Table 1 Variables description and operationalization, HISlink 2018, Belgium

Dependent variables – Health related outcomes

Preventive dental care among adult population aged 18 years and over

The selected indicator is the proportion of the adult population aged 18 years and over who had at least one contact with a dentist in the reference period, i.e. in 2018, for preventive care such as an oral examination, a prophylactic cleaning, scaling, etc. The specific NIHDI nomenclature codes for the preventive dental care can be found in [32].

BCHI, 2018

Purchase of antibiotic among population aged 18 years and over

This indicator is defined as the proportion of the population aged 18 years and over with at least one purchase of antibiotics between 01/07/2018 and 30/06/2019. Pharmanet data were used to identify cases of purchase of antibiotics. Purchase of a prescribed antibiotic was defined as having obtained at least one reimbursement of prescribed medicine belonging to ATC-code group J01 (antibacterials for systemic use) purchased from a public pharmacy (see Table A1 in the supplementary file). As antibiotic purchase has probably a seasonal pattern, there may be more than one peak in antibiotics use in a calendar year. Therefore in order to include only one winter peak per 12-month period, instead of the months January to December, we used the period from July 01, 2018 to June 30, 2019 to express the annual antibiotic purchase [33].

BCHI, 2018–2019

Vaccination against flu among community dwelling older people aged 65 years and older

The indicator expresses the proportion of the population aged 65 years and over that is vaccinated against flu in the reference period, i.e., calendar year 2018. Older people aged 65 years and over residing in an institution (rest homes and the rest and care homes) were excluded because in the BCHI data only vaccines which have been reimbursed are taken into account and since 2010 vaccines are free of charge for older people residing in an institution in Flanders [34]. Hence the calculations for this indicator may result in an underestimation of the true coverage rate. All vaccines belonging to the ATC 4 class J07BB (anti-influenza vaccines) were considered.

BCHI, 2018

Mental health

The purchase of antidepressants is used as a proxy of mental health. The indicator expresses the percentage of adults aged 18 years and over with at least one purchase of an antidepressant [34] (ATC code = N06A) in 2018.

BCHI, 2018

Breast cancer screening among women aged 50–69 year in 2018

Proportion of women aged 50–69 having received at least one mammogram within the last two years, i.e., within the reference year or the reference year-1. In the BCHI data source, the mammographies realized within the screening programme follow a specific procedure, and have their own billing codes. However, these codes do not allow to sufficiently discriminate screening within the program from the other mammographies (opportunistic screening, diagnostic evaluation). Therefore, in this study, all mammograms are considered, within or outside the context of the organised screening programme and we assumed that the largest part of the mammographies undergone between 50 and 69 is made for screening purposes, and therefore we used this information as a proxy of the breast cancer screening. The NIHDI nomenclature codes used can be found in Table A1 in the supplementary file.

BCHI, 2017–2018

Perceived health status among population aged 18 years and over

Perceived health status is based on the single question: “How is your health in general?”. This question is part of the Minimum European Health Module (MEHM), which is internationally used. Five response categories are possible: Very good / Good / Fair / Poor / Very poor. The response categories Very good / Good are recorded as “Good” and those Fair / Poor / Very poor as “Poor”.

BHIS, 2018

Physical activity among population aged 18 years and over

This refers to non-work-related physical activity (leisure-time physical activity and/or the use of a bicycle for commuting) meeting WHO recommendations: spend at least 150 min per week in physical activities of at least moderate intensity. The Physical Activity Questionnaire developed by European Health Interview Survey (EHIS-PAQ) was used to assess physical activity. This is a dichotomous variable (Practice of physical activity / No practice of physical activity).

BHIS, 2018

Type of diet among population aged 18 years and over

The type of diet was assessed using a short food frequency questionnaire. The indicator refers to the proportion of the population aged 18 years and over who eat the recommended daily amount of fruit and vegetables, i.e., at least 5 portions fruits and vegetables (Healthy diet) or not (Unhealthy diet).

BHIS, 2018

Consumption of alcohol among population aged 18 years and over

The EHIS wave 3 questions [35] are used to measure alcohol consumption in order to comply to the European Regulation which recommends the use of a harmonized approach in all EU Member States. The indicator expresses the drinking frequency in the past 12 months preceding the survey: Daily / Weekly / Monthly / Less than monthly / None. These categories are dichotomized as: at least once a week/less than once a week) among the population aged 18 years.

BHIS, 2018

Consumption of tobacco among population aged 18 years and over

Proportion of the population aged 18 and over who currently smoke (daily or occasionally). The tobacco consumption is a dichotomous variable (Yes / No).

BHIS, 2018

Independent variables

Educational attainment

Educational attainment is based on the highest level of education achieved in the household. Possible values are “primary or no degree”, “secondary inferior”, “secondary superior”, and “superior education” following the ISCED-11 classification, whereby superior education includes all obtained degrees higher than secondary superior [36]. These values are recorded into two categories for the analyses: higher secondary education or lower (“primary or no degree”, “secondary inferior”, “secondary superior”) and higher education (“superior education”).

BHIS, 2018

Household income level

The quintiles of the equivalent household income (quintile 1: <750, quintile 2: 751–1000, quintile 3: 1001–1500, quintile 4: 1501–2500, quintile 5: >2500) were recoded in low (quintile 1–3) and high (quintile 4 and 5).

BHIS, 2018

Mediator variable

Health literacy (HL) among population aged 18 years and over

The HL level was assessed in the BHIS 2018, using the 6-items European Health Literacy Survey Questionnaire (HLS-EU-Q6), which is a short- form of the original 47-items tool (HLS-EU-Q47) [31]. Like the original, the HLS-EU-Q6 is a self-reported tool whereby participants are asked how easy or difficult they find it to perform an information-related task, using Likert-type responses (“very easy” = 4; “fairly easy” = 3; “fairly difficult” = 2; “very difficult” = 1. “Don’t know” or refusal were recoded as missing. The six items covered are:

• Judge when you may need to get a second opinion from another doctor

• Use information the doctor gives you to make decisions about an illness

• Find information on how to manage certain mental health problems like stress or depression

• Judge if the information on health risks in the media is reliable? (Examples: TV, Internet or other media)

• Find out about activities that are good for your mental well-being? (Examples: meditation, sport, walking,…)

• Understand information in the media on how to get healthier? (Examples: Internet, newspapers, magazines).

The scale final score measuring HL is the mean value on the six items, which varies between 1 and 4. Only respondents who answered at least 5 items were considered. Based on the final score, three possible levels of HL are defined: insufficient level of HL (1 ≤ x ≤ 2); limited level of HL (2 < x < 3); sufficient level of HL (3 ≤ x ≤ 4). In this study, HL was a dichotomous variable grouping together insufficient and limited levels of HL as “low HL” - vs. ”sufficient level of HL”.

BHIS, 2018

Confounding variables

Age

Respondents age (in years)

BHIS, 2018

Sex

Respondents gender (Male / Female)

BHIS, 2018