Cindy Boer

210 | Chapter 5.1 Flemish Gut Flora Project (FGFP) procedures were approved by the medical ethics committee of the University of Brussels/Brussels University Hospital (approval 143201215505, 5/12/2012) and all methods were performed in accordance with the Declaration of Helsinki. A declaration concerning the FGFP privacy policy was submit- ted to the Belgian Commission for the Protection of Privacy. Participants were recruit- ed through repeated announcements in print, audiovisual, and social media as well as through the FGFP website, where volunteers could enroll from January 2013 onwards The Copenhagen Prospective Study on Asthma in Childhood (COPSAC) was ap- proved by all relevant authorities including the Danish Ethical Committee (H-B-2008- 093), and the Danish Data Protection Agency (2015-41-3696) and all methods were performed in accordance with the Declaration of Helsinki. Both parents provided in- formed consent prior to participation. Comparing the gut microbiome profiles and functions between children and adults To compare gut microbiome profiles between children and adults, we selected sam- ples from European participants. Ethnic background of GenR participants was assessed based on self-reported country of birth of four grandparents as described elsewhere[43]. Ethnic background of RS participants was assessed based on self-reported ethnic back- grounds of the four grandparents. We selected European participants by combining all European countries together with Americans, Oceanics and North Africans as evaluated elsewhere[44]. In short, the participant was deemed to be of non-Dutch origin if one parent was born abroad. If both parents were born abroad, the country of birth of the participant’s mother defined the ethnic background. Ethnicities of the parents were de- rived from the grandparents using the same protocol. The different ethnicities based on the parents country of birth or ethnic background were narrowed to three main ances- try groups: Europeans, including all European countries, together with Americans, Oce- anics, and North Africans (with parents from Algeria, Egypt, Libya, Morocco, Sudan, Tu- nisia, and Western Sahara); Africans, including Sub‐Saharan Africans, Dutch Antilleans, and Surinamese Creoles; and Asians, including all Asian countries and Surinamese Hin- dustanis. Reads were subsampled at 10,000 reads per sample and pooled. Classification was performed (as described above) in one combined run. Shannon α-diversities were calculated and tested for significant differences between the two cohorts using Wilcox- on signed-rank test (1000 permutations). Between-sample Bray-Curtis dissimilarities were calculated and principal coordinate analysis (PCoA) was performed and tested for significant differences between the two cohorts using PERMANOVA. During the beta diversity analysis we adjusted for DNA isolation batch and time in mail since these were