Trends in prevalence, mortality, and risk factors of dementia among the oldest-old adults in the United States: the role of the obesity epidemic

Abstract

The oldest-old population, those aged ≥ 80 years, is the fastest-growing group in the United States (US), grappling with an increasingly heavy burden of dementia. We aimed to dissect the trends in dementia prevalence, mortality, and risk factors, and predict future levels among this demographic. Leveraging data from the Global Burden of Disease Study 2019, we examined the trends in dementia prevalence, mortality, and risk factors (with a particular focus on body mass index, BMI) for US oldest-old adults. Through decomposition analysis, we identified key population-level contributors to these trends. Predictive modeling was employed to estimate future prevalence and mortality levels over the next decade. Between 1990 and 2019, the number of dementia cases and deaths among the oldest-old in the US increased by approximately 1.37 million and 60,000 respectively. The population growth and aging were highlighted as the primary drivers of this increase. High BMI emerged as a growing risk factor. Females showed a disproportionately higher dementia burden, characterized by a unique risk factor profile, including BMI. Predictions for 2030 anticipate nearly 4 million dementia cases and 160,000 related deaths, with a marked increase in prevalence and mortality anticipated among those aged 80-89. The past 30 years have witnessed a notable rise in both the prevalence and mortality of dementia among the oldest-old in the US, accompanied by a significant shift in risk factors, with obesity taking a forefront position. Targeted age and sex-specific public health strategies that address obesity control are needed to mitigate the dementia burden effectively.

Keywords: Body mass index; Dementia; Mortality; Prevalence; Public health.

Fig. 1

Trends of prevalence and mortality among US oldest-old adults with dementia in the four age groups from 1990 to 2019. A Trend of absolute number of prevalent cases. B Trend of prevalence rates (per 100,000). C Trend of mortality numbers. D Trend of mortality rates (per 100,000)

Fig. 2

Decomposition analyses on changes in dementia prevalence and mortality and contributions of population-level determinants among US oldest-old adults. A Absolute changes of prevalence attributed to the three factors. B Contribution proportions in changes of prevalence attributed to the three factors. C Absolute changes of mortality attributed to the three factors. D Contribution proportions in changes of mortality attributed to the three factors. The black dot in A and C represented the combined effect of all three factor, including aging, population growth, and epidemiological change

Fig. 3

PAFs and attributable numbers of dementia mortality due to risk factors among US oldest-old males and females in the four age groups from 1990 to 2019. A PAFs of dementia mortality due to risk factors. B Attributable numbers of dementia mortality due to risk factors. PAF = population-attributable fractions

Fig. 4

Predicted prevalence and mortality of US oldest-old adults with dementia in the four age groups from 2020 to 2030. A Predicted absolute number of prevalent cases. B Predicted prevalence rate (per 100,000). C Predicted mortality numbers. D Predicted mortality rate (per 100,000)