Prevalence and early-life determinants of mid-life multimorbidity: evidence from the 1970 British birth cohort

Abstract ObjectivesWe sought to: (1) estimate the prevalence of multimorbidity at age 46-48 in the 1970 British Cohort Study—a nationally representative sample in mid-life; and (2) examine the association between early-life characteristics and mid-life multimorbidity in the 1970 British Cohort Study. DesignProspective longitudinal birth cohort. SettingA community based sample from the 1970 British Cohort Study (BCS70). ParticipantsAll surviving children born in mainland Britain in a single week in April 1970; the analytical sample was those with valid data at age 46-48 (n=7,951; 2016-2018). Main outcome measureMultimorbidity was operationalised as a binary indicator of two or more long-term health conditions where at least one of these conditions was of physical health. It also included symptom complexes (e.g. chronic pain), sensory impairments, and alcohol problems. ResultsPrevalence of mid-life multimorbidity was 33.8% at age 46-48. Those with fathers from unskilled social occupational class (vs. professional) at birth had 43% higher risk of mid-life multimorbidity (risk ratio=1.43, 95% confidence interval 1.15 to 1.70). After accounting for a range of potential child and family confounders, an additional kilogram of birthweight was associated with 10% reduced risk of multimorbidity (risk ratio=0.90, 95% confidence interval 0.84 to 0.96); a decrease of one body mass index point at age 10 was associated with 3% lower risk (risk ratio=1.03, 95% confidence interval 1.01 to 1.05); one standard deviation higher cognitive ability score at age 10 corresponded to 4% lower risk (risk ratio=0.96, 95% confidence interval 0.91 to 1.00); an increase of one internalising problem at age 16 was equated with 4% higher risk (risk ratio=1.04, 95% confidence interval 1.00 to 1.08) and of one externalising problem at age 16 with 6% higher risk (risk ratio=1.06, 1.03 to 1.09). ConclusionPrevalence of multimorbidity was high in mid-life (33.8% at age 46-48) in Britain, with those in a more disadvantaged social class a birth being disproportionally affected. Potentially modifiable early-life exposures including early-life social circumstances, cognitive, physical and emotional development were associated with mid-life multimorbidity. What is already known on this topic?Due to differences in outcome definition, estimates of multimorbidity prevalence in mid-life (age 40-60) have varied extensively in high-income countries—from 15 to 80% between 1961 and 2013.There is a lack of contemporary national data in Great Britain describing the burden and nature of multimorbidity according to an agreed definition.The association between early-life risk factors and individual health conditions have been widely studied, however it is unknown if they are associated with multimorbidity. What this study addsPrevalence of multimorbidity in mid-life (age 46-48) was 33.8% in a nationally representative birth cohort in 2016-2018.Disadvantaged early-life parental social class, lower birthweight, lower cognitive ability, higher childhood body-mass index, and a higher number of internalising and externalising problems were found to be associated with a higher mid-life multimorbidity.