The Longevity-Frailty Hypothesis: Evidence from COVID-19 Death Rates in Europe

Sammy Zahran; Levi Altringer; Ashok Prasad

COVID-19 disproportionately afflicts the elderly, especially the elderly with underlying health conditions. Frailty is a term used to capture a range of age-related conditions that impair the elderly. Frail populations are prone to dependency, and less likely to withstand a health shock (Hoogendijk et al, 2019; Theou et al 2018 , Vetrano et al, 2018 Denfeld et al, 2017) . The share of population ≥ 65 years of age is an imperfect proxy for elderly survival and consequent frailty because it is confounded by other components of population size and mortality selection. Among many other examples, the numerator in the share of population ≥ 65 partly reflects elderly survival but may also reflect the parental fertility of the present elderly relative to the fertility of subsequent cohorts. With respect to mortality selection, frail populations are less resistant to health shocks, decreasing their survival probability. At a population level, this results in a relative increase of death resistant or health robust individuals with age (Vogt and Missov 2017; Vaupel et al, 1979) . Consider two similarly economically developed countries with varying survival to age of 75, the standard threshold for premature death. Suppose that one country has high and the other low risk of premature death from all causes. Other things held equal, persons surviving to 75 in the high-risk all-cause mortality country are more positively selected on the underlying ability to death resist than counterparts in the low-risk all-cause mortality country. Given mortality selection, elderly persons over the age of 75 in the high-risk country are more likely to withstand adverse health shocks than similarly aged persons in the low-risk country because they are different on the unobserved trait of underlying frailty.