Data Collection Logistics

Data were collected between September 2018 and February 2020. During this period, with the help of IBGE’s digital grids¹¹, the streets of the PSU were always covered in a clockwise direction, with the supervisor’s right arm facing the houses to count the households. When selected, a multi-professional trained team visited a household.

After clarification on ethical procedures and data collection, residents of the households were invited to participate in the research and, in case of acceptance and by signing the Informed Consent Form and the Free and Informed Assent (for minors). Data collection was started immediately or scheduled according to the availability of residents.

If any selected household was unavailable on the first visit, the researchers returned to the household three times, on different days and times, including one day on the weekend or on a holiday. After the attempts, if they remained closed, these households were excluded. In the case of closed households, the team used an informative pamphlet about the research, containing clarifications, a telephone number, and an invitation to participate.

To give visibility to the Survey and with a view to clarifying the population in general about the existence of the research, the study was disseminated in various media such as radio, social networks, newspapers broadcast on open TV, and written newspapers. Furthermore, information leaflets were distributed at the research sites.

The collection in the households was carried out in two stages. The first stage took place by the application of structured questionnaires by trained interviewers with mobile devices (cellphones and tablets) and the Epicollect 5® (Imperial College London, 2018), available at https://five.epicollect.net/. The questionnaires used in the survey were based on questionnaires previously used in population-based surveys developed in the country: Inquérito de Saúde no município de São Paulo (Health Survey in the city of São Paulo), in 2015¹², and Pesquisa Nacional de Saúde (National Health Survey), in 2013¹³.

Teams collected sociodemographic, economic, access to health and sanitation services, current and past health status, violence and safety, self-reported morbidities, medication use, lifestyle, eating habits, and physical activity data. Moreover, at this stage, anthropometric data were also collected (weight, height, waist circumference, arm circumference, calf circumference, and skin folds) and blood pressure was measured. In order to reduce errors, all anthropometrists and technicians responsible for measuring blood pressure were trained and standardized according to the same methodology, and all measurements were collected in duplicate. Specifically for anthropometric measurements, training was carried out by the team from the Laboratory of Nutritional Assessment of Populations (LANPOP), from the Faculdade de Saúde Pública of the Universidade de São Paulo (Faculty of Public Health/ University of São Paulo), a partner in carrying out the ISAD-PI.

Questions related to the household, including access to health and sanitation services, family income, and goods were addressed to the head of the family, identified by the residents themselves. In the absence of the head of household or his refusal to answer the questions, another capable family member answered the questions.

Due to logistical reasons, only in the municipality of Teresina we carried out a second collection stage, following the same sampling plan, so 50% of the households drawn in each sector were systematically selected, forming a sub-sample. For this, in addition to the data collected in the first stage, adolescents (10 to 19 years old), adults (20 to 59 years old), and older adults (60 years old or more) residing in households included in the sub-sample, households were invited to participate in data collection on food consumption, by the application of 24-hour food recall (Sample-R24hs) and blood collection (Blood-sample) for subsequent biochemical analysis (glycemia and lipid profile).

Blood collection was performed at home by trained nurses, on days scheduled according to the availability of residents. Guidance for participants was provided in writing at the first home visit and reinforced by phone call the day before the collection date. They followed a standardized script, including 12-hour fasting for food and non-alcoholic beverages, 72-hour fasting for alcoholic beverages, and no physical activity or physical effort on the day scheduled for collection.

The R24hs was applied by trained nutritionists, using the multiple-pass method interview technique, which consists of an interview guided in five stages with the objective of reducing underreporting of food consumption¹⁴. Furthermore, after an interval of 2 months, face-to-face reapplication of the 24-hour recall was performed in 40% of the sample that responded to the first recall.