Researchers here look at differences in life expectancy by income over the period of time in which obesity emerged to became a major issue. Recall that income, wealth, status, education, intelligence, and life expectancy all tend to correlate with one another, and identifying the arrow of causation is a challenge. Researchers found that the difference in life expectancy between high income and low income segments of the population has widened over the past 60 years. The glass half full viewpoint is that this is because people with higher incomes are undertaking more effective means of maintaining long term health. The glass half empty view is that obesity is very damaging to health and longevity, and people with lower incomes become obese to a greater degree than those with higher incomes.
This study examines the long-term association between income and life expectancy in Sweden between 1960 and 2021. The study is based on register data that include all Swedish permanent residents aged 40 years and older. The results show that the gap in life expectancy between the top and bottom income percentiles widened substantially: For men, it increased from 3.5 years in the 1960s to 10.9 years by the 2010s, and for women, from 3.8 years in the 1970s to 8.6 years by the 2010s. Despite a reduction in income inequality and an expansion of social spending from the 1960s to the 1990s, health inequality continuously increased over the period under study.
The changes of the relation between real income and life expectancy, the so-called Preston curve, reveal a much faster improvement in life expectancy in the upper half of the income distribution than suggested by the cross-sectional relation between income and life expectancy. Analysis of causes of death identified cardiovascular diseases as the main contributor to improved longevity, while cancer contributed more to the increased gap in life expectancy for women and equally for men. Finally, analysis of the change in the income gradient in avoidable causes of death showed the strongest contribution of preventable causes, both for men and women.
This study reveals that the income gradient in life expectancy in Sweden has steadily increased since the 1960s, despite a reduction in income inequality until 1990. This challenges the "absolute income hypothesis" - the notion that economic resources per se affect life expectancy and that increasing income inequality directly drives health disparities. Instead, a "third factor" appears to be associated with both income and life expectancy, leading to greater gains in life expectancy among higher income groups. These gains are evident in both preventable and treatable disease mortality and appear more strongly for preventable causes, suggesting that higher-income individuals are more rapidly adopting healthier lifestyles. This finding highlights the need to consider factors beyond economic resources in addressing health inequalities.
Link: https://doi.org/10.1073/pnas.2418145122
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