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. 2023 Aug 28;23(1):1644.
doi: 10.1186/s12889-023-16369-1.

Educational inequality in multimorbidity: causality and causal pathways. A mendelian randomisation study in UK Biobank

Teri-Louise North  1 , Sean Harrison  2 , Deborah C Bishop  2 , Robyn E Wootton  2   3   4 , Alice R Carter  2 , Tom G Richardson  2 , Rupert A Payne  5   6 , Chris Salisbury  5 , Laura D Howe  2
Affiliations

Educational inequality in multimorbidity: causality and causal pathways. A mendelian randomisation study in UK Biobank

Teri-Louise North et al. BMC Public Health. .

Abstract

Background: Multimorbidity, typically defined as having two or more long-term health conditions, is associated with reduced wellbeing and life expectancy. Understanding the determinants of multimorbidity, including whether they are causal, may help with the design and prioritisation of prevention interventions. This study seeks to assess the causality of education, BMI, smoking and alcohol as determinants of multimorbidity, and the degree to which BMI, smoking and alcohol mediate differences in multimorbidity by level of education.

Methods: Participants were 181,214 females and 155,677 males, mean ages 56.7 and 57.1 years respectively, from UK Biobank. We used a Mendelian randomization design; an approach that uses genetic variants as instrumental variables to interrogate causality.

Results: The prevalence of multimorbidity was 55.1%. Mendelian randomization suggests that lower education, higher BMI and higher levels of smoking causally increase the risk of multimorbidity. For example, one standard deviation (equivalent to 5.1 years) increase in genetically-predicted years of education decreases the risk of multimorbidity by 9.0% (95% CI: 6.5 to 11.4%). A 5 kg/m2 increase in genetically-predicted BMI increases the risk of multimorbidity by 9.2% (95% CI: 8.1 to 10.3%) and a one SD higher lifetime smoking index increases the risk of multimorbidity by 6.8% (95% CI: 3.3 to 10.4%). Evidence for a causal effect of genetically-predicted alcohol consumption on multimorbidity was less strong; an increase of 5 units of alcohol per week increases the risk of multimorbidity by 1.3% (95% CI: 0.2 to 2.5%). The proportions of the association between education and multimorbidity explained by BMI and smoking are 20.4% and 17.6% respectively. Collectively, BMI and smoking account for 31.8% of the educational inequality in multimorbidity.

Conclusions: Education, BMI, smoking and alcohol consumption are intervenable causal risk factors for multimorbidity. Furthermore, BMI and lifetime smoking make a considerable contribution to the generation of educational inequalities in multimorbidity. Public health interventions that improve population-wide levels of these risk factors are likely to reduce multimorbidity and inequalities in its occurrence.

Keywords: Causality; Determinants; Education; Inequality; Mendelian randomization; Multimorbidity.

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Conflict of interest statement

TGR is an employee of GlaxoSmithKline outside of this work. AC is an employee of Novo Nordisk outside of this work. LH received a Career Development Award from the Medical Research Council for the submitted work, which also supported TLN; ARC received funding from the University of Bristol Medical Research Council Integrative Epidemiology Unit [MC_UU_00011/1 and MC_UU_00011/6]; NIHR Applied Research Collaboration West provides funding towards CS’s salary; National Institute for Health Research provides funding towards CS’s research expenses; in the past 36 months REW received a grant from the South-Eastern Norway Regional Health Authority [2020024], REW worked in a unit funded by the Medical Research Council [MC_UU_00011/3 and MC_UU_00011/7], REW had a previous postdoc funded by the Wellcome Trust [204895/Z/16/Z], RP received an institution-paid grant from the Medical Research Council, RP received an institution-paid grant from the National Institute for Health and Care Research; in the past 36 months REW wrote a report on literature relating smoking and mental health for the public charity ‘Action on Smoking and Health’; in the past 36 months REW received support for attending meetings and/or travel from (1) the Society for research on nicotine and tobacco New Investigator Award, (2) the Gro Harlem Brundtland Visiting Scholarship at the Centre for fertility and health Norwegian institute of public health, (3) an International Convention of psychological science travel grant; within the past 36 months RP has been the Chair of the Society of Academic Primary Care and has been a member (payment to institution) of the MHRA Pharmacovigilance Expert Advisory Group; within the past 36 months RP has had a personal paid role as Consultant Editor for the journal Prescriber; within the past 36 months ARC received an honoraria from the American Medical Association Memphis Chapter for delivering a Mendelian randomization workshop.

Figures

Fig. 1
Fig. 1
Multivariable regression (MVR) and Mendelian Randomization (MR) results for the causal effect (Risk Difference, RD) of each exposure on multimorbidity status (2 + chronic conditions)
Fig. 2
Fig. 2
Mediation of the educational inequality in multimorbidity (2 + chronic conditions) by BMI, lifetime smoking index, and BMI and lifetime smoking index combined. Analyses conducted using multivariable regression (MVR) and Mendelian randomization (MR). Estimate presented is the Proportion Mediated (PM)
See this image and copyright information in PMC

References

    1. Centre NG. Multimorbidity: clinical assessment and management. London: National Institute for Health and Care Excellence; 2016.
    1. Barnett K, Mercer SW, Norbury M, Watt G, Wyke S, Guthrie B. Epidemiology of multimorbidity and implications for health care, research, and medical education: a cross-sectional study. The Lancet. 2012;380(9836):37–43. doi: 10.1016/S0140-6736(12)60240-2. - DOI - PubMed
    1. US Department of Health and Human Services. Multiple chronic conditions - a strategic framework: optimum health and quality of life for individuals with multiple chronic conditions. Washington, DC; 2010.
    1. Katikireddi SV, Skivington K, Leyland AH, Hunt K, Mercer SW. The contribution of risk factors to socioeconomic inequalities in multimorbidity across the lifecourse: a longitudinal analysis of the Twenty-07 cohort. BMC Med. 2017;15(1):152. doi: 10.1186/s12916-017-0913-6. - DOI - PMC - PubMed
    1. Mutz J, Roscoe CJ, Lewis CM. Exploring health in the UK Biobank: associations with sociodemographic characteristics, psychosocial factors, lifestyle and environmental exposures. BMC Med. 2021;19(1):240. doi: 10.1186/s12916-021-02097-z. - DOI - PMC - PubMed

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