Continuing the Search for Determinants of Healthy Life Span and Longevity
Life expectancy in humans worldwide has been experiencing dramatic increases for the past two centuries (Oeppen and Vaupel 2002). In most countries, the extension of lifespan is associated with a transition from a long historical period of high fertility and high mortality (particularly infant mortality (Singh and Yu 1995)) to low fertility and low mortality. This demographic trend leads to rapidly growing populations of the elderly (e.g., the United Nations projects a nearly twofold increase in the proportion of the 60+ population from about 10–21 % over the next five decades (UN 2007)) which raises serious concerns about a possible accompanying expansion of morbidity and disability, especially in developed countries (Olshansky et al. 2007; Robine 2003; Sierra et al. 2009). Because morbidity is in a causative pathway to disability (Verbrugge and Jette 1994), reducing the burden of morbidity could lead to compression of years of unhealthy life.
