1. Scoping review
The scoping review focused on differences in the obtained prevalence estimates for obesity, hypertension, diabetes, and asthma when derived from different data sources for same population (Appendix 1). Observed differences between data sources varied by health outcomes (Figure 1.).
For obesity, several studies have demonstrated that prevalence based on self-reported height and weight tends to be lower when compared to prevalence based on measured data, usually from health examination surveys. 19,20,21,22,23,24 When comparing self-reported results with those obtained from medical registers results are inconclusive, i.e. there is indication that self-reported obesity prevalence would be higher25 and other studies show similar results between these two sources32. Measured obesity prevalences tend to be higher when compared to data from medical records.32
For hypertension, prevalence based on self-reported information tends results lower prevalence of hypertension in comparison to data obtained through objective survey measurements of blood pressure.21,26,27,28 When results based on self-reported information are compared to register based information, some studies are reporting lower results26,29,30,31,32 , and some higher resutls25,33,34,35,36. For measured hypertension, higher results is often observed in comparison to medical records.29,32
For diabetes, in some studies, self-reported information has provided lower diabetes prevalence than prevalence based on objective survey measurements21,31 and also self-reported diabetes prevalence has been higher than what has been obtained from medical records37.
For asthma, limited number of studies comparing the prevalence among adults through different data sources was available even though there were several studies focusing on paediatric asthma. Among adults, reported results indicate that prevalence of asthma based on serf-repoted information is lower in comparison to medical records.34,31,36,38,39
2. International health related database
Reviewing four different international databases (ECHI data tool, WHO Global Observatory data repository, WHO Europe Health for All Database, and OECD database) which cover health indicators, we evaluated the definitions used of these indicators, the data sources these indicators were calculated from, and how actual reported prevalences by European Union (EU) Member States (MSs) differed.
Only the ECHI data tool covered all four indicators (obesity, hypertension, diabetes, and asthma), generally results were presented for age group 18+ years, except in the OECD database which presented results for age group 15+ years. Only the ECHI data tool used systematically data from the European Health Interview Survey for all four indicators, i.e. self-reported data. In other databases, data sources varied between indicators but also within indicators between countries. (Table 2).
Table 2.
Data sources, coved age group and used indicator definitions in four international health databases
|
Database
|
ECHI data tool
|
WHO Global Health Observatory
|
WHO European Health for All Database
|
OECD database
|
Data source
|
European Health Interview Survey
|
For obesity and hypertension data from population-based surveys was used, and for diabetes various available data sources were used. Calculations were supplemented with modelling if a country did not have the required data.
|
For BMI data from the WHO Global Health Observatory, for diabetes data sources vary between countries covering health interview or examination surveys, medical prescriptions, medical reimbursements, diabetes registers, out-patient records, hospital discharge data, and health insurance records individually or in varying combinations.
|
Sources vary
|
Age group covered
|
18+
|
18+
|
18+
|
15+
|
Indicator
|
Obesity
|
BMI ≥ 30 kg/m2 based on self-reported data from the European Health Interview Survey
|
BMI ≥ 30 kg/m2 based on measured height and weight
|
BMI ≥ 30 kg/m2 based on measured height and weight
|
Both self-reported and measured information for combined overweight and obesity BMI ≥ 25 kg/m2
|
Hypertension
|
Self-reported, having raised blood pressure in past 12 months
|
Measured systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg
|
Not available
|
Not available
|
Diabetes
|
Self-reported, having diabetes in the past 12 months
|
Raised fasting blood glucose ≥ 7.0 mmol/l or on medication
|
ICD-9: 250; ICD-10: E10-E14
|
Not available
|
Asthma
|
Self-reported, having asthma in the past 12 months
|
Not available
|
Not available
|
Not available
|
When the actual prevalence estimates at the country level within EU MSs were compared between different international databases, we observed substantial differences (Figure 2.). For comparisons year 2014 was selected since in all databases data for this year was available.
When comparing prevalences presented in different databases (Appendix 2), we observed differences, even though results represent the same age group and year. The OECD data cannot be directly compared with other databases since it covered a different age group and presented prevalence for overweight or obesity instead of obesity only.
For the prevalence of obesity and hypertension, the WHO Global Health Observatory numbers tend to be little higher than those reported in the ECHI data tool which can be explained by different data sources. For diabetes, the difference is more divided.
3. Case study from Finland
Obesity and elevated blood pressure or hypertension, were two indicators which had major differences between data sources. For obesity, prevalence ranged from 2.7% in register-based data to 26.1% when survey data (self-reported or measured) was used, and for hypertension from 16.8% to 45.5%. For diabetes and asthma, the obtained prevalences were rather similar between the data sources. (Table 3.)
Table 3.
Prevalences of obesity, high blood pressure, diabetes, and asthma by different data sources in the Finnish case study
Indicator
|
Data source
|
Self-reported information on survey questionnaire
|
Objective measurement during the health survey
|
Self-reported or measured in survey
|
Register based data
|
Obesity
|
21.7%
|
25.4%
|
26.1 %
|
2.7%
|
Elevated blood pressure or hypertension
|
24.2%
|
35.5%
|
45.5%
|
16.8%
|
Diabetes
|
7.1%
|
6.1%
|
8.9%
|
8.5%
|
Asthma
|
8.9%
|
-
|
8.9%
|
9.5%
|
*For register and survey data
Looking at the population level, prevalence of different indicators does provide only one perspective to the comparability of different data sources. It does not tell how much of all the identified cases can be obtained from a specific data source. The agreement of register and survey data in the individual level varied from k = 0.11 for obesity to k = 0.83 for diabetes. (Table 4.)
Table 4.
Data source for identified cases in the Finnish case study
Indicator
|
Total number of identified cases
|
Cases identified by
|
Kappa*
|
Only survey data (self-reported and/or measured), n (%)
|
Only register data, n (%)
|
Both survey and register data, n (%)
|
Obesity
|
1590
|
1451 (91.3%)
|
14 (0.1%)
|
125 (7.9%)
|
0.11
|
Elevated blood pressure or hypertension
|
3020
|
1906 (63.1%)
|
60 (2.0%)
|
1054 (34.9%)
|
0.33
|
Diabetes
|
652
|
119 (18.3%)
|
58 (8.9%)
|
475 (72.9%)
|
0.83
|
Asthma
|
674
|
120 (17.8%)
|
157 (23.3%)
|
397 (58.9%)
|
0.72
|
*For register and survey data
For obesity, 91% of all cases were identified only by survey data, i.e. those persons did not have any diagnoses in the administrative registers about obesity, 8% were identified as obese by both survey and register, data and only 0.1% had obesity related diagnose but were not identified as obese based on self-reported or measured BMI in the survey.
Also, for hypertension or elevated blood pressure, the majority of the cases were observed in the survey data. Almost 2/3 of all cases were identified only by survey data, 1/3 by both survey and administrative register data, and only few cases (2.0%) were identified only by register data.
For diabetes and asthma, for which at the population level prevalence provided rather similar results between different data sources, we can see that for only 59% of asthma and 73% of diabetes cases were identified by both survey data as well as through administrative registers. For diabetes, most of the additional cases (18%) come from survey data while for asthma, 23% of cases come only from the administrative register data.