Cindy Boer

206 | Chapter 5.1 findings on the differences in gut microbiota between 2,111 children aged 9-12 years and 1,427 adults >40 years of age living in the same city with similar urban surround- ings. Methods Study populations and sample collection The Generation R Study (GenR) is a population-based prospective multi-ethnic preg- nancy cohort study from foetal life until young adulthood conducted in the city of Rotterdam[24]. The study was designed to identify early environmental and genetic factors and causal pathways underlying normal and abnormal growth during devel- opment during childhood. GenR recruited 9,749 children undergoing several rounds of follow-up after birth. Stool sample collection started in 2012 at a mean age of 9.8 years (SD: 0.32). Ethics approval was obtained from the Medical Ethical Committee of Erasmus MC (MEC-2012-165) and written informed consent was obtained from all par- ticipants’ parents. All methods were performed in accordance with the Declaration of Helsinki. The Rotterdam Study (RS) is a prospective population-based cohort study estab- lished in 1990 to study determinants of disease and disability in Dutch adult individu- als. The original design and updates of this study have been described in detail[25]. RS consists of four sub-cohorts and comprises approximately 18,000 inhabitants of the Ommoord suburb in Rotterdam (which is predominantly populated by individuals of European ethnicity (about 96%)), aged ≥40 years. The collection of fecal samples start- ed in 2012 among the RS-III sub-cohort comprising 3,932 participants. This study was approved by the Medical Ethical Committee of Erasmus MC (MEC-02-1015) and by the Ministry of Health, Welfare and Sport of the Netherlands. All subjects provided written consent prior to participation in the study. All methods were performed in accordance with the Declaration of Helsinki. Stool samples were collected at home by the participants using a Commode Spec- imen Collection System (Covidien, Mansfield, MA). An aliquot of approximately 1g was transferred to a 25×76mm feces collection tube (Minigrip Nederland, Lelystad, The Netherlands) without preserving agent included and sent through regular mail to the Erasmus MC. A short questionnaire addressing date and time of defecation, current or recent antibiotics use (past year), recent probiotics use (past 3 days), and recent travel activities (past month), was filled out by the participants and included in the package.