In a recent study published in Nature Communications, researchers evaluated the impact of the United Kingdom (UK) Soft Drinks Industry Levy (SDIL) on childhood asthma hospital admission rates in England.
Study: The UK Soft Drinks Industry Levy and childhood hospital admissions for asthma in England. Image Credit: VDZ3 Media/Shutterstock.com
Background
The UK Scientific Advisory Committee on Nutrition (SACN) recommends that free sugar consumption be below 5% of total energy intake. Still, current intake levels are at least twice this and three times higher in adolescents.
Sugar-sweetened beverages (SSBs) are a major source of free sugar and are linked to non-communicable diseases like obesity, diabetes, and cardiovascular disease, as well as asthma. A meta-analysis found higher asthma prevalence among high SSB consumers.
The UK SDIL, implemented in April 2018, aimed to reduce sugar content in drinks. Further research is needed to explore the long-term health impacts of the UK SDIL and to understand the underlying mechanisms linking sugar reduction to decreased asthma incidence.
About the study
National Health Service (NHS) hospital admissions for asthma (International Classification of Diseases (ICD)-10 code: J45) in children aged 5-18 years were analyzed using Hospital Episodes Statistics (HES) data.
Analyses were conducted overall by age groups (5-9, 10-14, and 15-18 years) and by the Index of Multiple Deprivation (IMD) quintile. Admissions for children under five were excluded due to diagnostic challenges.
The study period was from January 2012 to February 2020, encompassing the SDIL announcement (March 2016) and implementation (April 2018) and ending before the first coronavirus disease 2019 (COVID-19) lockdown to avoid confounding factors.
Interrupted time series (ITS) analyses evaluated the impact of the SDIL on childhood asthma admissions, comparing observed rates to a counterfactual scenario without the SDIL. Groupwise admissions were converted to incidence rates per 100,000 population, with models adjusted for months with significant changes in admission rates.
Counterfactual scenarios were modeled using pre-announcement data, with confidence intervals estimated by the delta method. Autocorrelation was addressed using Durbin-Watson tests and autocorrelation-moving average (ARIMA) models to minimize the Akaike information criterion (AIC).
Statistical analyses were performed in R version 4.1.0. Data were provided in an aggregated, anonymized state and obtained through a data-sharing agreement with NHS Digital.
Study results
The mean incidence rates of hospital admissions for asthma in children during the pre-announcement and post-announcement periods reveal significant inequalities. Children from the most deprived areas experienced nearly three times the hospital admission rates for asthma compared to those from the least deprived areas, with rates of 26.4/100,000 persons/month (p/m) and 9.3/100,000 p/m, respectively.
Additionally, younger children had higher incidence rates, with those aged 5-9 having approximately double the rate of hospital admissions compared to children aged 15-18 years.
In children aged 5-18 years, there was an overall absolute reduction in hospital admissions for asthma of 4.0 (2.4, 5.7)/100,000 p/m, or a relative reduction of 20.9% (95% CI: 29.6, 12.2), compared to the counterfactual scenario where the SDIL was neither announced nor implemented.
Upward trends in overall asthma admissions were observed until a few months after the SDIL announcement, followed by a downward trend. Seasonal variations showed dips in admissions in April and August, coinciding with school holidays, and large spikes in early autumn, particularly in September.
This peak in September aligns with the start of the school year, a time associated with increased exposure to respiratory viruses, allergens, and stress, as well as lapses in the routine use of preventer inhalers during the summer.
Each age group demonstrated upward trends in asthma hospital admissions from the start of the study period. However, significant reductions were observed 22 months after the implementation of the SDIL compared to the counterfactual scenario.
Children aged 5-9 and 10-14 years experienced relative reductions of 18.6% (95% CI: 30.0, 7.2) and 24.3% (95% CI: 32.1, 16.5), respectively, with visualizations indicating a reversal of the upward trend post-SDIL announcement.
Adolescents aged 15-18 years saw a relative reduction of 15.6% (95% CI: 19.7, 11.5), with a flattening but not a reversal of the pre-announcement upward trend in hospital admissions.
Hospital admissions for childhood asthma decreased across all deprivation groups. Absolute reductions were 4.8 (7.4, 2.3)/100,000 p/m in the most deprived quintiles and 3.4 (4.4, 2.3)/100,000 p/m in the least deprived quintiles.
Relative reductions were 15.5% (95% CI: 23.7, 7.2) and 26.4% (95% CI: 34.6, 18.1), respectively. Absolute reductions were relatively consistent across different IMD quintiles, though there was evidence of higher relative reductions in less deprived areas.
Conclusions
The findings align with previous studies linking SSB consumption to asthma, but this quasi-experimental design offers stronger evidence for a causal relationship.
The results suggest that similar SSB taxes in other countries could reduce hospital admissions for childhood asthma and improve public health.