title: Design, Response Rates, and Population Characteristics of a Cross-Sectional Study in Zanzibar, Tanzania.
abstract: BACKGROUND
  Data on nutritional status and correlates of noncommunicable diseases are scarce for resource-poor settings in sub-Saharan countries. With the scope of a project, "Access to Food and Nutrition Status of the Zanzibari Population," data for investigating public health questions were collected using proven measurement and laboratory standards.
  
  
  OBJECTIVE
  The present study aims at providing a descriptive overview of recruitment approaches, standardization, quality control measures, and data collection, with special attention to the design, responses, and participant characteristics of the overall project.
  
  
  METHODS
  A cross-sectional study across 80 randomly selected Shehias (wards) was conducted in 2013 in Unguja Island, Zanzibar. Examinations included all members living in 1 household, face-to-face interviews and anthropometric measurements (weight, height, mid-upper arm circumference, waist and hip circumference, and body composition) were assessed for all household members, blood pressure was taken from participants older than 2 years, and biosamples (urine and blood) from eligible household members were collected. Data collected from the core sample included sociodemographic data, nutritional status, and medical history (hypertension). Physical activity data was collected from a subsample of children between 3 and 16 years of age.
  
  
  RESULTS
  A total of 1314 participants (mean age 23.6 ± 18.9 years, 54.54% female) completed all anthropometric measurements and were included in the analysis. Out of which, 98.40% (1293/1314) completed the household member's questionnaire, 93.32% (1229/1314) participants older than 2 years completed blood pressure measurements, and 64.31% (845/1314) blood samples were collected from participants older than 5 years. Underweight prevalence for the total study population was 36.53% (480/1314) with the highest prevalence in children under 14 years. Overweight and obesity was highest among females with the prevalence of 7.61% (100/1314) and 6.62% (87/1314), respectively; obesity was rare among male participants.
  
  
  CONCLUSIONS
  The study provides valuable data to investigate the interplay of socioeconomic, demographic, environmental, physiological, and behavioral factors in the development of diet-related disorders in a representative sample of the Zanzibari population.
authors.affiliation: Leibniz Institute for Prevention Research and Epidemiology-BIPS, Bremen, Germany.
authors.forename: Maria Adam
authors.identifier: http://orcid.org/0000-0002-3073-3905
authors.initials: MA
authors.lastname: Nyangasa
authors.affiliation: Center for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany.
authors.forename: Soerge
authors.identifier: http://orcid.org/0000-0001-5277-9421
authors.initials: S
authors.lastname: Kelm
authors.affiliation: Environmental Analytical Chemistry and Eco-toxicology Lab, State University of Zanzibar, Zanzibar, United Republic of Tanzania.
authors.forename: Mohammed Ali
authors.initials: MA
authors.lastname: Sheikh
authors.affiliation: Leibniz Institute for Prevention Research and Epidemiology-BIPS, Bremen, Germany.
authors.forename: Antje
authors.identifier: http://orcid.org/0000-0001-7354-5958
authors.initials: A
authors.lastname: Hebestreit
keywords: anthropometric measures; biosamples; blood pressure; cross-sectional study; response rates; sub-Saharan Africa