Rationale Healthcare demand in England is projected to increase further over the coming decades. As many chronic conditions share amenable risk factors, we aimed to quantify the potential impact of improving risk factor exposure levels on the burden of major illness in England from 2023-2043.

Methods We used the validated IMPACT_NCD England microsimulation model to simulate a close-to-reality synthetic population of adults in England from 2013-2043, modelling their sociodemographic characteristics, exposure to 8 amenable risk factors (body mass index (BMI), smoking, environmental tobacco smoke, physical activity, fruit, vegetables, total cholesterol, systolic blood pressure (SBP)), and 20 chronic conditions that comprise the Cambridge Multimorbidity Score (CMS). The model combines data from linked primary care records (Clinical Practice Research Datalink Aurum, Hospital Episodes Statistics, and Office for National Statistics (ONS) Mortality data), Health Survey for England, ONS population estimates, systematic reviews and meta-analyses.

We simulated two levels of improved risk factor exposures over 20 years (2023-2043):

1. optimal risk factor exposure levels

2. 10% improvement in exposure levels compared to a baseline of continuing trends

For each, we simulated the 8 risk factors individually, then all risk factors together (18 scenarios).

We defined our primary health outcome of ‘major illness’ as a CMS score greater than 1.5. We present the absolute and relative differences in projected prevalence of major illness from the improvement scenarios, compared to a baseline scenario of continuing trends in risk factors.

Medians (95% uncertainty intervals) are presented from 100 model runs, scaled to ONS population projections. Analyses were conducted using R v4.3.2.

Results In preliminary results, the biggest contributor to incident major illness is BMI, then smoking, SBP, and fruit and vegetable consumption. If all risk factor levels were at the optimal level, this could reduce prevalence of major illness in 2043 by 3.52 percentage points (2.81,4.15) compared to a baseline scenario of continuing trends in risk factors. This equates to a relative reduction of 11.30% (9.01%,13.33%) compared to the baseline.

With a 10% improvement in all 8 risk factor exposure levels, projected prevalence of major illness in 2043 could be 0.46 percentage points (0.34,0.60) lower than with continuing exposure trends; a relative reduction of 1.48% (1.10%,1.94%).

Discussion Our results suggest prevention strategies should focus on reducing population-level exposures of BMI, SBP, and smoking. However, even with substantial improvements in risk factor exposures, the burden of major illness is likely to remain large as the population demographic ages.