Relationship between socioeconomic inequality and multimorbidity progression in UK Biobank data

Socio-economic status (SES) is associated with many adverse health outcomes, yet it remains unclear how SES relates to the rate at which people accumulate long-term conditions (LTCs) over time. We investigated this relationship between SES and disease accumulation using longitudinal disease tracking data.

We analyzed data from the UK Biobank study (n = 502,368, median age 58 years [range 37-73], 46% male at baseline) with a median follow-up of 15.8 years. We tracked accumulation of 80 specified LTCs (identified from hospital records using ICD-10 codes). Multistate models were used to estimate the transition rates between SES and incremental morbidity states (i.e., 0 to 1 LTC, 1 to 2 LTCs, until 7 to 8 + LTCs), with death as the absorbing state. SES indicators included education level, family income, Townsend Deprivation Index, and Index of Multiple Deprivation. The models were adjusted for age, sex, ethnicity, calendar year, current number of LTCs, and lifestyle factors.

Over 7.5 million person-years of follow-up, we observe a clear socioeconomic gradient in disease accumulation rates. All four SES indicators are associated with accelerated morbidity progression and mortality. The socioeconomic gradient is evident across all transition stages but notably stronger for the initial transition from health to the first LTC, where the lowest income group has a 71% higher transition rate (95% CI: 1.67-1.76).

Disadvantaged SES is associated with higher rates of progression to subsequent morbidities. These findings show the lasting impact of socioeconomic disadvantages on the widening health gap in later adulthood.