LIvES: Lifestyle, Energy Expenditure, and Sleep in Obstructive Sleep Apnoea (A pilot study)

Abstract

Background: Obesity is a major health issue, and one of the leading causes of Obstructive Sleep Apnoea (OSA). OSA occurs when the upper airway is repetitively obstructed, either entirely or partially, whilst sleeping. This causes reduced or lack of airflow into the lungs, commonly resulting in snoring or disturbed sleep that leads to daytime sleepiness, increased risk of motor or work-related accidents, and overall impaired quality of life. As rates of obesity increase, it can be expected that so too will cases of OSA. Previous overseas research has found that overnight energy expenditure (EE) is greater when OSA is untreated, whilst Continuous Positive Airway Pressure (CPAP), the “gold standard” treatment, has been linked to weight gain due to a decrease in overnight energy expenditure but mechanisms are not well understood. This means losing weight may become more difficult with CPAP treatment. Objective: To determine if there is a decrease in overnight energy expenditure following the initiation of CPAP treatment in patients newly diagnosed with Obstructive Sleep Apnoea, who are living in the Wellington area. Design: In this pilot study, participants were recruited prior to their scheduled sleep assessment by means of polysomnography (PSG) (a multi-component sleep assessment tool) at the WellSleep Sleep Investigation Centre at Bowen Hospital. Participants were also recruited following PSG confirming OSA, but prior to initiating CPAP treatment. The study was divided into three stages. In stage one, participants wore a SenseWear® device on an armband consecutively for three days and nights, whilst keeping a three day food record and three day sleep diary. In stage two, participants initiated CPAP treatment following OSA diagnosis, and continued to receive treatment. Stage three was identical to stage one, but whilst continuing CPAP treatment. Data on EE and sleep patterns were collected from SenseWear® devices by exporting the data to the SenseWear® Professional 8.1 program by Bodymedia® on a computer. Sleep diaries confirmed sleep data. Kai-culator (v 1.11), a University of Otago dietary analysis program, was used to calculate energy intake from food diaries. The strength of the relationship between CPAP and EE was measured using Pearson correlation coefficient. EE and energy intake before and during CPAP treatment were compared using paired t-tests. Results: Mean energy intake per day was 9629KJ (SD 3130) in stage one, and 9271KJ (SD 2107) in stage three, with no significant difference between each stage (p=0.89). Mean EE per hour of total sleep time was 351KJ (SD 86) in stage one, and 340KJ (SD 82) in stage three, with no significant difference between each stage (p=0.36). CPAP use was strongly correlated with EE; EE decreased as hours of CPAP use increased (p=0.014, R2=0.485). Conclusion: The current study found a significant relationship between EE and CPAP; energy expenditure during sleep reduced with longer CPAP use. However, no overall differences in EE or EI were seen before and during initial CPAP use. These results indicate there is the potential for weight gain to occur over time once initiated on CPAP treatment, particularly if energy intake remains unchanged. A longer term study with a larger sample size will help clarify the extent of this relationship.