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Early-life disease exposure and associations with adult survival, cause of death, and reproductive success in preindustrial humans

Citation
Hayward A, Rigby F & Lummaa V (2016) Early-life disease exposure and associations with adult survival, cause of death, and reproductive success in preindustrial humans, Proceedings of the National Academy of Sciences, 113 (2), pp. 8951-8956.

Abstract
A leading hypothesis proposes that increased human life span since 1850 has resulted from decreased exposure to childhood infections, which has reduced chronic inflammation and later-life mortality rates, particularly from cardiovascular disease, stroke, and cancer. Early-life cohort mortality rate often predicts later-life survival in humans, but such associations could arise from factors other than disease exposure. Additionally, the impact of early-life disease exposure on reproduction remains unknown, and thus previous work ignores a major component of fitness through which selection acts upon life-history strategy. We collected data from seven 18th- and 19th-century Finnish populations experiencing naturally varying mortality and fertility levels. We quantified early-life disease exposure as the detrended child mortality rate from infectious diseases during an individual’s first 5 y, controlling for important social factors. We found no support for an association between early-life disease exposure and all-cause mortality risk after age 15 or 50. We also found no link between early-life disease exposure and probability of death specifically from cardiovascular disease, stroke, or cancer. Independent of survival, there was no evidence to support associations between early-life disease exposure and any of several aspects of reproductive performance, including lifetime reproductive success and age at first birth, in either males or females. Our results do not support the prevailing assertion that exposure to infectious diseases in early life has long-lasting associations with later-life all-cause mortality risk or mortality putatively linked to chronic inflammation. Variation in adulthood conditions could therefore be the most likely source of recent increases in adult life span.

Keywords
inflammation; stress; infection; life history; fitness

StatusPublished
AuthorsHayward Adam, Rigby Francesca, Lummaa Virpi
Publication date08/2016
Publication date online25/06/2016
Date accepted by journal17/06/2016
PublisherNational Academy of Sciences of the United States of America
ISSN 0027-8424
LanguageEnglish

Journal
Proceedings of the National Academy of Sciences: Volume 113, Issue 2

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