The fungibility of human longevity, Charlotte Paul

The Healthy Country? A History of Life and Death in New Zealand
Alistair Woodward and Tony Blakely
Auckland University Press, $50.00,
ISBN 9781869408138

Non-Māori New Zealanders lived longer than any other peoples on earth between 1876 and 1940. Figuring out why is the starting point for this fascinating and scholarly study. Of course, even this statement begs a question. These figures apply to only a segment, not the total population of New Zealand, yet the comparisons are generally with total populations of other countries. Nevertheless, the non-Māori life expectancy was far ahead, and this was the only data available until 1913 (when Māori deaths were first collected). Moreover, epidemiologists Woodward and Blakely are properly even-handed and comprehensive in investigating both Māori and non-Māori life expectancy from pre-contact until 2011.

Life expectancy tells you the average number of years a child, born in a given year, is expected to live. It is generally calculated using current mortality rates for every age group (period life expectancy). This will not be the same as the actual average length of life for someone born in a given year if mortality rates are changing. If they are falling over time, life expectancy will be an underestimate. Sometimes life expectancy is misinterpreted and taken as a measure of life span. But low life expectancies generally reflect very high death rates in infancy and childhood; those who survive childhood could expect to live considerably longer.

How do we think about reasons for changes in life expectancy, or reasons for differences among countries? Some commentators believe that single factors such as economic growth or the amount of income inequality in a country can explain such differences. Woodward and Blakely are more cautious. With admirable attention to “particular realities”, they discuss the evidence that specific factors were important at different times and for different groups.

Their first reason for the exceptional long life enjoyed by non-Māori (1860 to 1940) was that the largely migrant population was healthier than the average in the countries they came from (the healthy migrant effect). Second, the physical environment provided the conditions for protein- and calorie-rich food production, and it did not have the city and household crowding or the polluting industries of Europe. Third, there was an early and rapid fertility decline. Smaller family size has marked effects on infant and child survival.

Māori did not fare well at first contact from the introduction of new infectious diseases, reducing both life expectancy and birth rates. Moreover, the loss of land played a part – even if not a direct one – in their reduced life expectancy, just as the gaining of productive land increased life expectancy of non-Māori. This is a repeated theme: that the gain in life expectancy by one group might come at the cost of loss of years of life by another.

Māori life expectancy started to increase again before 1900. The reasons are speculative, but the authors make a careful case for the importance of adaptation to infectious diseases, take-up of modern health practices, access to more effective health care, and improvements in living conditions. From 1940 to 1980, Māori life expectancy increased much faster than non-Māori. Amongst Māori, death rates fell at every age, but most strongly amongst infants and children. In contrast, amongst non-Māori aged 45 and over there was almost no decline in mortality. This was the period in which New Zealand experienced an epidemic of deaths due to coronary heart disease. The authors emphasise the roles of smoking, saturated fat and cholesterol. It was a time of cheap beef and high butter consumption and low consumption of vegetable oils.

From 1980, there was again a divergence in life expectancy between Māori and non-Māori, up to 1996, followed by a convergence. This time the authors highlight the burden on many Māori of the social and economic reforms of Roger Douglas and Ruth Richardson. Māori unemployment rose, suicide rates rose. Here again, they suggest that non-Māori benefited from the structural reforms, while Māori bore the social costs. In this period, medical care and public health interventions were also very important.

Woodward and Blakely draw on the work of other scholars, especially demographer Ian Pool, but make a substantial contribution themselves, though their “heavy machinery” of demography and epidemiology could sometimes be wielded with a lighter touch. Graphs are complicated, often hard to decipher (fine lines and minute gradations of grey), and contain a few errors. There are some points on which experts will disagree, but their thoroughness and their ability to synthesise information from a wide range of sources are impressive.

How should we think about how the “organised efforts of society to improve health” work? Woodward and Blakely propose a metaphor that fits their personae as optimistic cyclists. It is “a track on which society walks (or bicycles) to good health”. Society clears away obstacles and helps keep up the track, ensuring “well-defined edges, a low friction surface and a helpful gradient”. Why does this metaphor make me uneasy? I think many of us trudge along the road of life not on a quest for health, but to make a meaningful life and some contribution to the common weal. Health and longer time on earth help, but they are not the purpose of life. Moreover, for populations, economic growth rather than health sets the direction of travel. Epidemiologist John Powles describes how each stage of economic development has brought favourable and adverse effects for health. These adverse effects are painstakingly discovered and then countered by public health measures. The recent paradigm case is the ease of travel and the closeness of peoples that allowed HIV to spread around the world, partly countered by putting that thinnest of barriers, the condom, between people. Ebola has shown how, without good public health systems, such adverse effects can overwhelm a country.

This makes sense of why public health workers keep offending people in new ways; always calling for new interventions in society. These days it is particularly obesity and alcohol. The obesity epidemic is caused by economic development and Woodward and Blakely are good and straightforward on the reasons and what is needed to control it. Some scholars predict that increasing rates of obesity, if unchecked, may actually decrease life expectancy in the United States.

In contrast, Woodward and Blakely are optimistic that the obesity epidemic will have less effect and that life expectancy will continue to increase. Moreover, though they acknowledge concerns about increasing disability and dementia at older ages, they point out that, relatively, we are not spending more of our whole lives disabled and that rates of dementia may be slowing in more recent generations. They discuss ecological threats and climate change and what we owe future generations, but none seriously dent their optimism.

Part of the reason for their optimism is that “best” life expectancy has improved in a linear fashion since 1840 and shows no signs of slowing down. But they may be wrong to rely so much on this analysis by Oeppen and Voupel (which included the New Zealand data that sparked their interest initially). A more detailed investigation (by Vallin and Meslé) concluded that the New Zealand data should be removed entirely. Their justification was that analyses of second-best countries showed New Zealand was an outlier, especially in the earlier years. The authors ascribed this to its “singular population history” with a majority of immigrants who “were strongly selected by the difficulties of acquiring the means to emigrate from Europe and surviving the long voyage”. When this was done, improvement in “best” life expectancy becomes non-linear: a shallower slope to 1885, a steeper slope to 1960, and a slowing since then.

This more muted interpretation, in which new threats to longevity are expected, and the rate of increase is already slowing, is still consistent with Woodward and Blakely’s prescriptions for the future. Human longevity, they say, is “fungible”: the conditions necessary for low mortality if used for this are not available elsewhere. Fungible is an odd term here, but the concepts of costs and transfers are important. Non-Māori health improved early on at the expense of Māori. Now good conditions in old age are arguably at the expense of children. Woodward and Blakely sensibly say that the age of superannuation must be raised and ways found to allow those who can no longer work to get it earlier. If Piketty is right, unfettered capitalism tends inexorably towards increasing inequality. They could have gone further and argued more strongly for the redistribution of resources.

Charlotte Paul is Emeritus Professor of Preventive and Social Medicine at the University of Otago.

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Posted in Health, History, Non-fiction, Review and Sociology
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