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Secondhand Smoke and Nontuberculous Mycobacterial Infection

Institution: University of California, San Diego
Investigator(s): Phung Lam, Ph.D.
Award Cycle: 2007 (Cycle 16) Grant #: 16KT-0029 Award: $270,000
Subject Area: Epidemiology
Award Type: New Investigator Awards

Initial Award Abstract
Nontuberculous mycobacteria (NTM) are bacteria that are commonly found in water and wet soil. As a coastal state, California may have greater NTM in the environment than non-coastal states. In recent years, lung disease caused by NTM appears to be increasing worldwide. Little is known about the reasons for development of this disease. Firsthand smoking may contribute to NTM disease by causing other lung diseases. However, a large group of individuals with NTM disease consists mainly of elderly women who never smoked. Secondhand smoke (SHS) may weaken the lung’s defense against NTM or cause lung damage to facilitate growth of NTM in the lungs. This study is the first to test whether SHS plays a role in the occurrence of NTM infection, disease, and worsening of infection over time. It is also the first study to explore the combined effects of contact with both SHS and NTM in the environment. To answer these questions, we will study patients with and without NTM infection and compare their history of SHS and NTM contact.

Study subjects are patients, seen at the UCSD Medical Center, who are from diverse racial backgrounds and are not infected with HIV (human immunodeficiency virus). We will first select patients who are infected with NTM using laboratory records from 2000 to 2004. We will also select a comparison group consisting of patients who are not infected with NTM. Their past medical records will be reviewed, and they will be invited to participate in the current study between January 2008 and December 2009. About 368 patients are expected to participate; about 220 participants are expected to be nonsmokers. Study participants will complete a survey, receive a physical exam, receive an image scan of their chest, cough up mucus from the lungs, and donate blood. The survey will include questions about contact with SHS in different places (home, work, and social settings), by timing, and by amount. The survey will also include questions about contact with NTM in different places and by activities (showering, swimming, hot tub use, gardening, and contact with pets). Blood samples will be tested for byproducts of tobacco smoke and NTM.

If NTM grows in the laboratory from the collected mucus samples, we say that the subject has current NTM infection. NTM disease is diagnosed only if NTM can grow from mucus, if patients have symptoms, and if the chest image shows abnormalities. Assessment of worsening NTM-related lung conditions will be determined by a pulmonologist and a radiologist who evaluate these three features between past health reviews and current health exams. Data analysis will determine the relation between SHS and NTM infection and disease, by taking all of the relevant patient information into account including their level of contact with NTM in the environment.

The results of this work may affect women, older people, and the study of environmental exposures. NTM disease can be a life-long disease that is difficult and expensive to treat and causes great suffering or death. If tobacco smoke contributes to NTM infection and disease, reducing contact with tobacco smoke may prevent the infection or limit its effects.