The 1918 influenza pandemic did not accelerate tuberculosis mortality decline in early‐20th century Newfoundland: Investigating historical and social explanations

Abstract

Objectives: The selective mortality hypothesis of tuberculosis after the 1918 influenza pandemic, laid out by Noymer and colleagues, suggests that acute exposure or pre-existing infection with tuberculosis (TB) increased the probability of pneumonia and influenza (P&I) mortality during the 1918 influenza pandemic, leading to a hastened decline of TB mortality in post-pandemic years. This study describes cultural determinants of the post-pandemic TB mortality patterns in Newfoundland and evaluates whether there is support for this observation. Materials and methods: Death records and historical documents from the ProvincialArchives of Newfoundland and Labrador were used to calculate age-standardized island-wide and sex-based TB mortality, as well as region-level TB mortality, for 1900-1939. The Joinpoint Regression Program (version 4.8.0.1) was used to estimate statistically significant changes in mortality rates.Results: Island-wide, females had consistently higher TB mortality for the duration of the study period and a significant shift to lower TB mortality beginning in 1928.There was no similar predicted significant decline for males. On the regional level, no models predicted a significant decline after the 1918 influenza pandemic, except for the West, where significant decline was predicted in the late-1930s. Discussion: Although there was no significant decline in TB mortality observed immediately post-pandemic, as has been shown for other Western nations, the female post-pandemic pattern suggests a decline much later. The general lack of significant decrease in TB mortality rate is likely due to Newfoundland's poor nutrition and lack of centralized healthcare rather than a biological interaction between P&I and TB.

Pandemics, past and present: The role of biological anthropology in interdisciplinary pandemic studies

“…Instead, the persistent high TB mortality rates throughout the early 20th century were likely due to social factors like poor nutrition and lack of health care rather than biological interactions between the diseases. van Doren and Sattenspiel (2021) emphasized, however, that their results should not fundamentally reframe the original observations made by Noymer and Garenne. Instead, populations may exhibit different patterns of post‐pandemic changes due to their cultural, demographic, and epidemiological differences.…”

“…For example, Sawchuk (2009) showed that health quickly rebounded in Gibraltar following the pandemic, with sex differentials returning to levels comparable to prepandemic estimates. van Doren and Sattenspiel (2021) analyzed yearly age‐standardized TB mortality rates for the island of Newfoundland from 1900 to 1939, with the expectation that, to support the hypothesis, years soon after the pandemic should show significant declines in TB mortality rates. Female mortality did decline in 1928, which was too late to be confidently associated with the 1918 influenza pandemic, while there were no significant declines for males nor for both sexes combined.…”

“…Discussion of chronic diseases has largely been in a broad sense, such as the recognition that comorbid conditions helped form the backdrop of disease in different locations, contributing to the development of syndemics (Herring & Sattenspiel, 2007; Sattenspiel & Mamelund, 2012). However, as discussed above, much research has specifically investigated TB in relation to hypotheses about post‐pandemic mortality trends (Noymer & Garenne, 2000; Sawchuk, 2009; van Doren & Sattenspiel, 2021), but it is so far unclear whether this interaction was active (i.e., a biological interaction of the pathogens and/or disease processes) rather than passive (i.e., increased TB mortality during the pandemic followed by decreased mortality in subsequent decades was more attributable to an overlap in age groups at risk of death from both diseases) (Noymer, 2009). Dahal et al (2018) calculated excess mortality for TB during the pandemic using data from Arizona, which had a very high prevalence of TB at the time due to the treatment‐related benefits of its climate.…”

Contextualizing pandemics: Respiratory survivorship before, during, and after the 1918 influenza pandemic in Newfoundland

“…Results of the standardized age‐based pooled respiratory mortality calculations reveal that composite mortality is roughly W‐shaped for all time periods (Figure 2). As seen in Table 1, most of the deaths that contributed to these mortality calculations were from TB; van Doren and Sattenspiel (2021) showed that the W‐shaped pattern was prominent in TB deaths throughout the early 20th century in Newfoundland, so this observation is not unfounded. Pooled respiratory mortality during the pandemic was higher than pre‐ and post‐pandemic mortality and exhibited a more pronounced peak in ages 20–44, likely due to the contribution of pandemic influenza deaths in this category, as seen in Figure 2 and Table 2.…”

“…The population also suffered from persistent malnutrition and TB, which even in the early 20th century was known to be a severe and inseparable combination of perpetuating comorbid health conditions (Adamson et al, 1945; Aykroyd et al, 1949). van Doren and Sattenspiel (2021) highlighted these nutritional deficiencies such as skin lesions, gum swelling, and vitamin C and D deficiencies (Adamson et al, 1945) as central to high TB mortality from 1900–1939, despite the devastating impacts of strong selective effects after the 1918 flu observed elsewhere (Noymer, 2009, 2011). The comorbidity of TB and influenza is well‐observed and severe (Walaza et al, 2015, 2020), resulting in observations of selective mortality against those with both diseases and subsequent decline of TB mortality in the decades following the 1918 flu (Noymer, 2009, 2011).…”