Introduction There remains uncertainty around the impact of war on the lifespan of First World War (WW1) veterans. In particular, study comparison groups do not typically consider the ‘healthy soldier effect’.

Methods We obtained lifespan data on a random sample of 857 war-exposed New Zealand WW1 veterans and compared this with lifespans of a non-war military cohort (n=1039). This comparison was possible as the non-war-cohort arrived in Europe too late to participate in the war, allowing a ‘natural experiment’ that avoided the ‘healthy solider effect’.

Results The lifespan comparisons indicated lower mean lifespan in the war-exposed veteran cohort compared with the non-war veteran cohort (69.7 vs 71.1 years; p=0.0405). This gap persisted (range: 0.8–1.1 years) but was no longer statistically significant when only considering the non-Māori ethnic grouping (nearly all European/Pākehā personnel), when excluding additional deaths in the immediate postwar period up to 31 December 1923, and when excluding participation in any other wars. This was the case in both analysis of variance and Cox proportional hazards regression adjusting for year of birth and occupational status. Within the war-exposed cohort, there were suggestive patterns of increasing lifespan with increasing occupational status and military rank (eg, 69.5, 70.0 and 70.7 mean years as group-level occupational status progressively increased). There were also stark differences in lifespan of 8.3 years between Māori (Indigenous) and non-Māori veterans (p=0.0083).

Conclusions The pattern of reduced lifespan in war-exposed versus non-war-exposed veterans was compatible with a smaller previous New Zealand study with comparable methodology. Veterans who were Māori had significantly lower lifespans than non-Māori veterans. There are a number of feasible avenues to further improve this type of work with existing data sources.