Although we typically report laboratory-controlled studies, sometimes our most valuable information comes from large pools of data collected through real-world monitoring. For example, large datasets can be collected from survey data or health reports. A recently published study reported on a very large population with data obtained from health insurance records. These records contain information from 15 years (!) worth of health insurance claims from almost 1 million people. A few lucky researchers were able to get their hands on this data, and a study was conducted using the subjects who reported sleep apnea as one of their illnesses.
This study examined everybody in the database who was over the age of 20 when they reported their health conditions. From this subject pool, 6,816 people with recently diagnosed sleep apnea were compared with a control group of 27,248 people who did not suffer from sleep apnea. This control group was similar to the experimental group for age, sex, and other diseases. Subjects were excluded from the analysis if they had previously pulmonary (lung) breathing diseases or issues.
Within this population, it was found that the development of pneumonia in the sleep apnea population was much higher than in those without sleep apnea. This relationship was established even when controlling for things like age, sex, and the presence of other diseases, meaning that sleep apnea is an independent risk factor for the development of pneumonia. Not surprisingly, the older subjects who had sleep apnea had a higher chance for developing the disease. Interestingly, there was no difference between rates of pneumonia developing between those on sleep apnea treatment and those not being treated1.
So what is the link between sleep apnea and pneumonia, besides for the obvious point that both are breathing-related disorders? The authors of this study point out that repeated apneas and hypopneas throughout the night create certain susceptibilities for developing other disorders. Airway dysfunction that occurs within sleep apnea could contribute to the inhalation of saliva that contains pathogens. In addition, the repetitive disruption of sleep in this population may prevent the patient from falling into deeper stages of sleep. If this happens, immune functioning can become impaired, leaving the patient open to developing new sicknesses, including pneumonia. Within this study, there was no difference between the rates of pneumonia developing between treated (on CPAP) and non-treated subjects, confirming that weight loss is the first line of defense for those with sleep apnea.
1. Su VY, Liu CJ, Wang HK, Wu LA, Chang SC, Perng DW, Su WJ, Chen YM, Lin EY, Chen TJ, Chou KT. Sleep apnea and risk of pneumonia: a nationwide population-based study. CMAJ. 2014 Mar 3