Excessive longitudinal FEV1 decline and risks to future health: a case-control study

A prognostic model of excessive lung function decline among Québec apprentices: a cohort exposed to occupational sensitizing agents

BACKGROUND Forced expiratory volume in 1 second (FEV1) decline as a predictor of lung-related health problems is widely observed, but not fully investigated. This study aimed to develop models to predict FEV1 decline among apprentices exposed to sensitizing agents. METHODS Of 692 apprentices recruited and followed in 3.6–17.3 years, 292 were exposed to low-molecular weight agents. The analysis was restricted to 357 apprentices with complete lung function assessment at the end of their training with a minimum of 5-year follow-up. According to the American Thoracic Society guideline, a mean FEV₁ decline >60 ml/year was defined as “accelerated.” Descriptive statistics and Cox regression analysis were utilized to determine its predictors. To develop the prognostic models, we used a logistic regression analysis adjusted for the follow-up duration. The accuracy of the models was quantified using calibration and discrimination measures. RESULTS Of 357 subjects, 62 (17.4%) had an excessive FEV1 decline post-apprenticeship. The questionnaire model (model 1), which included male sex, wheezing, and exposure to isocyanate or animal allergens during the apprenticeship, showed a reasonable discriminative ability (area under the receiver operating characteristics curve [AUC] of 0.67, 95% CI = 0.59–0.75). Adding the percent-predicted FEV₁ value at the end of apprenticeship significantly increased the discriminative ability of the model (model 4) (AUC = 0.762, 95% CI = 0.694–0.829) with a good calibration and reasonable internal validity. CONCLUSIONS We developed a model for accelerated lung function decline with a good accuracy and internal validity. However, external validation of the model is necessary.

Increased Airway Wall Thickness is Associated with Adverse Longitudinal First-Second Forced Expiratory Volume Trajectories of Former World Trade Center workers

RATIONALE

Occupational exposures at the WTC site after September 11, 2001 have been associated with several presumably inflammatory lower airway diseases. In this study, we describe the trajectories of expiratory air flow decline, identify subgroups with adverse progression, and investigate the association of a quantitative computed tomography (QCT) imaging measurement of airway wall thickness, and other risk factors for adverse progression.

METHODS

We examined the trajectories of expiratory air flow decline in a group of 799 former WTC workers and volunteers with QCT-measured (with two independent systems) wall area percent (WAP) and at least 3 periodic spirometries. We calculated individual regression lines for first-second forced expiratory volume (FEV₁), identified subjects with rapidly declining and increasing ("gainers"), and compared them to subjects with normal and "stable" FEV₁ decline. We used multivariate logistic regression to model decliner vs. stable trajectories.

RESULTS

The mean longitudinal FEV₁slopes for the entire study population, and its stable, decliner, and gainer subgroups were, respectively, - 35.8, - 8, - 157.6, and + 173.62 ml/year. WAP was associated with "decliner" status (OR_adj 1.08, 95% CI 1.02, 1.14, per 5% increment) compared to stable. Age, weight gain, baseline FEV₁ percent predicted, bronchodilator response, and pre-WTC occupational exposures were also significantly associated with accelerated FEV₁ decline. Analyses of gainers vs. stable subgroup showed WAP as a significant predictor in unadjusted but not consistently in adjusted analyses.

CONCLUSIONS

The apparent normal age-related rate of FEV₁ decline results from averaging widely divergent trajectories. WAP is significantly associated with accelerated air flow decline in WTC workers.

Official American Thoracic Society technical standards: spirometry in the occupational setting

PURPOSE

This document addresses aspects of the performance and interpretation of spirometry that are particularly important in the workplace, where inhalation exposures can affect lung function and cause or exacerbate lung diseases, such as asthma, chronic obstructive pulmonary disease, or fibrosis.

METHODS

Issues that previous American Thoracic Society spirometry statements did not adequately address with respect to the workplace were identified for systematic review. Medline 1950-2012 and Embase 1980-2012 were searched for evidence related to the following: training for spirometry technicians; testing posture; appropriate reference values to use for Asians in North America; and interpretative strategies for analyzing longitudinal change in lung function. The evidence was reviewed and technical recommendations were developed.

RESULTS

Spirometry performed in the work setting should be part of a comprehensive workplace respiratory health program. Effective technician training and feedback can improve the quality of spirometry testing. Posture-related changes in FEV1 and FVC, although small, may impact interpretation, so testing posture should be kept consistent and documented on repeat testing. Until North American Asian-specific equations are developed, applying a correction factor of 0.88 to white reference values is considered reasonable when testing Asian American individuals in North America. Current spirometry should be compared with previous tests. Excessive loss in FEV1 over time should be evaluated using either a percentage decline (15% plus loss expected due to aging) or one of the other approaches discussed, taking into consideration testing variability, worker exposures, symptoms, and other clinical information.

CONCLUSIONS

Important aspects of workplace spirometry are discussed and recommendations are provided for the performance and interpretation of workplace spirometry.