Insight on 'typical' longevity: An analysis of the modal lifespan by leading causes of death in Canada

Abstract

(ProQuest: ... denotes formulae omitted.)1.IntroductionThe spectacular longevity gains achieved by low mortality countries in the last two centuries are the direct consequence of ongoing progress in fighting a wide variety of diseases. During the first half of the 1900s, advances in immunization, sanitation, and nutrition led to the near-eradication of major infectious and parasitic diseases, as well as maternal, perinatal, and nutritional disorders (Horiuchi 1999, Omran 1971, Preston 1976). Throughout this period, life expectancy at birth increased steadily and very rapidly, reaching a level of about 65-70 years old for both sexes combined by the mid20th century (Human Mortality Database). As fewer individuals succumbed to these diseases in the early years of life and increasingly survived to older ages, the risk of developing chronic degenerative diseases became more likely. By the early 1950s these age-associated conditions replaced infectious diseases as the most common cause of death in industrialized societies. After the fall of mortality at young and middle ages to historically low levels, gains in life expectancy at birth slowed down for about ten years, leading some demographers to argue that mortality improvements were no longer possible.However, the late 1960s ushered in a new of progress characterized by the decline of chronic degenerative diseases, particularly cardiovascular diseases. Kannisto (2001) referred to an era of delayed aging, as mortality at older ages dropped faster than at younger ages and deaths above age 80 started to decline considerably for the first time (Kannisto et al. 1994). Thereafter, advances in the extension of human life were mainly fuelled by improvements in old-age survival (Mesle and Vallin 2006, Wilmoth et al. 2000). Consequently, the upturn in life expectancy at birth resumed but the pace of increase was slower during this new than in preceding years.Recent evidence suggests that life expectancy at birth underestimates progress made in longevity extension when such progress is principally driven by improvements in the survival of the elderly (Canudas-Romo 2010, Kannisto 2001). Therefore, life expectancy at some middle or early old ages, such as 50 or 65, takes center stage in analyses monitoring old-age survival. One of the main disadvantages of these lifespan measures, however, is their dependence on an arbitrary selection of the age limit, and hence on an arbitrary definition of 'old' (Kannisto 2001). The conditionality upon survival to an age threshold constitutes another important disadvantage, as it reflects the average length of life still to be lived by the most robust individuals.To make up for these shortcomings, Kannisto (2001), building on earlier work by Quetelet (1835) and Lexis (1877, 1878), proposed the late modal age at death (M) as a promising lifespan indicator in an where the extension of human life is primarily due to the reduction of old-age mortality. Under a given mortality regime, this measure represents the most common (i.e., most frequent) or 'typical' length of life among adults. In the early years of its introduction to contemporary demography the attractiveness of M was its freedom from any arbitrary age limit. More recently, studies have also demonstrated that the late mode is solely determined by old-age survival and that the pattern of trends and differentials in M can differ greatly from those in life expectancy, at birth, or at some early old age (Canudas-Romo 2010, Cheung et al. 2009, Horiuchi et al. 2013, Office of National Statistics 2012). Therefore, a growing number of researchers have been monitoring longevity gains in low mortality countries through the lens of the late modal age at death (Brown et al. 2012, Canudas-Romo 2008, Cheung and Robine 2007, Cheung et al. 2005, 2009, Cheung, Robine, and Caselli 2008, Kannisto 2007, Ouellette and Bourbeau 2011, Ouellette, Bourbeau, and Camarda 2012, Robine 2001, Thatcher et al. …