Higher Levels of Bilirubin Associated With Lower Risk of Respiratory Disease
Bilirubin is a compound produced by the breakdown of hemoglobin from red blood cells. When levels are abnormally high, it indicates liver dysfunction, such as cirrhosis, hepatitis, or gallstones, or blood disease such as sickle cell anemia. Researchers from University College London have found a positive aspect of slightly higher levels of bilirubin – it may indicate a reduced risk of lung cancer and chronic obstructive pulmonary disease (COPD).
Bilrubin at Upper End of Normal Reduces Respiratory Disease Risk
Laura J. Horsfall MSc and colleagues examined the association between serum bilirubin levels and the incidence of respiratory diseases in more than 500,000 adults who were included in a large primary care research database called the Health Improvement Network. Data was collected between January 1988 and December 2008.
The researchers found that levels of bilirubin at the upper end of the normal range were associated with a reduced risk of respiratory disease and all-cause mortality. The team estimates that for each 0.1-mg/dL increase in bilirubin level, there was an associated decrease in lung cancer rates by 8% in men and 11% in women. An 0.1-mg/dL increase in the blood component was associated with a 6% decrease in COPD for both men and women.
The normal range for total bilirubin is 0.3 to 1.9 mg/dL.
Horsfall suggests that bilirubin may have cytoprotective properties, including antioxidant and anti-inflammatory effects. “Experimental studies using animal models support a protective effect of increased bilirubin against respiratory injury by environmental stressors,” write the authors in the Journal of the American Medical Association.
There is no specific action that a person can take to increase bilirubin levels for protection against lung cancer or COPD, except perhaps to limit caffeine intake and increase exercise. Caffeine can decrease bilirubin measurements, according to the National Institutes of Health, while strenuous exercise can increase levels. Other factors, such as eating a healthy low-cholesterol diet and avoiding alcohol and drugs can keep the liver healthy, which should maintain a normal value for bilirubin.
Avoidance of tobacco smoke exposure is the primary lifestyle change that can reduce the risk of respiratory disease.
Horsfall L, et al "Serum bilirubin and risk of respiratory disease and death" JAMA 2011; 305: 691-697.