The surveys collected the following meal-timing information during the week and on weekends: timing of breakfast, lunch and dinner (as drop down menu with 1-h intervals, e.g., from 12:00 till 13:00), snacks between meals (“yes”/”no”), snack between breakfast and lunch (“yes”/”no”), snack between lunch and dinner (“yes”/”no”), snack between dinner and breakfast (“yes”/”no”) and timing of last snack of the day (hours, minutes). We used the midpoint of the intervals of the hourly bins (e.g., “12:00–13:00″ was substituted by 12:30) to create pseudocontinuous variables for the time of breakfast, lunch and dinner. The continuous variable nighttime fasting was defined as the time elapsed between the last and the first meal of the day. We created two additional continuous variables: last meal to bed time (hours) and eating midpoint (hours), defined as the midpoint between the first and the last meal of the day. We also generated the discrete variable number of eating occasions (ranging from 0 to 6, the maximum number of eating occasions that could be reported in the surveys), which included main meals and snacks, and a dichotomous variable, breakfast skipping (“skipping” vs. “eating”). Each variable was calculated independently for weekdays and weekends.
The survey collected detailed information on sleep duration, sleep timing and sleep quality. We used the 3rd edition of the International Classification of Sleep Disorders (ICSD-III) [27 ] to define chronic insomnia (“yes”/”no”), as explained in Weitzer et al. [28 (link)]. The surveys also collected information on self-rated health status (“In your opinion: How is your health status in general?”, one answer possible: “very good”/“good”/“moderate”/“bad”/“very bad”) and diagnosed medical conditions (“During the past 12 months, did you have any of the following diseases or conditions?”; multiple answers possible). With this information, we defined the following dichotomous (“yes”/“no”) outcome variables: depression, diabetes, hypertension and bad or very vad self-rated health status. Participants also reported their height and weight, which were used to calculate BMI and define obesity [“yes” (BMI ≥ 30 kg/m2)/ “no” (BMI < 30 kg/m2)].
The survey also collected information on sex and age (“How old are you?”, with respondents asked to fill in their age in the 2017 survey, and to choose one of the following categories in the 2020 survey: “ < 20” / “20–24” / “25–29” / “30–34” / “35–39” / “40–44” / “45–49” / “50–54” / “55–59” / “60–64” / “65–69” / “ ≥ 70”) and other confounders and effect modifiers of interest, i.e. self-rated chronotype (“One hears about “morning” and “evening” types of people. Which ONE of these types do you consider yourself to be?”, one answer possible: “definitely a morning type”/ “rather more a morning than an evening type”/ “rather more an evening than a morning type”/ “definitely an evening type”), marital status (“What is your current marital status?”, one answer possible: “single”/ “married or in a partnership”/ “divorced”/ “widowed”), work status [“What is your current work status?”, multiple answers possible: “(self-) employed full-time” / “(self-) employed part-time” / “retired” / “unemployed” / “student, further training, unpaid work experience” / “disabled” / “in compulsory military or community service” / “household”], alcohol consumption [“How much alcohol do you drink per week? (Please give approximate/average amounts)”, with respondents asked to fill in the number of glasses of beer and wine and shots of liquor/whiskey/gin etc. consumed per week], smoking status (“Do you currently smoke?”, one answer possible: “No, never”/“No, not anymore”/“Yes, I currently smoke”) and history of nightshifts (“Have you ever worked night shifts (schedule including ≥ 3 h of work between 12 pm and 6 am and at least 3 nights/month)?”, one answer possible: “No” / “Yes, in the past” / “Yes, currently”).
The survey collected detailed information on sleep duration, sleep timing and sleep quality. We used the 3rd edition of the International Classification of Sleep Disorders (ICSD-III) [27 ] to define chronic insomnia (“yes”/”no”), as explained in Weitzer et al. [28 (link)]. The surveys also collected information on self-rated health status (“In your opinion: How is your health status in general?”, one answer possible: “very good”/“good”/“moderate”/“bad”/“very bad”) and diagnosed medical conditions (“During the past 12 months, did you have any of the following diseases or conditions?”; multiple answers possible). With this information, we defined the following dichotomous (“yes”/“no”) outcome variables: depression, diabetes, hypertension and bad or very vad self-rated health status. Participants also reported their height and weight, which were used to calculate BMI and define obesity [“yes” (BMI ≥ 30 kg/m2)/ “no” (BMI < 30 kg/m2)].
The survey also collected information on sex and age (“How old are you?”, with respondents asked to fill in their age in the 2017 survey, and to choose one of the following categories in the 2020 survey: “ < 20” / “20–24” / “25–29” / “30–34” / “35–39” / “40–44” / “45–49” / “50–54” / “55–59” / “60–64” / “65–69” / “ ≥ 70”) and other confounders and effect modifiers of interest, i.e. self-rated chronotype (“One hears about “morning” and “evening” types of people. Which ONE of these types do you consider yourself to be?”, one answer possible: “definitely a morning type”/ “rather more a morning than an evening type”/ “rather more an evening than a morning type”/ “definitely an evening type”), marital status (“What is your current marital status?”, one answer possible: “single”/ “married or in a partnership”/ “divorced”/ “widowed”), work status [“What is your current work status?”, multiple answers possible: “(self-) employed full-time” / “(self-) employed part-time” / “retired” / “unemployed” / “student, further training, unpaid work experience” / “disabled” / “in compulsory military or community service” / “household”], alcohol consumption [“How much alcohol do you drink per week? (Please give approximate/average amounts)”, with respondents asked to fill in the number of glasses of beer and wine and shots of liquor/whiskey/gin etc. consumed per week], smoking status (“Do you currently smoke?”, one answer possible: “No, never”/“No, not anymore”/“Yes, I currently smoke”) and history of nightshifts (“Have you ever worked night shifts (schedule including ≥ 3 h of work between 12 pm and 6 am and at least 3 nights/month)?”, one answer possible: “No” / “Yes, in the past” / “Yes, currently”).
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