratios (compared to "below 30 ml/year") were 1.39 (95% CI 0.99 to 1.97) in the "60 to less than 90 ml/year" category and 1.90 (95% CI 1.32 to 2.76) in the "90 ml/year and above" category. Rates of decline above 90 ml/year were consistently related to excess mortality. In non-smokers and those with neither restrictive nor obstructive patterns at the first survey, rates of decline above 60 ml/year were significantly associated with increased mortality.

Conclusions: Risk of death increases in individuals with rates of decline above about 60 ml/year and is statistically significant with declines of 90 ml/year or more. These results should be useful to healthcare providers in assessing lung function declines observed in individuals.

Abbreviations: ATS, American Thoracic Society; BMI, body mass index; FEV₁, forced expiratory volume in one second; ICD-9, International Classification of Diseases Ninth Revision; NSCWP, National Study of Coal Workers’ Pneumoconiosis; PFT, pulmonary function test

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