Indrikis Krams1,2,3, Severi Luoto4,5, Anna Rubika6, Tatjana Krama1,3, Didzis Elferts7, Ronalds Krams3, Sanita Kecko3, Ilona Skrinda8, Fhionna R Moore9, Markus J Rantala10,11. 1. Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia. 2. Department of Zoology and Animal Ecology, Faculty of Biology, University of Latvia, Rīga, Latvia. 3. Department of Biotechnology, Daugavpils University, Daugavpils, Latvia. 4. English, Drama and Writing Studies, University of Auckland, Auckland, New Zealand. 5. School of Psychology, University of Auckland, Auckland, New Zealand. 6. Department of Anatomy and Physiology, Daugavpils University, Daugavpils, Latvia. 7. Department of Botany and Ecology, Faculty of Biology, University of Latvia, Rīga, Latvia. 8. Daugavpils Regional Hospital, Daugavpils, Latvia. 9. School of Psychology, University of Dundee, Dundee, United Kingdom. 10. Department of Biology, University of Turku, Turku, Finland. 11. Turku Brain and Mind Centre, University of Turku, Turku, Finland.
Abstract
OBJECTIVES: Male height and health affect a diverse range of social and economic outcomes such as competition for resources and mates. Life history theory predicts that limited availability of bioenergetic resources curbs the development of central life history functions such as somatic growth, immunity, and investment in offspring. Although genetic factors are important determinants of height, other factors such as income level may affect the incidence of infections during ontogeny, thus having indirect effects on somatic growth. We tested whether growing up in families with a higher income positively affects height and immune function. MATERIALS AND METHODS: Seventy-three young Latvian men from various socioeconomic backgrounds were given a hepatitis B vaccine. Blood samples were subsequently collected to measure the antibodies produced in response to the vaccination. Tweedie compound Poisson generalized linear models were used to examine relationships between height, family income, and antibody titers. RESULTS: Both height and family income positively correlated with the strength of men's immune response. However, when testing for the simultaneous effects of height and income on antibody titers, the statistical models showed that height affected antibody levels indirectly because income level mediated variance in height. DISCUSSION: The results of this study show that the relationships between height and immune function in young men are more complex than previously thought. Associations between taller stature of men and the robustness of their immune response are indirect because resource availability affects both somatic growth and the development of the immune system.
OBJECTIVES: Male height and health affect a diverse range of social and economic outcomes such as competition for resources and mates. Life history theory predicts that limited availability of bioenergetic resources curbs the development of central life history functions such as somatic growth, immunity, and investment in offspring. Although genetic factors are important determinants of height, other factors such as income level may affect the incidence of infections during ontogeny, thus having indirect effects on somatic growth. We tested whether growing up in families with a higher income positively affects height and immune function. MATERIALS AND METHODS: Seventy-three young Latvian men from various socioeconomic backgrounds were given a hepatitis B vaccine. Blood samples were subsequently collected to measure the antibodies produced in response to the vaccination. Tweedie compound Poisson generalized linear models were used to examine relationships between height, family income, and antibody titers. RESULTS: Both height and family income positively correlated with the strength of men's immune response. However, when testing for the simultaneous effects of height and income on antibody titers, the statistical models showed that height affected antibody levels indirectly because income level mediated variance in height. DISCUSSION: The results of this study show that the relationships between height and immune function in young men are more complex than previously thought. Associations between taller stature of men and the robustness of their immune response are indirect because resource availability affects both somatic growth and the development of the immune system.