Population health in transition.

Until recent times most deaths were caused by infectious diseases, diseases, or violence. Let us ignore violent deaths, as they can occur at any age. Infectious are a threat from day of birth and, indeed, very young are most susceptible to their attack. People die of at older ages because it usually takes time for body to degenerate and there is little else to die from, though they must eventually die of something. What happened in mortality transition was conquest of infectious disease, not a mysterious displacement of infection by degeneration as cause of death. The resulting demographic transition with its changing age of death and existence of large numbers of people afflicted with chronic disease (rather than life-threatening infectious disease) is important for planning health services and medical training, which is current focus of burden of disease approach. Why did Abdel Omran's essay (1) have such an impact on public health community, an impact with echoes of Malthus's views on population? There are certain similarities to The First Essay of Malthus in 1798: Omran firmly stated a number of propositions, which were only sparingly spelled out and buttressed by limited references. Also, he republished paper several times although, unlike Malthus, his additions were largely limited to applying thesis to United States and suggesting a fourth stage (2). Omran postulated displacement of pandemics by degenerative and man-made diseases without explaining what was meant by latter, but in 1982 he specified it included radiation injury mental illness, drug dependency, traffic accidents, occupational hazards (2). The public health community was undoubtedly attracted by prospect of combating man-made diseases: what human activity could create, human activity could correct. The other attraction was suggestion somehow and man-made had replaced infectious ones, which presented, a picture of combat between warring camps of disease into which health professionals could throw themselves. Omran did in places relate this replacement to mortality decline and changing age structures, though he touched upon age structure only very lightly and usually treated a population as an undifferentiated unit. This approach was central in giving paper such force. Omran added strength to his argument by segmenting epidemiological transition into periods with different mortality and disease levels. Thomas McKeown also did this, though only his first two historical papers (3, 4) were published before Omran's. The other form of segmentation Omran used was numbered propositions, to which we now turn. Proposition One, that mortality is a fundamental factor in population dynamics, has always been agreed: in all demographic transition theories it is prior decline in mortality in due course precipitates fertility decline. It is true for decades after Second World War demographers gave more attention to causes and nature of fertility decline than to those of mortality decline, though they stressed such attention was necessary because of preceding unforeseen steep mortality decline in developing countries. The importance of Omran's and McKeown's work is they drew attention to this imbalance. The core of Proposition Two, During transition, a long-term shift occurs in mortality and disease patterns is clear, but subsequent excursion into determinants of transition is subject to same criticisms as have been levelled at McKeown's work. The ascription of 19th-century Western mortality decline primarily to ecobiological and socioeconomic factors (McKeown said nutrition), argument the influence of medical factors was largely inadvertent, and implication struggle against infectious disease was unimportant after turn of century, are all contestable. …