Is Asthma in Subjects With Obstructive Sleep Apnoea (OSA) Due to Dysanapsis

There is no evidence that the World Wide prevalence of asthma is declining. There is some evidence that this Western disease may give the appearance of declining prevalence due to improved healthcare. However evidence from the Office of National Statistics suggests that the mortality rate for asthma may be increasing year on since 2007 until 2017. The true burden of asthma in the United Kingdom is difficult to ascertain.

Obesity has effects on lung function which lead to low functional residual capacity and low end reserve volume. This leads to rapid shallow breaths near to the airway closing pressure and lung closing volume as illustrated in this review. This suggests that obesity itself may be a source of breathlessness.

High Body Mass Index (BMI) has been shown to be associated with asthma. It was also associated with wheeze that is not asthma. This finding suggests that obesity in itself may be linked to wheeze which is not asthma. It has been shown in children that sleep disordered breathing is associated with asthma as well as wheeze. Obese children are known to display dysanapsis (airway cross sectional area is small for the size of the lung) whether associated with or without asthma, however if associated with asthma, the severity of asthma can be worse.

AIM: To investigate if asthma is truly associated with Sleep disordered breathing in adult subjects. To investigate if there is an association of wheeze with dysanapsis in patients with sleep disordered breathing

NULL HYPOTHESIS: There is no difference between subjects who have sleep disordered breathing with asthma and those subjects who have sleep disordered breathing without asthma, with respect to lung function parameters.

Methods

Initially the investigators' aim is to interrogate clinical records and look at lung function testing in subjects with and without asthma who attend the sleep disordered breathing clinic. The investigators intend to investigate 100 with asthma in the sleep clinic and 100 without asthma in the sleep clinic. The Investigators will also look at eosinophil results of those with asthma compared to those without asthma and any markers of atopy.

The investigators will use Statistical Package for the Social Sciences (SPSS) to undertake simple frequency analysis and cross tabs as well as odds ratio from binary logistic regression.

References - Refer to References Section

Appendix 1

Data Collection Sheet for those with confirmed diagnosis of Obstructive sleep apnoea

Name and Date of Birth and details

Age

Weight ______Height___________Body Mass Index _________Gender at birth ___Male____Female___ Asthma diagnosis made by General Practitioner or Respiratory physician or no diagnosis of asthma (circle correct)

DATE of Test ___/___/___FEV1_______FEV1%_______

FVC_________FVC%__________

DATE of Test ___/___/___FEV1_______FEV1%_______

FVC_________FVC%__________

Dysanapsis FEV1/FVC <0.8 Yes/No FEV1/FVC <0.7 Yes/No (circle correct)

AHI/hr 5-15 16-29 >30 (circle correct)

Eosinophil count MAX in past 12 months________x109/L MAX ever ______ x109/L

DATE________

RAST test positive for which antigens

Smoking history start age________________ Pack years________________

Inclusion criteria

• Any subject in Obstructive Sleep Apnea clinic.

Exclusion criteria

• Only exclusion criteria is if they have no recorded lung function in their notes