Academic journal article Environmental Health Perspectives

House Dust Endotoxin Association with Chronic Bronchitis and Emphysema

Academic journal article Environmental Health Perspectives

House Dust Endotoxin Association with Chronic Bronchitis and Emphysema

Article excerpt

Introduction

Chronic bronchitis is a common condition that affects 10 million Americans (American Lung Association 2014; Kim et al. 2015). The condition is characterized by airway inflammation and airway remodeling and is typically defined as chronic cough with sputum for [greater than or equal to] 3 mo per year for at least two consecutive years (Kim et al. 2015). Emphysema is a complex disease defined by alveolar wall destruction leading to a loss of elastic recoil (Barnes 2000; Sciurba 2004). Both chronic bronchitis and emphysema are phenotypes of chronic obstructive pulmonary disease (COPD), which affects >15 million Americans and is the third leading cause of death in the United States and worldwide (Burney et al. 2015; Diaz-Guzman and Mannino 2014; Heron 2013).

COPD is mainly caused by cigarette smoking, but other environmental exposures are increasingly recognized as playing a role in its development (Eduard et al. 2009; To et al. 2016). Among these environmental exposures, endotoxin is of particular interest because of its known proinflammatory properties and its effects on respiratory health (Thorne et al. 2005, 2015). Endotoxin is a lipopolysaccharide from the outer membrane of Gram-negative bacteria that is ubiquitous in our environment (Thorne et al. 2009). Animal models suggest that endotoxin induces lesions of the lung that are similar to those found with COPD, and according to preclinical in vivo models, stimulus by endotoxin can be used to reproduce COPD inflammation (Brass et al. 2008; Hakansson et al. 2012; Korsgren et al. 2012).

Despite the results obtained with animal models, only a few studies have examined the association of endotoxin with COPD in humans. These studies have all included occupational exposure to high concentrations of endotoxin, but to date, there has been no study on the levels of endotoxin found in homes (Basinas et al. 2012; Eduard et al. 2009; Mehta et al. 2010). Therefore, we examined the association of house-dust endotoxin with chronic bronchitis or emphysema (CBE) suggestive of COPD in a large sample representative of the U.S. population using the National Health and Nutrition Examination Survey (NHANES). The topic is of public health interest given the ubiquity of endotoxin in our environment and the high morbidity of chronic obstructive pulmonary conditions in the United States.

Materials and Methods

Data Source and Study Design

We used data from the 2005-2006 National Health and Nutrition Examination Survey (NHANES) conducted by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC). NHANES is a continuous cross-sectional survey of the U.S. noninstitutionalized civilian population, selected using a complex multistage sampling design to derive a representative sample of the U.S. population. People below the poverty level, 12 to 19 y old, [greater than or equal to] 60 y old, pregnant women, African Americans, and Mexican Americans were oversampled in the 2005-2006 cycle to ensure adequate subgroup analyses. Of the 3,403 NHANES participants [greater than or equal to] 20 y old who had data on house dust endotoxin, 3,393 (99.7%) also had data on emphysema, chronic bronchitis, or both and were included in our study.

NHANES protocols were approved by the Institutional Review Boards of the NCHS and the CDC, and informed consent was obtained from all participants. Details of the IRB approval are available here: http://www.cdc.gov/nchs/nhanes/irba98.htm. Details on NHANES procedures and methods are available here: https://wwwn.cdc.gov/nchs/nhanes/continuousnhanes/manuals. aspx?BeginYear=2005.

Endotoxin analysis

Combined bed and bedroom floor dust samples were collected at each participant's home using a vacuum cleaner fitted with a Mitest[TM] Dust Collector (Indoor Biotechnologies, Inc). A surface area of 0.84 [m.sup.2] on beds and the adjacent floors were each vacuumed for 2 min. …

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