National Statistical Institute

"Health and Justice Statistics" Department

Evelin Yordanova

Head of department

2, P. Volov Str.; 1038 Sofia, Bulgaria

[email protected]

+359 2 9857 459

The survey is a part of the European Health Survey System in the framework of the European Statistical System. The EHIS aims at measuring on a harmonised basis and with a high degree of comparability among EU Member States, the health status, life style (health determinants) and health care services use of the EU citizens.

EHIS wave 1

The survey was carried out by NSI based on harmonized instruments in 2008. The questionnaire for the first round of the EHIS (2007 - 2008) was adopted on 22 November 2006 by the Eurostat Working Group on Public Health Statistics.

The topics included in the questionnaire are developed in order to meet main needs as for the management of health care systems, as well as in science. Within these needs, EHIS questions are aimed at meeting the basic needs of information at EU level. They do not cover all detailed aspects of health which can better be carried out via specific surveys at national level.

The questionnaire consists of four modules.

• Health status;
• Health care;
• Health determinants (life style);
• Background module.

In addition, in order to meet the information needs of the European Commission`s DGs "Health and Consumers" (SANCO) and "Employment, Social Affairs and Inclusion (EMPL), 26 indicators which cover the three topics - Health status, Health care and Health determinants are calculated. Indicators are calculated using respondent`s answers during the interview. No documents are required, proving the correctness of answers and no measurements are done. All the indicators are calculated for the population aged 15 and over, except in case a specific age is indicated.

EHIS wave 2

In 2014 BNSI participated in the EHIS wave 2 in accordance with the Commission Regulation (EU) No 141/2013 implementing Regulation (EC) No 1338/2008 requrements. The survey was carried out by using the harmonized questionnaire proposed by Eurostat.

EHIS wave 3

In 2019 all Member States participated in the EHIS wave 3 in accordance with the Commission Regulation (EU) No. 2018/255 as the BNSI carried out the survey in the period October 2019 - January 2020.

The questionnaire consists of the same four modules  for all the EHIS waves. In order to reduce the responce burden and to satisfy the specific users’ needs the questionnaire is  changed.

EHIS includes the following topics:

Health status
This topic includes different dimensions of health status and health-related activity limitations:

• General health status (Minimum European health module): self-perceived health, chronic morbidity and activity limitation
• Disease-specific morbidity
• Accidents and injuries
• Health-related absenteeism from work
• Physical and sensory functional limitations
• Difficulties in personal care activities / activities of daily living (such as eating and washing) and help received/needed
• Household activities / Instrumental activities of daily living (such as preparing meals and shopping) and help received/needed
• Pain
• Aspect of mental health (psychological distress and mental well-being in the first wave, depressive symptoms in the second wave).

Health care

• Hospitalisation (in-patient and day care)
• Consultations with doctors and dentists
• Visits to specific health professionals (such as physiotherapists or psychologists)
• Use of home care and home help services
• Use of medicines (prescribed and non-prescribed)
• Healthcare preventive actions (such as influenza vaccination, breast examination, cervical smear test and blood tests)
• Unmet needs for health care.

Health determinants

• Height and weight
• Physical activity
• Consumption of fruits, vegetables and juice
• Smoking behaviour and exposure to tobacco smoke
• Alcohol consumption
• Social support.

Background variables on demography and socio-economic status.

EHIS - wave 1

• National Classification of Occupations and Duties-2005 (NCOD-2005) - consistent with the International Standard Classification of Occupations ISCO-88 (COM);
• Classification of Economic Activities (CEA-2008, for international use NACE.BG -2008) - consistent with the European classification NACE Rev. 2;
• Classification of Territorial Units for Statistical Purposes in Bulgaria (NUTS);
• International Standard Classification of Education, 1997 revision (ISCED 1997).

EHIS - wave 2 and 3

• National Classification of Occupations and Duties-2011 - consistent with the International Standard Classification of Occupations ISCO-08;
• Classification of Economic Activities (CEA-2008, for international use NACE.BG -2008) - consistent with the European classification NACE Rev. 2;
• Classification of Territorial Units for Statistical Purposes in Bulgaria (NUTS);
• International Standard Classification of Education, 2011 revision (ISCED 2011).

All persons aged 15 and over living within the selected non-institutionalised households are covered.

In accordance with the EHIS methodology people living in institutionalized households as residencies for students or workers, medical or social institutions, prisons are excluded from the target population.

Diseases - self-reported prevalence:

EHIS - wave 1

Percentage of persons reporting:

• to have the selected disease,
• the disease was diagnosed by a medical doctor,
• the disease occurred during the past 12 months.

The indicator is calculated for five diseases: diabetes, chronic depression, chronic bronchitis, chronic obstructive pulmonary disease, emphysema, asthma, incl. allergic and high blood pressure (hypertensive diseases).

EHIS - wave 2

Proportion of the population reporting a chronic condition in the past 12 months. Statistics on 15 diseases or chronic conditions are presented:

A. Asthma (allergic asthma included)

B. Chronic bronchitis, chronic obstructive pulmonary disease, emphysema

C. Myocardial infarction (heart attack) or chronic consequences of myocardial infarction

D. Coronary heart disease or angina pectoris

E. High blood pressure (hypertension)

F. Stroke (cerebral haemorrhage, cerebral thrombosis) or chronic consequences of stroke

G. Arthrosis (arthritis excluded)

H. Low back disorder or other chronic back defect

I. Neck disorder or other chronic neck defect

J. Diabetes

K. Allergy, such as rhinitis, hay fever, eye inflammation, dermatitis, food allergy or other allergy (allergic asthma excluded)

L. Cirrhosis of the liver

M. Urinary incontinence, problems in controlling the bladder

N. Kidney problems

O. Depression

Injury by accident - at home, school or leisure accident, road traffic accident. Percentage of persons reporting to have had an accident during the past 12 months, which resulted in injury.

Self-reported visits to general practitioner, dentist or orthodontist, medical specialist - Percentage of persons having consulted a doctor during the last 4 weeks.

Medicine use

EHIS - wave 1

Percentage of persons reporting to take medication prescribed by a physician for a specific disease during the past 2 weeks for diabetes; chronic depression; chronic bronchitis, chronic obstructive pulmonary disease, emphysema; asthma, incl. allergic and high blood pressure.

EHIS - wave 2

Self-reported use of prescribed and non-prescribed medicines: Proportion of the population who used medicines prescribed and non-prescribed by a doctor in the past 2 weeks.

Breast cancer screening - Percentage of women aged 50-69 years, who have undergone a mammography.

Cervical cancer screening - Percentage of women aged 20-69 years, reporting to have undergone a cervical cancer screening test.

Body Mass Index (BMI): Percentage of persons aged 18 and over with specific BMI. The indicator is calculated as ratio of weight (kg) and the square of height (m) - kg/m2. The following subdivision is used:

• underweight (less than 18.5 kg/m2)
• normal weight (between 18.5 and less than 24.99 kg/m2 )
• overweight (between 25.00 and less than 29.99 kg/m2)
• obese (equal or greater than 30.00 kg/m2)

Daily cigarettes smokers: Percentage of persons reporting to smoke cigarettes (manufactured and hand-rolled) daily. 

Hazardous alcohol consumption (EHIS - wave 1) - Percentage of persons who drink 6 and more alcohol drinks for one occasion, during the past 12 months, by frequency of use.

Persons aged 15 and over living in non-institutionalised households.

All persons aged 15 and over living in non-institutionalised households are covered.

In accordance with the EHIS methodology people that live in institutionalised households as residencies for students or workers, medical or social institutions, prisons are excluded from the target population.

The territory of the Republic of Bulgaria.

EHIS wave 1 - 2008

EHIS wave 2 - 2014

EHIS wave 3 - 2019

Not applicable.

EHIS wave2

Sampling frame

The Census 2011 DataBase is used. The sampling frame is updated annualy based on current demographic statistics as of 31.12. 2014 data are used.

Survey population

Sampling design

A two stage stratified cluster sample on national and regional level is used. The sample is stratified by using the administrative regions in the country and persons' place of residence (town, village). As a result of the stratification 56 strata are designed. At the first stage clusters are selected with a probability proportional to their size, separately for 28 districts and for urban and village population. At the second stage, through a systematic selection 6 households are identified. All persons aged 15 and over in selected households were interviewed.

Data source on Target population by sex and age is Current demographic statistics as of 31.12.2014.

Data source on Target population by Educational attainment level (ISCED 2011) and Current labour status (self-declared) is LFS 2014.

EHIS wave3

Sampling frame

Population Census 2011 data base updated with deaths and births (annually) was used as sampling frame. In the list the information for households and household’s members is eligible. The list is updated annually based on current demographic statistics data as of 31 December.

Survey population

Sampling design

The sample was stratified by administrative-territorial districts in the country (NUTS3 level) and the household’s location. As a result 56 strata were formed (28 of urban and 28 of rural population).

Taking into account the precision requirements laid down in the european legislation in the field, design effect and the planned response rate 11 629 persons aged 15 and over were initialy selected for the EHIS wave 3.

The clusters on the first stage are chosen with probability proportional to population size (number of households) in the SUs. Systematic sampling of the secondary units (households) selected in each primary unit is applied. Each SU contains the same size - 8 households. All individuals aged 15 and over are selected in each sampled household.

Data source on Target population is as follow:

- by sex and age and by degree of urbanisation - Current demographic statistics as of 31.12.2019;

- by Educational attainment level (ISCED 2011) and Labour status - LFS 2019;

- by Household size – SILC 2019.

According to the European legislation - every 5 years.

A face to face PAPI interview and self-administered part.

Interviewers

All interviewers are internal staff with experience in health/social surveys.

Ratio interviews / interviewers – 53 (2014); 75 (2019)

Interviewer training method and support 

The training of trainers is conducted (representatives from Departments "Statistical Surveys" at the Regional Statistical Offices). They are experienced in conducting the household’s surveys. Some of them participated in the previous EHIS waves .

The training programme included:

• Aims and tasks of the survey. Background and explanation of the rationale of the EHIS;
• General presentation as well as presentation in details of the survey modules. General concept of the questions, definitions, use of classifications, use of proxy interview, self-completion forms;
• Work in groups with different examples, which described the difficulties and specific features of the instrument cases that may occur. Discussion of the results and the interviewer’s opinions. How to respond to Frequently Asked Questions;
• Presentation and detailed discussion of the content of the template for interviewers notes, which are to be filled in by each interviewer after conducting the interview;
• Organization of the survey.

As a part of the training, the interviewers were provided with the detailed guideline manual for the fieldwork, containing all aspects necessary to execute the survey correctly, the questionnaire and the Self-completion forms as well as the Notes for the interviewers.

Quality control during the fieldwork

Method used for the prenotification or first contact of respondents - letter.

Use of incentives - no.

Theoretical minimal number of contacts with a respondent before declaring a nonparticipation (i.e. the number of attempts that an interviewer is asked to do for interviewing a respondent) - up to two visits for distant clusters and up to 4 visits in close clusters from the RSO location.

Interview duration for the EHIS questions:

EHIS wave 2

• Average: 30 minutes 
• Minimum: 5 minutes 
• Maximum: 65 minutes        

EHIS wave 3

• Average: 32 minutes 
• Minimum: 10 minutes 
• Maximum: 75 minutes 

Techniques used to control interviewer performance – There is a supervisor in each Department “Statistical Surveys” at RSO. A review of questionnaires and Interviewers’ notes was carried out by the supervisors in order to check whether the questionnaires were correctly filled in. Individual contacts were regularly established. Weekly reports on survey participations was provided in NSI by supervisors.

Ratio interviewers / field supervisors - 4.

Were (some of) the respondents contacted for quality control? - No.

Were additional studies performed in relation to the nonparticipation? - No.

Additional IT application for fieldwork monitoring was elaborated as well. The application allows referring for the visited, contacted and non-contacted households and persons in real time. Information on non-surveyed households and individuals as well as for the reasons for that was collected. The available information makes it possible to monitor the response rate and field work in general at the regional and national level.

Questionnaire

Development of the questionnaire

The survey was carried out in Bulgarian lenguage. The translation protocol proposed by Eurostat is used.

Were the modules pre-tested? EHIS wave 1 questionnaire was tested, EHIS wave 2 and 3 - no. 

Design of the questionnaire

The recommended order of modules and sub-modules is followed.

Modified EHIS questions in comparison with the model questionnaire and conceptual guidelines - AC2, PL6, HO1, AM7, PA1, AL1, AL6. All questions are modified in accordance with the Eurostat Methodological manual - "European Health Interview Survey (EHIS wave 2)" requirements.   

The content of alcohol in the “national standard” drink (in grams) used in AL sub-module = 14 g.

EHIS wave 1

The data are validated by Eurostat. Common rules for checking and consistency checks are applied.

EHIS wave 2

The proposed by Eurostat harmonized instrumentarium according to the "EHIS wave 2 Methodological manual" is used. Conceptual guidelines and translation protocol is also applied. Common rules for checking and consistency checks in accordance with the requirements of the Commission Regulation (EU) No 141/2013 implementing Regulation (EC) No 1338/2008 are applied. Proposed by Eurostat EDIT validation tool is used before sending the microdata file. 

EHIS wave 3

The proposed by Eurostat harmonized instrumentarium according to the „European Health Interview Survey Manual“ is used. Conceptual guidelines and translation protocol is also applied. Common rules for checking and consistency checks in accordance with the requirements of the Commission Regulation (EU) No 255/2018 implementing Regulation (EC) No 1338/2008 are applied. Proposed by Eurostat validation tool is used before sending the microdata file. 

Data checking, cleaning and editing is done in accordance with the EHIS Methodological manual, EHIS Validation rules as well as EHIS Data delivery guidelines. 

Imputation, adjustment for non-response and calibration is not applied (EHIS wave 2).

EHIS wave 3 – calibration is used.

The current demographic data for the total population is used for weighting.

EHIS wave 2

The current demographic data as of 31 December 2014 for the total population is used for weighting.

Information on the variability of final weights

average divided by minimum = 2.71
maximum divided by average = 2.55
coefficient of variation = 0.32

EHIS wave 3

The procedure for weighting was applied in three steps as follows:

• Calculation of sample’s weights, which represent the inverse of inclusion probabilities of the sample units. All sampling units receive these sampling weights;
• Non-response adjustment - the sample weights were adjusted with the survey’s results by the coefficient of responsibility;
• Calibration - data on population as of 31.12.2019 from Information System ‘Demography’ was used. Following categories were used for calibration.

Following categories were used for calibration:

• Population by administrative-territorial districts in the country (NUTS3 level) and the household’s location (56 groups - 28 of urban and 28 of rural areas);
• Population by the household’s location and sex (112 groups – 56 groups of men by urban and rural areas and 56 groups of women by urban and rural areas);
• Population by age groups and sex – men and women divided into 13 age groups: 15-19, 20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64, 65-69, 70-74, 75+ (26 groups).

There is a quality management system in the BNSI in accordance with the requirements of ISO 9001:2015. Since 2019, an extended scope of the system has been approved, including receiving, data collection, processing, storing, analyzing, providing and dissemination of statistical information.

According to the Regulation 1338/2008 on Community statistics on public health and health and safety at work EHIS is to be conducted every five years. EHIS wave 2 and 3 were conducted according to the European legislation.

EHIS aims at achieving an input standardisation. A model questionnaire (questions, answer categories, filters, etc.) as well as conceptual guidelines and rationales were prepared. Conceptual translation into all EU languages was requested. By using the Methodological manual 'European Health Interview Survey ' the harmonizad questionnaire a standard translation protocol as well as Conceptual translation cards and guidelines were applied.

National data entry tool is elaborated according to the Validation rules and Data delivery guidelines proposed by Eurostat. Data validation tool is used in order to prevalidated the national microdata before sending them to Eurostat.

The quality management system certified in accordance with ISO 9001:2015,  application of the uniform methodological documents, rules and procedures at all stages of the study ensure high quality of the data.

The produced information answers to needs as for the management of health care systems, as well as in science. In framework of these needs, EHIS questions are aimed at meeting the basic needs of information at EU level, as they do not cover all detailed aspects of health, which can better be carried out via specific surveys at national level.

Not applicable.

Persons aged 15 and over living in private households are covered. Persons up to 14 years of age as well as those living in institutionalized households, as residencies for students or workers, medical or social institutions, prisons are generally excluded from the target population.

Not applicable.

EHIS wave 2

The minimum effective sample size as is set out in Annex II of the Commission Regulation (EU) No 141/2013 is achieved. The proxy interview rate is 11.1%. 

EHIS wave 3

The precision requirements set out in the Annex II of the Commission Regulation (EU) No 2018/255 are achieved.

The proxy interview rate is 4.1%.

The standard error for 3 indicators was calculated.

• Relative share of respondents in good or very good health;
• Relative share of respondents with a longstanding illness or health problem;
• Relative share of respondents that were severely limited in activities people usually do because of health problems for at least the past 6 months.

Imputation techniques of missing values are not applied.

EHIS wave 2

Standard errors of key indicators

EHIS wave 3

Coverage errors:

A two stage stratified cluster sample on national and regional level is used. The sample is stratified by using the administrative regions in the country and persons' place of residence (town, village). As a result of the stratification 56 strata are designed. At the first stage clusters are selected with a probability proportional to their size, separately for 28 districts and for urban and village population. At the second stage, through a systematic selection households are identified. All persons aged 15 and over in selected households were interviewed. The survey applies the principle of the voluntary participation. A substitution is not allowed.

EHIS wave 1

By face to face interview (PAPI) 5 661 persons from 8 393 are interviewed. The response rate is 73.8%.

EHIS wave 2

By face to face interview (PAPI) 6 410 persons from 8 839 are interviewed. The response rate is 72.5%.

EHIS wave 3

By face to face interview (PAPI) 7 540 from 10 322 eligible persons are interviewed. The response rate is 73.0%.

In order to provide maximum opportunities for  analysing the data additional information is available:

• Original sample size (Eligible + Not eligible)
• Interviewed respondents - fully or partially completed questionnaire;
• Non-interviewed respondents - respondent was not found, refusal;
• Not eligible - deceased, does not live at the address, non-existent address / building / dwelling.

Population Census 2011 data base updated with deaths and births (annually) was used as sampling frame. In the list the information for households and household’s members is eligible. The list is updated annually based on current demographic statistics data as of 31 December. Although the population frame was updated with the latest results, there still were some shortcomings.

Not applicable.

Not applicable.

These are errors in the interview stage of collection of data, understanding of the issues by the respondents, sometimes wrong answers, and errors in data codification. The data entry program has been designed as to guarantee correctness and consistency of the data (logical controls, acceptable value, etc.), to be minimize this type of error. The program performs further checks for data accuracy with SPSS scripts.

In accordance with the methodological recommendations proxy interview is allowed only due to health problems of the respondent. There are two possibilities: either the respondent is unable to complete the interview due to physical or mental problems or when the person is hospitalized. Proxy interview was allowed limited to the questions specified in the Eurostat guidelines.

Methods used for reducing unit non-response 

1. The respondents’ address information was sent to the Regional Statistical Offices for checking after the sample selection.

2.Household invitation letter was prepared and signed by the President of the NSI. In this letter we explain the aim of the survey and how the sample was drawn. The importance to participate is stressed. The households were informed that the interviewers are staff of the Regional statistical offices and will identify himself (herself) by an identity card. We assure the persons that their answers will remain confidential.

3.Additional visits to the households - there were allowed second visits for the distant clusters and up to 4 visits in close clusters from the RSO location. 

Substitution is not allowed.

Non-response rate -  27.5%.

Data checking, cleaning and editing were done in accordance with the proposed by Eurostat guidelines and documents. Errors caused by the interviewers as well as errors introduced during data-entry were cleaned and edited. Many consistency checks are implemented in the data entry software, which are corrected simultaneously. Additional checks for logical consistence are carried out over the aggregated files. Data processing was performed with SPSS. 

Imputation techniques are not applied.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

T+11 months (preliminary data)

Final data will be disseminated following the validation procedure.

Preliminary data are available 11 months after the field work.

The final data are disseminated after finalization of data validation procedure by Eurostat. 

Micro-data are provided to Eurostat according to the European legislation.

The data for publishing statistical data is shown in the Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute.

Due to sample type of the survey, the data are representative at district level only for part of indicators.

International comparison - EHIS aims at achieving an input standardisation (questions, answers, filters, etc.) through conceptual translation into all EU languages. Each of the questions and response categories are accompanied by a detailed description, so that their meaning is identical in all Member States. Should be taken into account that not all countries have fully implemented the questionnaire or some questions were modified.

Not applicable.

Due to changing the EHIS questionnaire, some of the questions and indicators are partly or not comparable.

Not applicable.

Not applicable.

The coherence of the survey data and other official data sources was analysed as follow:

• morbidity - for selected diseases;
• discharges by diagnoses;
• mortality by causes;
• Health module applied in the Survey on Income and Living Conditions (SILC).

Not applicable.

Not applicable.

Press release.

EHIS - wave 1

Bulgaria - Statistical Panorama

Data on European health interview survey are available to all users of the NSI website under the heading Health - Health interview survey: http://www.nsi.bg/en/node/5630

Eurostat online database 

Not applicable.

Anonymised individual data can be provide for scientific and research purposes by individual request, according to the Rules for the provision of anonymised individual data for scientific and research purposes.

Information service on request, according to the Rules for the dissemination of statistical products and services in NSI.

Not applicable.

EHIS wave 1

• European Health Interview Survey questionnaire (2007-2009);
• Conceptual translation cards and guidelines;
• Quality Categories and Criteria for Delivery Data to EHIS;
• European Health Interview survey methodological sampling guidelines (Task force III report);
• Guidelines for the development and criteria for the adoption of Health Survey instruments.

EHIS wave 2

• European Health Interview Survey (EHIS wave 2), Methodological manual, Eurostat, 2013 edition;
• EHIS wave 2 Validation rules; 
• EHIS wave 2 Data delivery guidelines.

EHIS wave 3

• European Health Interview Survey (EHIS wave 3), Methodological manual, Eurostat, 2018 edition;
• EHIS wave 3 Validation rules.

100%

EHIS wave 1

Summary report on the application of criteria for quality assessment of the European Health Interview - Eurostat.

EHIS wave 2 and 3

Quality report

Not applicable.

• Law on Statistics;
• Regulation (EC) No 223/2009 on European statistics (recital 24 and Article 20(4)) of 11 March 2009 (OJ L 87, p. 164), stipulates the need to establish common principles and guidelines ensuring the confidentiality of data used for the production of European statistics and the access to those confidential data with due account for technical developments and the requirements of users in a democratic society.

Individual data are not published in accordance with article 25 of the Law on Statistics. The publishing of individual data can be performed only in accordance with article 26 of the same law.

For the purposes of dissemination of aggregated data the following rules are applied:

• An estimate should not be published if it is based on fewer than 20 sample observations or if the non-response for the item concerned exceeds 50%.
• An estimate should be published with a flag "low reliability" if it is based on 20 to 49 sample observations or if non-response for the item concerned exceeds 20% and is lower or equal to 50%.
• An estimate shall be published in the normal way when based on 50 or more sample observations and the item's non-response does not exceed 20%.