Asthma remains a cause of chronic illness in 12% of the UK population. Patients with high Body Mass Index (BMI) are more likely to be asthmatic and the weight increase predates the onset of asthma. Studies have found an asthma phenotype in association with high BMI, which occurs more commonly in women.
Although adult obesity is linked to birthweight and obesity is associated with asthma, research regarding the relationship between birthweight and asthma is not clear, especially the direction of the relationship. Longitudinal studies of birth cohorts have demonstrated that the tendency to asthma occurs early in life.
In this feasibility study, we plan to identify the number of patients with asthma diagnosis with a recorded BMI or birth weight and the number with birth weight recorded via Hospital Episode Statistics Admitted Patient Care(HES APC) and the mother-baby link.
In a future study, we will explore at what ages associations between BMI and asthma become significantly raised and will explore optimal interventions to target these life stages. This will help us understand whether interventions might best target pregnancy, childhood, and/or adulthood. High birth weight may be an indicator of underlying metabolic, hormonal, and/or immunological alternative pathway that begins long before asthma or weight gain.
The findings from this study will help develop a National Institute for Health Research grant application to investigate the association of asthma incidence in the high BMI female asthma phenotype. The terms of our funding for this work are purely for a feasibility study.
Our objective is to establish the feasibility of using CPRD to investigate the association between birthweight and asthma diagnosis in a future study.
The future study aims to identify points in development when an intervention may change outcomes and prevent asthma onset. The question we hope to address is to ask if birthweight can determine the tendency to asthma in this high BMI female asthma phenotype and if this differs for men. We know that weight reduction can improve asthma control, but no study has investigated if prevention of weight increase can prevent asthma incidence.
This feasibility study aims to:
1. Determine the numbers of patients with recorded birthweight in CPRD or linked hospital records.
2. Determine the numbers of asthma cases and the proportion with birthweight recorded in the primary care data.
3. Determine the earliest BMI or weight record for asthma cases.
4. Determine the numbers of asthma cases with recorded environmental factors (by IMD deprivation decile and smoking status).
5. All counts will be provided for men and women separately.
We request HES APC linkage to improve the ascertainment of patients with an asthma diagnosis and to ascertain birthweight recorded in the maternity table. The Mother-baby data will also be used to identify the mother of the included patients to identify the patient’s birthweight recorded in the maternity table. Access to the linked data will allow us to design a future study that will better inform policy changes for asthmatic patients in the future.
We request linked IMD data to help address any inequalities in patient care, environmental exposures, and/or patient outcomes. We request patient and practice level IMD due to the patient level IMD not being available for all patients.
Birth weights of patients (in Kg)
Asthma severity (‘severe asthma’=asthma hospitalisation, emergency department attendances and year of more than one course of oral steroids for asthma)
Asthma medication compliance (‘year good compliance year’ = greater than 70% use of inhaled corticosteroid per, <70% ‘bad compliance year’ =use of inhaled corticosteroid per year)
BMI of patients
Hormone Replacement Therapy (Regular use of medication: oestrogen based for 6 months or more, progestogen based for 6 months or more, both oestrogen and progestogen based for 6 months or more, treatment of menopause for 6 months or more)
Contraception (Regular use of medication for contraception for 6 months or more)
Number of completed pregnancies (livebirth(s)) and age at those pregnancies (‘pregnancy before age 35’ and ‘pregnancy after age 35’)
Medical conditions (wheeze, eczema, hay fever)
Antibiotics taken by patients’ mothers during pregnancy
Antibiotics taken by patients during infancy (0 years to 5 years)
Environmental factors
• IMD Deprivation index (in deciles) (patient level)
• IMD Deprivation index (in deciles) (practice level)
• Smoking (‘ever smoked’ for at least one year prior to asthma diagnosis. ‘Current smoking ‘as smoker at time of diagnosis. For smokers, we need the pack year history)
sadiyah Hand - Chief Investigator - University of East Anglia
Kathryn Richardson - Corresponding Applicant - University of East Anglia
Elena Kulinskaya - Collaborator - University of East Anglia
Kathryn Richardson - Collaborator - University of East Anglia
CPRD GOLD Mother-Baby Link;HES Admitted Patient Care;Patient Level Index of Multiple Deprivation;CPRD Aurum Mother-Baby Link;Practice Level Index of Multiple Deprivation (Standard)