Growing health threat may have genetic component
by Jennifer Holder, TC Daily Planet
Mary Manning, a 66-year-old St. Paul African American resident, has Chronic Obstructive Pulmonary Disease (COPD) – the fourth leading cause of death in the U.S. and the only cause of death on the rise. COPD is a slowly progressive disease of the airways that is characterized by a gradual loss of lung function. The term COPD includes chronic bronchitis, chronic obstructive bronchitis, or emphysema, or combinations of these conditions.
In 2005, 11.6 million U.S. adults (aged 18 and over) were estimated to have COPD. There is no cure for COPD, although treatment can make the individual more comfortable. Although tobacco smoking is the most critical risk factor for both development and progression of COPD, asthma, exposure to ambient pollutants in the home and workplace, and respiratory infections are also key factors.
The Center for Disease Control (CDC) advises that tobacco use is the key risk factor in COPD development and progression. However, only ten to twenty percent of smokers get COPD. Scientists now believe that within that group of smokers who develop COPD, genetic factors are likely to have been an influence.
The scientists also noted that people who have that particular gene are not necessarily destined to get COPD. The disease will likely be influenced by the interaction of multiple genetic factors with each other and with a number of environmental agents such as pollution.
Manning, like her father who was a cigarette smoker for most of his life, smoked heavily for over forty years. Manning’s father also developed COPD. Tests have not been done to determine whether the Mannings carry the gene that may influence COPD.
John R. Hoidal, a lung specialist, is working now on identifying candidate genes for COPD in his position as The Clarence M. & Ruth N. Birrer Presidential Endowed Chair of the Department of Internal Medicine at the University of Utah Medical School.
In 2001, Hoidal wrote in the European Respiratory Journal, “Various studies provide compelling evidence that genetic factors influence the development of COPD.” (“Genetics of COPD: present and future.” European Respiratory Journal, November, 2001, 18: 741-743).
Edwin K. Silverman, a genetic epidemiologist at Harvard Medical School, agreed in an e-mail interview, “I think that the evidence is quite strong that there are inherited risk factors for COPD, but there is a lot of controversy about what those genetic risk factors are.”
Silverman also stated, “It appears that inherited risk factors interact with cigarette smoking to increase the risk of COPD.” Dr. Silverman has had an ongoing interest in the genetic epidemiology of complex diseases, and has conducted research involving the genetic epidemiology of obstructive lung diseases including COPD and asthma.
The American Lung Association of Minnesota reports that COPD is becoming more prevalent in the African-American community. The CDC supports this observation – not only is there an increase in the disease in the black population, but there is also an increase in the death rate.
According to the CDC, during 1980-2000, the overall death rate for COPD increased 67 percent. The death rate from COPD for black people rose 87 percent. In 1980, 2,735 black deaths were attributed to COPD. This number rose to 6,375 in 2000.
Despite the increase in COPD rates in the African-American community, Dr. Silverman noted, “It is unknown whether the genetic risk factors for COPD are the same or different between ethnic groups.”
Although there is a habit of smoking in the Manning family and also incidences of COPD, there are many families with heavy smokers but no COPD. In the 2001 European Respiratory Journal article, Hoidal reported that, “The extent of cigarette smoking (pack-yrs and duration of smoking) only account for 15% of the variation in lung function, indicating that differences in susceptibility to COPD must exist.”
In our e-mail interview, Silverman concurred, “There does appear to be convincing familial clustering of COPD in response to smoking. Our study of severe, early-onset COPD subjects demonstrated that close relatives (like parent-child) who smoke cigarettes have a three-fold increased risk of COPD compared to smokers from the general population.”
Silverman added that nonsmoking relatives did not have any increased risk for COPD. He also indicated that there were other studies with similar results and concluded, that, “thus, it appears that inherited risk factors interact with cigarette smoking to increase the risk of COPD.”
As Hoidal and Silverman noted, there are various other studies that found that genetic factors are likely to influence the development of COPD. Examples are: Dr. Peter Pare and Dr. Andrew J. Sandford, lung specialists at the University of British Columbia who are examining genetic susceptibility for asthma and COPD.
Manning does not know whether or not genes played a role in her development of the disease. She does know for certain, however, that COPD is linked to cigarette smoking, and as a result, with each passing day, her fears grow that if her grandchildren become addicted to cigarette smoking they too might also develop COPD, and eventually die from the disease like her father did. Manning’s brother still smokes and she believes, although not sure, that one grandchild may have tried smoking.
The walls in Manning’s apartment are covered with photographs of her immediate family – five children, 18 grandchildren, 27 great grandchildren – and her extended family. “I used to love to get together with my family; we would barbeque and have fun. I would go to Como Park with the kids. They still visit me, but it’s not the same.”
Manning has been suffering from COPD since 1998 and was put on oxygen a year later. Her life has been forever altered, she said. “It destroys you,” observed Manning about her disease. “I used to be very active – play ball, track, and I had a very physical job. Now I can only walk a short distance – just down the hall – without getting terribly out of breath. I can’t even go to church, because I can’t climb the steps. I used to sing in the choir, but I can’t do that anymore either.”
Despite Manning’s disease, she is cheerful with a hearty laugh, a friendly demeanor and kind words for those she encounters. She is thankful to be alive and she cherishes each day. Manning’s message to smokers and nonsmokers is, “Think about what you want with your life. Smoking hurts you and others around you.”
Childhood respiratory infections, and breathing in other kinds of irritants, like pollution, dust or chemicals, may also cause or contribute to COPD, according to the ALA. Not smoking or quitting smoking for those who already smoke, however, is the best way to avoid developing COPD, advises the ALA.
Jennifer Holder is a recipient of The DNA Files 2007 Ethnic Media Science Journalism Fellowship. The Fellowship is offered by New America Media in collaboration with SoundVision Productions, a nonprofit media organization dedicated to strengthening coverage of science, technology, humanities and the arts. For more information about the DNA Files, go to www.dnafiles.org