New research reveals the association between the effects of sleep apnea and gout beyond the first year of sleep apnea diagnosis.
Until recently, the effects of sleep apnea on developing gout have not been well studied despite both being associated with high uric acid levels. Gout is a painful condition characterized by inflammation of joints and is caused by high levels of uric acid. Sleep apnea has also been found to be associated with high levels of uric acid.
Gout and sleep apnea have a similar prevalence in the United Kingdom, with similar risk factors and similar associations to other diseases such as high blood pressure, heart disease, obesity and diabetes. Despite these similarities, the effects of sleep apnea on the risk of gout have not been well studied.
Sleep apnea leads to an increased production of uric acid
Sleep apnea leads to temporary interruptions in oxygen supply, which can cause a faster turnover of nucleotides in the body. This generates purines, which is then converted to uric acid. This increased production of uric acid is the probable explanation for how the effects of sleep apnea can be associated with the development of gout.
A previous study found that people with sleep apnea had a 50% greater chance of experiencing gout after a one-year follow-up, however, the effects of sleep apnea on the risk of gout beyond that have not been studied. Therefore, researchers from the United Kingdom recently examined the association between sleep apnea and gout over a longer follow-up period and published their results in Arthritis & Rheumatology.
The retrospective cohort study identified patients aged 18 years and older with a diagnosis of sleep apnea from the Clinical Practice Research Datalink, a large database in the United Kingdom that routinely collects primary care information, and is reflective of the general population. They matched each patient with up to four individuals without a sleep apnea diagnosis for comparison. Both groups were similar in characteristics. The study’s main outcome was the time until the first diagnosis of gout, and the median follow-up period was 5.8 years.
Highest risk of gout observed during the first two years after sleep apnea diagnosis
Nearly 5% of sleep apnea patients developed gout during the follow-up period versus 2.6% of the comparison group. The incidence rate of gout per 1000 person-years was 7.83 and 4.03 in the sleep apnea and comparator group, respectively. A person-year is defined by the number of follow-up years multiplied by the number of people analyzed in the study.
The highest risk of developing gout was observed to be during the first one to two years after being diagnosed with sleep apnea, however, an increased risk remained present throughout the whole follow-up period. The effects of sleep apnea on increased gout risk were found in all BMI categories, with the highest gout risk being observed in people with a normal BMI. Although there is the potential for misclassification of gout diagnosis or sleep apnea diagnosis, these were assessed to have been unlikely to occur, thus not affecting the study’s results.
Sleep apnea is often treated with continuous positive airways pressure (CPAP), which ensures oxygen levels are not interrupted. In theory, this correction in oxygen levels should help to lower uric acid production levels and decrease the risk of gout. However, this theory would have to be studied further in trials before conclusions can be made on CPAP treatment in sleep apnea patients to prevent or treat gout.
Written by Maggie Leung, PharmD
References:
- Blagojevic-Bucknall, M., Mallen, C., Muller, S., Hayward, R., West, S., Choi, H., & Roddy, E. (2018). The risk of gout among patients with sleep apnea: A matched cohort study. Arthritis & Rheumatology. doi:10.1002/art.40662
- Peters, D. (2018, August 30). Obstructive Sleep Apnea Linked with Higher Risk of Gout. Retrieved from https://newsroom.wiley.com/press-release/arthritis-rheumatology/obstructive-sleep-apnea-linked-higher-risk-gout
