Are Recent Cohorts Getting Worse? Trends in US Adult Physiological Status, Mental Health, and Health Behaviors Across a Century of Birth Cohorts

Hui Zheng; Paola Echave

Disclosures

Am J Epidemiol. 2021;190(11):2242-2255. 

In This Article

Abstract and Introduction

Abstract

Morbidity and mortality have been increasing among middle-aged and young-old Americans since the turn of the century. We investigated whether these unfavorable trends extend to younger cohorts and their underlying physiological, psychological, and behavioral mechanisms. Applying generalized linear mixed-effects models to data from 62,833 adults from the National Health and Nutrition Examination Surveys (1988–2016) and 625,221 adults from the National Health Interview Surveys (1997–2018), we found that for all sex and racial groups, physiological dysregulation has increased continuously from Baby Boomers through late-Generation X and Generation Y. The magnitude of the increase was higher for White men than for other groups, while Black men had a steepest increase in low urinary albumin (a marker of chronic inflammation). In addition, Whites underwent distinctive increases in anxiety, depression, and heavy drinking, and they had a higher level than Blacks and Hispanics of smoking and drug use in recent cohorts. Smoking is not responsible for the increasing physiological dysregulation across cohorts. The obesity epidemic contributes to the increase in metabolic syndrome but not in low urinary albumin. The worsening physiological and mental health profiles among younger generations imply a challenging morbidity and mortality prospect for the United States, one that might be particularly inauspicious for Whites.

Introduction

Around the turn of the century, Americans' population health seemed to start declining. After decades of improvement in functioning and a decline in disability among the US population aged 65 or older,[1–9] newer cohorts approaching middle-age (ages 40–59) and "young old" (ages 60–69) began to experience increasing functional limitations and disability[10–14] starting in the late 1990s. The worsening disability trend is accompanied by increasing mortality rates in middle age around the early 2000s, which were thought to be driven by rising "deaths of despair" (drug-, alcohol-, and suicide-related mortality) combined with slowdowns in progress in heart disease mortality.[15,16] Suicide, cirrhosis of the liver, and fatal drug overdoses suggest that victims are likely suffering from psychological distress.[16] The rising mortality rate narrative was initially only applied to the White population. Later research, however, suggests it is not just a White problem.[17,18]

The literature portrays an alarming picture of American's health, but several gaps still remain. First, studies only look at the end of the morbidity process, which begins for populations with the physiological dysregulation (PD) indicated by a number of biological risk factors and followed by subsequent diagnosis of diseases, functioning loss, disability, frailty, and death.[19] Mental illness (e.g., anxiety and depression) and health behaviors also precede the onset of disability and mortality. Therefore, it is essential to investigate whether the unfavorable trend in morbidity and mortality in recent decades should be attributed to health behavior changes driven by psychological distress,[16] deterioration of innate physiological functioning, or both.

Second, these aforementioned studies are period-based and focus on older people, among whom disability, functioning loss, or death is more common. Even fewer studies have examined young people, outside of a few notable exceptions.[20,21] An approach that incorporates younger cohorts into the study of physiological status, mental health, and health behaviors could reveal whether the unfavorable trend has been continuing into younger generations, which could elucidate the future trend of morbidity, disability, and mortality when these younger generations reach older ages, when disability and death are more common. Third, research has reported divergent trends in morbidity and mortality over time periods or across birth cohorts by race and sex.[16,18] It deserves further examination whether these divergent trends are shaped by racial/ethnic and sex disparities in the intercohort physiological, psychological, or behavioral patterns.

To address these gaps, we undertook a comprehensive investigation of the trends of physiological status, mental health, and health behaviors by race and sex across a century of birth cohorts from the Greatest Generation to Generation Y. We further conducted a preliminary investigation on the role of smoking and obesity in the cohort trend of physiological status. These analyses can uncover underlying physiological, psychological, and behavioral mechanisms shaping the unfavorable trend in morbidity and mortality in the recent decades, reveal sex and racial disparities, and shed light on the prospects for Americans' health in the coming decades.

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