The point you're referring to relates specifically to geographic differences.

From the results section: "inequality in life expectancy increased over time. Between 2001 and 2014, life expectancy increased by 2.34 years for men and 2.91 years for women in the top 5% of the income distribution, but by only 0.32 years for men and 0.04 years for women in the bottom 5% (P < .001 for the differences for both sexes)."

So I think the co-authors had a point when they talked about retirement age!