title: The impact of physical connectedness on body height in Swiss conscripts.
abstract: BACKGROUND
  Human populations differ in height. Recent evidence suggests that social networks play an important role in the regulation of adolescent growth and adult height. We further investigated the effect of physical connectedness on height.
  
  
  METHODS
  We considered Switzerland as a geographic network with 169 nodes (district capitals) and 335 edges (connecting roads) and studied effects of connectedness on height in Swiss conscript from 1884 - 1891, 1908 - 1910, and 2004 - 2009. We also created exponential-family random graph models to separate possible unspecific effects of geographic vicinity.
  
  
  RESULTS
  In 1884 - 1891, in 1908 - 1910, and in 2004 - 2009, 1(st), 2(nd) and 3(rd) order neighboring districts significantly correlate in height (p < 0.01). The correlations depend on the order of connectedness, they decline with increasing distance. Short stature districts tend to have short, tall stature districts tend to have tall neighbors. Random network analyses suggest direct road effects on height. Whereas in 1884 - 1891, direct road effects were only visible between 1(st) order neighbors, direct road effects extended to 2(nd) and 3(rd) in 1908 - 1910, and in 2004 - 2009, also to 4(th) order neighbors, and might reflect historic improvements in transportation. The spatial correlations did not significantly change when height was controlled for goiter (1884 - 1889) and for median per capita income (2006), suggesting direct road effects also in goiter-allowed-for height and income-allowed-for height.
  
  
  CONCLUSIONS
  Height in a district depends on height of physically connected neighboring districts. The association decreases with increasing distance in the net. The present data suggest that people can be short because their neighbors are short; or tall because their neighbors are tall (community effect on growth). Psycho-biological effects seem to control growth and development within communities that go far beyond our current understanding of growth regulation.
authors.affiliation: Aschauhof, 24 340 Altenhof, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hermanussen
authors.affiliation: University of Potsdam, Institute of Biochemistry and Biology, Potsdam-Golm, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Alt
authors.affiliation: Centre for Evolutionary Medicine, Institute of Anatomy, University of Zurich, Zurich, Switzerland.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Staub
authors.affiliation: Otto-Friedrich-Universität Bamberg, Bamberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Aßmann
authors.affiliation: University of Potsdam, Institute of Biochemistry and Biology, Potsdam-Golm, Germany.
authors.forename: Detlef
authors.initials: D
authors.lastname: Groth
mesh_terms: D000328:Adult; D000885:Anthropology, Physical; D001827:Body Height / Q000502:physiology*; D006801:Humans; D008297:Male; D008889:Military Personnel / Q000706:statistics & numerical data*; D013557:Switzerland / Q000453:epidemiology; D055815:Young Adult