Associations of mortality with own height using son's height as an instrumental variable

David Carslake,Abigail Fraser,George Davey Smith,Margaret May,Tom Palmer,Jonathan Sterne,Karri Silventoinen,Per Tynelius,Debbie A Lawlor,Finn Rasmussen

doi:10.1016/j.ehb.2012.04.003

Abstract

Height is associated with mortality from many diseases, but it remains unclear whether the association is causal or due to confounding by social factors, genetic pleiotropy,11Pleiotropy is the influence of one gene on multiple phenotypic traits. or existing ill-health. The authors investigated whether the association of height with mortality is causal by using a son's height as an instrumental variable (IV) for parents’ height among the parents of a cohort of 1,036,963 Swedish men born between 1951 and 1980 who had their height measured at military conscription, aged around 18, between 1969 and 2001. In a two-sample IV analysis adjusting for son's age at examination and secular trends in height, as well as parental age, and socioeconomic position, the hazard ratio (HR) for all-cause paternal mortality per standard deviation (SD, 6.49cm) of height was 0.96 (95% confidence interval (CI): 0.95, 0.96). The results of IV analyses of mortality from all causes, cardiovascular disease (CVD), respiratory disease, cancer, external causes and suicide were comparable to those obtained using son's height as a simple proxy for own height and to conventional analyses of own height in the present data and elsewhere, suggesting that such conventional analyses are not substantially confounded by existing ill-health.

Highlights

Inverse associations of height with allcause mortality have been found in a large number of studies in developed countries (Davey Smith et al, 2000; Engeland et al, 2003; Jousilahti et al, 2000; Koch, 2011; Song et al, 2003; Song and Sung, 2008)
We found that height at age 18 was inversely associated with mortality from all-causes, cardiovascular disease (CVD), coronary heart disease (CHD), stroke, diabetes, respiratory disease, external causes and suicide
It was positively associated with mortality from cancer and, in fathers, from aortic aneurysm

Summary

Introduction

Inverse associations of height with allcause mortality have been found in a large number of studies in developed countries (Davey Smith et al, 2000; Engeland et al, 2003; Jousilahti et al, 2000; Koch, 2011; Song et al, 2003; Song and Sung, 2008) This appears to be driven by inverse associations of height with cardiovascular disease (CVD) and respiratory disease mortality (Cook et al, 1994; Gunnell et al, 2003; Lawlor et al, 2004; Lee et al, 2009; Paajanen et al, 2010), and partly counteracted by positive associations with many forms of non-smoking related cancers It is important to establish whether an association is causal before exploring the plausibility of different biological mechanisms which could provide insights into the prevention of disease

Results

Discussion

Conclusion