comparatively shown for Denmark and The Netherlands, 1913–1922, with the time indicated for an abrupt change in nutrition for the Danish population as a result of policy change imposed by the warring countries, data from [28].
Malnutrition
It is well established that malnutrition adversely affects the functioning of the immune system, both innate and acquired, in its defense mechanisms against a broad range of infectious diseases [20]. Whether malnutrition actually increases the risk of TB among individuals infected with M. tuberculosis has been subject to substantial discourse. The most authoritative review to-date is that by Cegielski and McMurray [21] who conclude that malnutrition is an important risk factor for TB. Under this premise, the role of malnutrition on TB incidence in wartime is discussed in the following.
Malnutrition with hypovitaminoses and hypoproteinemia remain prevalent in some low-income countries [22] and are postulated to be a major cause of the rise in TB during wartime. Deficiencies usually result from the disruption of agricultural production or food supply lines, imposition of food rationing and distribution controls. Extreme examples are Nazi-governed concentration camps and the famine, near-starvation 900-day-long siege of Leningrad [23].
Apart from these extremes, malnutrition is most often mentioned in the war literature as one of the main reasons for the deteriorating TB situation, but how such assertions are arrived is questionable [24]. A major review on malnutrition as a risk factor for latent infection progressing to active TB has noted how thin the evidence actually is and how much anecdotal sources cloud the subject [21]. Nevertheless, as mentioned above, the authors do conclude that malnutrition might indeed account for a substantial population attributable risk. There have been attempts to determine a relationship between TB mortality and dietary constituents; for instance in England and Wales during WWII [25] or in Denmark during the WWI [26], but remain subject to vivid discussions about fact and fiction [27]. Faber has provided a comprehensive review about nutrition during WWI and TB mortality [28]. A summary of one of his major findings is shown in Figure 4.
In 1917, mortality in the Netherlands and in Denmark was about the same. But by 1918, mortality had continued rising to a peak in the Netherlands, while it had substantially declined in Denmark. Faber recalls that Denmark’s principal occupation then was producing animal foodstuffs, such as beef, pork, butter, milk, and eggs, while it imported feed for the animals and cereals for human and animal consumption. Both Great Britain and Germany consumed a heavy share of these products, as reflected in the country’s exports and imports from 1913 to 1917. In February 1917, this changed drastically when Germany declared unrestricted marine welfare and imposed a complete blockade for food exports by Denmark. This had a significant impact on food availability: bread for instance had to be rationed, while butter was now available in abundance: while before it had been the other way around. As a result of the changes and diligent rationing, the earlier food crisis ceased in 1918. Most notably, fish and meat consumption rose to unprecedented levels, and margarine was replaced by butter, etc. The association between the change in nutrition and the reversal of the TB mortality is striking to say the least. Causality cannot necessarily be inferred from this association. The enthusiasm of Faber for animal proteins and fat could not of course remain undisputed [29]. Malmros used the example of Norway to show that a moderately reduced calorie supply – as was the case throughout the war – does not lead necessarily to substantially increased TB morbidity (see also Fig. 9, [30]), provided the conditions are otherwise favorable.
Fig. 5. Time from year of death elapsed since average time of diagnosis, back-calculated for Chemnitz, Germany, unpublished data from Fröhlich, reported by Klesse [15].
Tuberculosis fatality increased in Berlin stepwise during WWII from 19.0 in 1939 to 49.5% in 1945 when almost half of all TB patients died from the disease, most probably, as Meyer assumes, due to the lowered resistance to the disease caused by undernourishment, in particular protein deficiency [14].
The observation that TB became a more acute disease during wartime is underlined by data from the Moselle region in Germany, in which the survival time from diagnosis to death became much shorter during the war period 1940–1945 than in comparable periods before and after [31]. This was also observed by Fröhlich in Chemnitz/Saxony [15], as shown in Figure 5.
In 1946, Leyton reported that Russian POWs had more severe TB than British POWs and that there were large differences in the frequency of TB between British and Russian POWs. He also assumed that malnutrition stood out as the only causative factor among the Russians [24].
Brozek et al. [23] observed a more acute and severe course of TB in their report on the health consequences of semi-starvation in the Leningrad siege, one of the longest and most destructive sieges in history and possibly the costliest in terms of casualties: “The increase in the incidence of TB was gradual, a few cases appearing December 1941, the peak being in May and June 1942. Much TB was seen, but remarkable was the fulminating character of the TB with hemorrhagic pleural effusion, widespread pulmonary disease and damage, miliary spread, and early death.”
Daniels describes for France that in regions with ample supply of animal food and milk (Normandy, Brittany, Eastern France), where there had always been a high TB mortality, the rate declined throughout the war in contrast to regions with severe food shortages which showed a substantial rise, most prominently in Paris from 155 in 1938 to 215 per 100,000 population in 1941 [3].
Other Host-Dependent Factors
Stress
Severe physical and mental stress (which may also weaken the immunologic resistance to TB [5]) was incurred during wartime in both civilian workers and those occupied in ammunition production or in military service. Innes, for example, explains the higher percentage of female deaths compared with pre-war years in the county of Rochdale (near Manchester/England), with the more extensive employment of women in the heavy industries for longer hours with less time and energy to devote to housekeeping [11].
Age and Sex
It is well-known that TB frequency may differ substantially by age and sex. During wartime,