Snoring Affects Development Of Chronic Brochitis, Study
29 Jan 2008
A study by researchers in South Korea found that snoring influenced the development of chronic bronchitis, but how and why remained somewhat of a mystery.
The research was carried out by scientists at Korea University Ansan Hospital, in Ansan, South Korea, and is published in the 28th January issue of the Archives of Internal Medicine.
Previous research had already found that snoring is more common in people who have chronic bronchitis, but few studies have examined the link between snoring and onset of chronic bronchitis.
Bronchitis is classed as a subcategory of Chronic Obstructive Pulmonary Disease (COPD) and occurs when the air passages or tubes (bronchi) in the lungs become inflamed. There are two types: acute and chronic. Acute bronchitis usually follows an infection and either resolves on its own or with treatment.
Chronic bronchitis is usually caused by habitual exposure to chemicals and particles that irritate the lungs, such as from smoking tobacco products or working in a polluted environment every day. Chronic bronchitis is characterized by over-secretion of mucus, with a cough that does not go away easily (persists for more than 3 months in 2 consecutive years).
For this study, which ran from June 2001 to January 2003, the researchers recruited 5,015 male and female Korean citizens as participants. When the study started their ages ranged from 40 to 69 years.
The participants underwent comprehensive health exams and interviews and also filled in questionnaires at Korea University Ansan Hospital. From the original cohort, 4,270 participants (52 per cent men and 48 per cent women) went on to the first 2 year follow-up, and those who met the same inclusion criteria were followed for another two years. The total follow-up period was 4 years, finishing in November 2006.
The questionnaires they filled in at the beginning of the study asked the participants about their snoring, and the researchers noted all new cases of chronic bronchitis that arose during the 4 year follow-up. Participants who reported existing symptoms of bronchitis at the start of the study were excluded from the follow up (for instance if they had cough and sputum on most days for at least 3 months a year).
When the researchers examined and analysed the results they found:
314 new onset cases of chronic bronchitis in the 4 year follow up.
This is equivalent to an incidence rate of 27.1 cases per 1,000 person years (a measure commonly used by epidemiologists in public health fields).
After removing the effect of age, smoking, and other demographic and risk factors, they found snoring was significantly linked to new onset chronic bronchitis, and the more frequent the snoring, the stronger the link.
The risk of developing chronic bronchitis was 25 per cent higher for participants who snored 5 times or less per week compared with those who never snored.
This risk rose to 68 per cent for those who snored 6 to 7 times a week.
Grouping results according to risk factors, such as smoking status, type of job and BMI (body mass index) showed that the link between snoring and chronic bronchitis onset was stronger among non-smokers, house workers, and people who were overweight.
Non smokers who snored had a 39 per cent higher risk of developing chronic bronchitis compared with non smokers who never snored.
For smokers who never snored this risk was 31 per cent higher.
But for smokers who snored this risk was higher at 86 per cent.
The researchers concluded that:
"This prospective study observed that snoring is associated with chronic bronchitis. Our findings provide support for the hypothesis that snoring influences the development of chronic bronchitis."
A research fellow at the University of Michigan Sleep Disorders Center, Dr Robert Keeton, told the Washington Post that he found the study interesting, but would not call it conclusive.
"It can't be something you can cite to tell patients in the clinic that they have chronic bronchitis because they snore," he told the paper.
He also commented on the suggestion made by the researchers, who proposed two reasons for their findings. One was that the vibrations of snoring possibly cause inflammation of the bronchi, and the other possibility is the bronchi become inflamed, the snoring follows, and this lead to sleep apnea, a condition where breathing stops or is very shallow for about 20 seconds.
Keeton said a common cause of snoring is obstructive sleep apnea and it was not unusual for people to have such symptoms.
Another expert interviewed by the paper suggested the explanation around sleep apnea warrants further investigation, as sleep apnea was already known to be associated with increased inflammation in the body.
"Association of Snoring With Chronic Bronchitis."
Inkyung Baik; Jehyeong Kim; Robert D. Abbott; Soonjae Joo; Kihwan Jung; Sungyong Lee; Jaejeong Shim; Kwangho In; Kyungho Kang; Sehwa Yoo; Chol Shin.
Arch Intern Med 2008;168(2):167-173.
Vol. 168 No. 2, January 28, 2008