Participants indicated their habitual consumption of food items as absolute frequencies in times per day, per week, per month, per year, or as never, e.g. 'How often do you habitually eat raw vegetables during a meal in the winter?'.
Two items on habitual sleep duration and sleep quality were used [ 36].
In this study, to examine the prevalence of habitual clenching, we included four items in the questionnaire (Table I) [ 17,18].
Parents are asked to base their responses on their usual dietary behaviors over the previous 12 months, reporting their habitual intake of 18 food items grouped in 3 food categories.
The children's food and drink intake was reported by their parents using a retrospective food frequency questionnaire (FFQ), which asked about habitual daily consumption of 39 food items, 11 types of dinks, 13 snack items and 5 main meals during the last 6 months.
Finally, another open-format item asked about habitual actions taken when sick or dead poultry was found on the farm.
Information on habitual food consumption of 178 food items, covering the previous year, was collected using a validated, self-administered, semi-quantitative food frequency questionnaire (FFQ) developed for the Dutch cohorts of the European Prospective Investigation Into Cancer EPICC) Study [21].
Two items assessed evidence of habitual behaviour (Additional file 1, Section 1, Items 7a & b).
The eating habits of children and mothers are assessed with a FFQ that includes questions about habitual dietary intake of certain food items as well as intake of beverages, and is complemented by questions about regularity of breakfast eating.
Participants reported habitual physical activity from a 20-item questionnaire, 9 a question about usual walking pace (slow/average/brisk/fast), current smoking levels, weekly alcohol intake (units per week) and self-rated health (excellent/very good/good/fair/poor).
