Cow’s milk allergy (CMA) is an allergy that occurs after consuming cow’s milk or dairy products. This includes cheese, yoghurt and butter. It is one of the most common food allergies, affecting about 1 in 100 children under 2 years old. The symptoms vary from skin redness and itchiness to vomiting and diarrhoea. It can also cause wheezing and shortness of breath or general discomfort. Doctors prescribe low-allergy formula milk for children with suspected CMA who need formula milk. In England, doctors prescribe much more low-allergy formula milk compared with 10 years ago. Low-allergy formula milk prescriptions have also increased in other countries. Low-allergy formula milks have more "free sugars" than standard formula milk and breastmilk. Too much 'free sugars' can cause dental decay and childhood obesity.
We will use routinely collected data from primary care to see how many children in England got low-allergy formula milk by age 2. We will also see if certain factors make a child more likely to get low-allergy formula milk. We will compare children who got low-allergy formula milk to those who did not. These findings will help us understand which children are more likely to get low-allergy formula milk. This will enable us to develop strategies to improve prescribing of low-allergy formula milk. This has potential to reduce negative health effects by limiting future increases in low-allergy formula milk prescribing.
Background:
Cow’s milk allergy (CMA) affects about 1% of children under 2 years.1 Prescription rates of low-allergy formula milk are up to 15 times higher than expected, suggesting CMA overdiagnosis.2,3 The consequences of exposure of large numbers of infants to low-allergy formula milk designed to manage CMA are not fully understood.3-6 Low-allergy formula milks have higher amounts of ’free sugars’ which potentially carries risks to child health and development, in particular dental decay and childhood obesity.3,6-9
Aim: Describe the prevalence and factors associated with prescription of low-allergy formula milk in England.
Study population: All children born in England registered with general practice from January 2008-December 2021.
Outcomes:
•Proportion and characteristics of children in England prescribed low-allergy formula milk by age 2 years
•Prescribing frequency and duration of low-allergy formula milk in children under 2 years in England
•Healthcare utilisation associated with prescription of low-allergy formula milk (such as dental extractions)
•Factors (service - GP practice, clinical - child/maternal and sociodemographic) associated with prescription of low-allergy formula milk
Data sources:
CPRD Aurum – identify community prescribing, health and demographic information for children.
HES APC – explore healthcare utilisation (dental extractions) associated with prescription of low-allergy formula milk.
IMD data – analyse if associations vary by deprivation.
Mother-baby link and pregnancy register – explore potential maternal factors associated with prescription of low-allergy formula milk.
Study design:
Retrospective cohort study.
Analysis: Descriptive statistics and regression to explore associations between factors and low-allergy formula milk prescriptions.
Intended public health benefit:
This research will increase our understanding of the current number of children prescribed low-allergy formula milk and the factors that are associated with prescription rates in England. This helps clinicians to recognise children at higher risk of potentially unnecessary low-allergy formula milk prescriptions and raise awareness of the potential harms of CMA overdiagnosis.
Primary:
Proportion and characteristics of children in England prescribed low-allergy formula milk by age 2 years ; Prescribing frequency and duration of low-allergy formula milk prescribed to children under 2 years in England
Secondary:
Difference in healthcare utilisation associated with prescription of low-allergy formula milk ; Factors (service - GP practice, clinical - child/maternal and sociodemographic) associated with prescription of low-allergy formula milk
Robert Boyle - Chief Investigator - Imperial College London
Nikita Punjabi - Corresponding Applicant - Imperial College London
Dougal Hargreaves - Collaborator - Imperial College London
Kimberley Foley - Collaborator - Imperial College London
Mark Cunningham - Collaborator - Imperial College London
Sonia Saxena - Collaborator - Imperial College London
HES Admitted Patient Care;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation;CPRD Aurum Mother-Baby Link;CPRD Aurum Pregnancy Register