Elsevier

Social Science & Medicine

Volume 62, Issue 4, February 2006, Pages 923-940
Social Science & Medicine

A socially neutral disease? Individual social class, household wealth and mortality from Spanish influenza in two socially contrasting parishes in Kristiania 1918–19

https://doi.org/10.1016/j.socscimed.2005.06.051Get rights and content

Abstract

The Spanish influenza pandemic of 1918–19 was one of the most devastating diseases in history, killing perhaps as many as 50–100 million people worldwide. Much of the literature since 1918 has favored the view that mortality from Spanish influenza was class neutral. This view has prevailed, even though several contemporary surveys showed that there indeed were clear differences between the classes in disease incidence and that case fatality rates from influenza and pneumonia also varied according to socioeconomic status. Furthermore, studies of more recent influenza epidemics have also shown that there can be clear class differentials in mortality in this type of illness—is there any reason to believe that Spanish influenza was different? This paper is the first study in which individual- and household-level data which are unique for the period are utilized to test the conservative hypothesis that Spanish influenza was a socially neutral disease with respect to mortality. Through the use of Cox regressions in an analysis of two socially contrasting parishes in the Norwegian capital city of Kristiania, it is shown that apartment size as an indicator of wealth of a household, in addition to social status of place of residence, were the only socioeconomic variables that had an independent and significant effect on mortality after controlling for age, sex and marital status.

Introduction

Socioeconomic differences between classes as a factor in the incidence of disease, mortality and survival have been documented for different time periods in all countries for which data exists (Feinstein, 1993; Kunst & Mackenbach, 1994). These kinds of differences have been documented for a number of causes of illness and death, including cardiovascular diseases (Vallin, Meslé, & Valkonen, 2001), several types of cancer (Kravdal, 2003), chronic obstructive pulmonary disease (Prescott & Vestbo, 1999), and mortality associated with excessive alcohol consumption (Mäkelä, Valkonen, & Martelin, 1997). There is also ample evidence that there were distinct differences between the social classes with respect to the main causes of death in historical populations, particularly for tuberculosis and cholera fatalities (e.g. Gjestland & Moen, 1988; Hansen, 1985).

This paper addresses the general question whether a social gradient is also prevalent in mortality from influenza in annual epidemics. In particular, it examines the role of socioeconomic status, both of individuals, households and neighborhoods, in explaining the variance in mortality associated with the Spanish influenza pandemic which may have killed 50–100 million worldwide in 1918–19 (Johnson & Mueller, 2002). Indeed, socioeconomic differentials have also been reported for influenza and pneumonia combined, not only in the risk of dying (Kitagawa & Hauser (1968), Kitagawa & Hauser (1973); Regidor, Calle, Navarro, & Domínguez, 2003; Singh & Siahpush, 2001), but also in the actual risk of contracting influenza (Dutton, 1988; Glezen, Paredes, & Taber, 1980). Moreover, the socioeconomic differences in mortality from influenza and pneumonia found in these studies, which include the United States in 1950, 1960 and the period 1979–89, and Spain in 1996–97, were among the greatest compared to any other cause of death. However, only a very few studies have been specifically directed towards explaining the social profile of these two causes of death. When examining the data from these relatively recent influenza epidemics, can there be any reason to doubt that the lower socioeconomic classes had a higher mortality from influenza and pneumonia than the higher classes during the pandemic in 1918?

House-to-house surveys conducted in the United States and Norway in 1918–19 showed that there were marked social differences in both the incidence and lethality from Spanish influenza (Britten, 1932; Collins, 1931; Hanssen, 1923; Sydenstricker, 1931; Vaughan, 1921), while a similar study of four cities in England found no clear relationship between incidence and/or case fatality rates and social status (Great Britain Ministry of Health, 1920). Debate has continued in the literature ever since 1918 over whether social status played any role in mortality from the 1918–19 pandemic; most studies contend that it was socially neutral. Proponents of the “socially neutral” view claim that Spanish influenza struck blindly and randomly because the pandemic introduced a new virus that few, if any, had the immunity to fight. They argue that Spanish influenza differed to annual epidemics in which a large part of the population has acquired immunity from exposure to previous epidemics (Brainerd & Siegler, 2003; Crosby, 2003; Rice, 1988; Stevenson, 1921; Tomkins, 1992; van Hartesveldt, 1992; Winter & Robert, 1997). A second argument commonly used to support this view is the fact that in 1918, the largest relative increase in death rates all over the world was among people between the age of 20 and 40 years as opposed to the very young and the elderly as is normally seen during annual influenza epidemics. However, many previous studies did not carry out a careful statistical investigation of the association between mortality and socioeconomic status themselves. They tended instead to rely upon anecdotal evidence from physicians of the time, using this to support the argument that Spanish influenza was a “classless” disease because the odds of survivability seemed to favor the most robust and previously healthy of those aged 20–40 years. The argument was made that even kings and presidents were laid low by influenza. A possible explanation for this view having prevailed in the literature may be that too little distinction has been made between the risk of being infected by influenza on the one hand (“everybody gets it”), and the risk of actually dying from influenza or pneumonia. In the first instance, the risk of contracting the disease may be only moderately associated with socioeconomic status, while several studies have shown that there was a strong connection between mortality from the disease and socioeconomic status. On the other hand, some scholars argue that like tuberculosis and cholera, Spanish influenza claimed higher death rates amongst the destitute and most poorly situated than among the wealthy and privileged (Hersch (1920), Hersch (1932); Johnson, 2001; Mamelund, 2003b; McCracken & Curson, 2003; Sydenstricker, 1931; Zylberman, 2003). Supporters of this view admit that the virus itself may have had certain attack properties that were independent of social class. However, it would appear that there indeed were clear social differences in a person's chance of surviving the disease.

Most of the previous studies on socioeconomic status and mortality from the 1918–19 pandemic have been univariate and descriptive in type. The contributions from them therefore fail to demonstrate the independent effects on Spanish influenza mortality of age, sex, socioeconomic class, crowding, ethnicity, spatial diffusion, climate, and other geographical variables. Recent exceptions to this pattern in the nature of the studies are the cross-sectional studies of the United States (Brainerd & Siegler, 2003) and England and Wales (Johnson, 2001), who, respectively, found no and only weak indications of class differentials in mortality. Studies of Sydney, Australia (McCracken & Curson, 2003), and Norway (Mamelund, 2003b) on the other hand could report a significant social gradient in mortality. However, because the associations in these studies were not estimated using individual-level data, no definitive conclusion could be drawn as to whether or not there were any causal links between these variables.

This paper is the first to apply Cox proportional hazard models combined with “state of the art” data for the period on the level of individuals, households, and parish, to contest the conservative assumption that Spanish influenza was a socially neutral disease with respect to mortality. No earlier study on the subject has ever included data on different levels of aggregation in the same model to search for the causes of variation in Spanish influenza mortality. The paper uses mortality and census data from two intentionally selected socially contrasting parishes in the Norwegian capital of Kristiania (renamed Oslo in 1924), namely Frogner and Grønland-Wexels. The nominal censuses for 1918 and 1919 used here allow a very close follow-up of individuals from the start of the pandemic in the early spring of 1918 through to the end of it in the winter of 1919. Finally, registration of deaths and the carrying out of the censuses were on the whole undisturbed by the First World War, as Norway was a neutral country. Such data are seldom available for the belligerent countries. Existing data from such countries are usually unreliable because of gaps in registration and because it is difficult to separate deaths from the pandemic from direct or indirect deaths caused by the war.

Section snippets

Parishes

There are two reasons for limiting the analysis to the two parishes of Frogner and Grønland-Wexels, which are comparable in size and tally together 41,000 individuals or 16 per cent of a total population in Kristiania of 260,000 on 1 February 1918 (Wexels was merged with Grønland in 1919). First, significant differences in all-cause mortality as well as cause-specific mortality have already been shown to exist between the traditionally poor, high-mortality parishes to the east of the city and

Method of analysis

The analysis consists of two parts. The first part is descriptive, and examines the correlation between mortality from Spanish influenza and indices of deprivation and wealth in the city of Kristiania as a whole, with special focus on the contrast between Grønland-Wexels and Frogner. In the second part of the analysis, the effects of the covariates described above upon those surviving Spanish influenza are estimated using Cox proportional hazards models. The hazard rate for the individual i

Descriptive analysis of the whole capital city of Kristiania

The first cases of influenza associated with Spanish influenza in Norway were reported in the first week of April 1918. However, the first scattered cases of influenza in Kristiania, which later proved to be the smoldering of a pandemic wave, occurred on 15 June 1918 (Mamelund, 1998). It was not until the first half of July that the reported disease incidences of influenza began to skyrocket, taking the dimensions of a pandemic wave. Fig. 1 clearly shows a second outbreak of Spanish influenza

Effects of individual social class and household wealth on mortality

One of the main findings in this analysis is that mortality from Spanish influenza was 19–25 per cent lower among the two upper classes compared to the working class when all other factors were the same (model 3). This relationship between mortality and social class was not statistically significant, but nevertheless in accordance with the hypothesis. Furthermore, when using apartment size as a proxy for household income, it was found that size of apartment had a negative effect on mortality.

Conclusion

Debate has continued in the literature ever since 1918 over whether there were socioeconomic differences in mortality from the 1918–19 pandemic, with massive support for the view that it was socially neutral. Cox proportional hazard models and unique data at the level of individuals and households combined with a control for place of residence are used for the very first time in this paper to ascertain whether there were differences in mortality from Spanish influenza with respect to individual

Acknowledgments

I am most grateful to Sølvi Sogner, Nico Keilman, Øystein Kravdal, Anders Barstad, and Hans Henrik Bull for their helpful comments to the paper. My thanks also go to the staff of Oslo City Archives, who were helpful in localizing the data applied in this paper, and for providing my research assistant Kirsti Hansen with excellent working conditions while making copies of the data. Furthermore, the staff at the Norwegian Historical Data Center at the University of Tromsø and Bardufoss rendered

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