The Risk of Being Sick: Mortality Trends in Four Countries
Citation: Riley (1990) The Risk of Being Sick: Mortality Trends in Four Countries.
Although mortality rates in developed countries have been declining for more than a century, recent health surveys in a number of countries suggest that morbidity may be worsening. Interpreting morbidity trends depends on whether incidence (i.e., the risk of getting sick) or duration dependent prevalence (i.e., the risk of being sick over a certain span of time) is examined. Riley argues that prevalence is a more useful measure because it reflects the burden of illness and disability in a society, which has implications for the economy and health care system. In this article, Riley reviews evidence on morbidity and mortality trends in four countries (Japan, US, Britain and Hungary). Previous research often adopted the assumption of "parallelism," which means that improving mortality trends imply improving morbidity trends. But Riley questions this assumption. "If more people survive at given ages, it is apparent that they have avoided some of the hazards that caused death in previous periods. But it is not apparent whether they avoided ill health or whether they merely avoided death" (p. 406). Moreover, the epidemiological transition implies that illnesses will become more protracted, since short-lived but fatal infectious illnesses are replaced by chronic diseases that may cause death only after a prolonged period of ill health. Data from Japan, Britain and the US all show the same phenomenon. Mortality and morbidity rates are inversely related, with the former declining and the latter increasing. Hungary, which experienced a mortality increase in the mid-1960s, also exhibits the inverse relationship, but with decreasing morbidity. In the US, the age-specific incidence of acute conditions remained about the same over the period 1962-1986, but the risk of being sick increased since average durations of ill-health increased.
Despite evidence to the contrary, some "optimists" (e.g., Fries) maintain that since mortality is occurring at later ages, the onset of potentially fatal illnesses and injuries has been deferred. Such a view is sometimes referred to as the "compression of morbidity". But "pessimists" counter with (1) an epidemiological argument that chronic illnesses have become more prevalent precisely because of progress made in prolonging life through early detection and management of diseases and (2) a statistical argument which points to a positive gradient in the prevalence sickness trends. In short, although the overall risk of falling sick may have diminished over the past century, the risk of being sick has increased due to increased life expectancy, the substitution of infectious diseases with chronic conditions, and improved detection and treatment of "manageable" but non-curable chronic conditions (e.g., diabetes and heart disease).
While the pessimistic view may be correct, Riley does not approve of the negative connotation. "To a substantial degree more protracted sickness constitutes an achievement, because it is a byproduct of objectives that humankind set for itself. But this is an interim achievement, one that compels us to reformulate our objectives by designing policies that will reduce sickness time without allowing mortality to increase" (p. 428).