The researchers used data from the Midlife in the United States (MIDUS) project, a longitudinal study on aging. Using data from the first collection wave in 1994-1996 through a censor date of 2018, the researchers used survival models to analyze the association between net worth and longevity.
To tease apart factors of genetics and wealth, the full sample was segmented into subsets of siblings and twins.
In the full sample of 5,400 adults, higher net worth was associated with lower mortality risk. Within the data set of siblings and twin pairs (n=2,490), they discovered a similar association with a tendency for the sibling or twin with more wealth to live longer than their co-sibling/twin with less. This finding suggests the wealth-longevity connection may be causal, and isn’t simply a reflection of heritable traits or early experiences that cluster in families.
“The within-family association provides strong evidence that an association between wealth accumulation and life expectancy exists, because comparing siblings within the same family to each other controls for all of the life experience and biology that they share,” said corresponding author Eric Finegood, a postdoctoral fellow in the Institute for Policy Research at Northwestern.
The researchers also considered the possibility that previous health conditions, such as heart disease or cancer, could impact an individual’s ability to accrue wealth due to activity limitations or healthcare costs — possibly confounding any association between wealth and longevity. To address this, they re-analyzed the data using only individuals without cancer or heart disease. However, even within this sub-group of healthy individuals, the within-family association between wealth and longevity remained.
The study’s senior author is Greg Miller, the Louis W. Menk Professor of Psychology and faculty fellow at the Institute for Policy Research at Northwestern. Co-authors of the study include other Northwestern faculty and trainees (Edith Chen, Daniel Mroczek, Alexa Freedman) as well as researchers from the University of Illinois, Urbana-Champaign; West Virginia University; Purdue University; and the University of Minnesota.
“Far too many American families are living paycheck to paycheck with little to no financial savings to draw on in times of need, said Miller. “At the same time, wealth inequality has skyrocketed. Our results suggest that building wealth is important for health at the individual level, even after accounting for where one starts out in life. So, from a public health perspective, policies that support and protect individuals’ ability to achieve financial security are needed.”
