Midlife Health in Britain and the US: A comparison of Two Nationally Representative Cohorts

BackgroundOlder adults in the United States (US) have worse health and wider socioeconomic inequalities in health compared to Britain. Less is known about how health in the two countries compares in midlife, a time of emerging health decline, including inequalities in health. MethodsWe compare measures of smoking status, alcohol consumption, obesity, self-rated health, cholesterol, blood pressure, and glycated haemoglobin using population-weighted modified Poisson regression in the 1970 British Cohort Study (BCS70) in Britain (N= 9,665) and the National Longitudinal Study of Adolescent to Adult Health (Add Health) in the US (N=12,297), when cohort members were aged 34-46 and 33-43, respectively. We test whether associations vary by early- and mid-life socioeconomic position. FindingsUS adults had higher levels of obesity, high blood pressure and high cholesterol. Prevalence of poor self-rated health, heavy drinking, and smoking was worse in Britain. We found smaller socioeconomic inequalities in midlife health in Britain compared to the US. For some outcomes (e.g., smoking), the most socioeconomically advantaged group in the US was healthier than the equivalent group in Britain. For other outcomes (hypertension and cholesterol), the most advantaged US group fared equal to or worse than the most disadvantaged groups in Britain. InterpretationUS adults have worse cardiometabolic health than British counterparts, even in early midlife. The smaller socioeconomic inequalities and better overall health in Britain may reflect differences in access to health care, welfare systems, or other environmental risk factors. FundingESRC, UKRI, MRC, NIH, European Research Council, Leverhulme Trust Research in contextO_ST_ABSEvidence before this studyC_ST_ABSThis study considered a range of seminal evidence published in academic journals, focusing on international comparisons of health, of which the majority has been conducted in older age cohorts (adults over the age of 50) in Britain and the US. We focused our search on cross-country comparisons and international surveys of ageing, such as the Health and Retirement Survey in the US, and the English Longitudinal Study of Ageing in Britain. We limited our search to English language publications and included studies that considered both overall differences in health, and differences in socioeconomic inequalities in health. The majority of considered studies found older adults in the US to have worse health than in Britain, and with greater evidence of inequalities for older adults in the US. However, older adults in Britain were more likely to exhibit worse health behaviours than those in the US. Added value of this studyThis study adds value by investigating health in early midlife (30s and 40s), a period less researched compared to older age. Midlife is an important time in the life course where early signs of decline can be observed and when there is still an opportunity to promote healthy aging. The importance of midlife is consistent with the need to understand healthy ageing as a life-long process. This study uses biomarkers as objective measures of cardiometabolic health and involved retrospective harmonisation of cohorts in Britain and the US, helping lay the groundwork for efforts to harmonise cohorts at younger ages and facilitate comparative work. Implications of all the available evidenceWe find that health in US adults is worse than their peers in Britain at even earlier ages (30s-40s years of age) than previously documented, especially for cardiometabolic measures. While associations of childhood socioeconomic status and later health were found in both Britain and the US, adult socioeconomic measures largely accounted for these associations. This finding is consistent with previous work and underscores the persistence of socioeconomic position across the life course, with sustained impacts on health. Policies aimed at improving health must consider this link between early and later life socioeconomic circumstances. We also find wider socioeconomic inequalities in health outcomes in the US than Britain. For some outcomes the most advantaged groups in the US have similar or worse health than the most disadvantaged groups in Britain. These findings, along with previously published evidence, have implications for policy and practice, as they suggest sociopolitical differences between the two countries that may drive different health profiles. Systematic differences between Britain and the US in terms of health care and welfare provisions may drive both worse health, and wider inequalities in the US.