Socioeconomic inequalities in prevalence and development of multimorbidity across adulthood: A longitudinal analysis of the MRC 1946 National Survey of Health and Development in the UK

BackgroundWe aimed to estimate multimorbidity trajectories and quantify socioeconomic inequalities based on childhood and adulthood socioeconomic position (SEP) in the risks and rates of multimorbidity accumulation across adulthood. Methods and findingsParticipants from the UK 1946 National Survey of Health and Development (NSHD) birth cohort study who attended the age 36 years assessment in 1982 and any one of the follow-up assessments at ages 43, 53, 63, and 69 years (N = 3,723, 51% males). Information on 18 health conditions was based on a combination of self-report, biomarkers, health records, and prescribed medications. We estimated multimorbidity trajectories and delineated socioeconomic inequalities (based on childhood and adulthood social class and highest education) in multimorbidity at each age and in longitudinal trajectories.Multimorbidity increased with age (0.7 conditions at 36 years to 3.7 at 69 years). Multimorbidity accumulation was nonlinear, accelerating with age at the rate of 0.08 conditions/year (95% CI 0.07 to 0.09, p < 0.001) at 36 to 43 years to 0.19 conditions/year (95% CI 0.18 to 0.20, p < 0.001) at 63 to 69 years. At all ages, the most socioeconomically disadvantaged had 1.2 to 1.4 times greater number of conditions on average compared to the most advantaged. The most disadvantaged by each socioeconomic indicator experienced an additional 0.39 conditions (childhood social class), 0.83 (adult social class), and 1.08 conditions (adult education) at age 69 years, independent of all other socioeconomic indicators. Adverse adulthood SEP was associated with more rapid accumulation of multimorbidity, resulting in 0.49 excess conditions in partly/unskilled compared to professional/intermediate individuals between 63 and 69 years. Disadvantaged childhood social class, independently of adulthood SEP, was associated with accelerated multimorbidity trajectories from age 53 years onwards.Study limitations include that the NSHD cohort is composed of individuals of white European heritage only, and findings may not be generalizable to the non-white British population of the same generation and did not account for other important dimensions of SEP such as income and wealth. ConclusionsIn this study, we found that socioeconomically disadvantaged individuals have earlier onset and more rapid accumulation of multimorbidity resulting in widening inequalities into old age, with independent contributions from both childhood and adulthood SEP. Author summary Why was this study done? Multimorbidity-2 or more chronic conditions in an individual-has several consequences including reduced quality of life, reduced life expectancy, and complex healthcare needs.Socioeconomic disadvantage is associated with both earlier onset (at younger ages) and greater burden of multimorbidity. However, less is known about how multimorbidity develops across adulthood and into older ages in the same individuals and differences in its development by childhood and adulthood socioeconomic position (SEP). What did the researchers do and find? Longitudinal multimorbidity trajectories were estimated between ages 36 and 69 years, and whether these trajectories differed by childhood (father's social class) and adulthood SEP (participant's own social class and educational level).We found that throughout follow-up, the most socioeconomically disadvantaged had 1.2 to 1.4 times greater number of health conditions on average compared to the most advantaged.On average, multimorbidity increased across adulthood and into older ages in both socioeconomically disadvantaged and advantaged groups. However, the rate at which multimorbidity increased across adulthood differed by SEP, with those from the most disadvantaged backgrounds having worse trajectories. In other words, adverse SEP was associated with more rapid accumulation of multimorbidity.Childhood and adulthood SEP were independently associated with multimorbidity across adulthood. This indicates that childhood socioeconomic disadvantage is still evident in later life over and above adulthood socioeconomic circumstances. What do these findings mean? The independent and long-lasting shadow of childhood SEP on the experience and the rate of accumulation of multimorbidities in later life highlight the need for interventions early in life to minimise inequalities in later life health.This calls for population-based interventions in early life and through the lifecourse to reduce the impact of childhood and adulthood inequalities, along with better access and delivery of healthcare for the more vulnerable to help reduce the burden of multimorbidity.