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1. Key messages

  • In Belgium, in 2018, strong socio-economic inequalities were observed in many health determinants. 
  • People with a low educational level (EL) were three times more likely to be daily smokers and twice more likely to be obese or daily consumers of sugary drinks than high educated people.
  • People with a low EL were also twice less likely to have a sufficient fruits/vegetables consumption or to practice enough physical activity as compared to high EL. 
  • Between 1997 and 2018, inequalities in daily smoking increased, while no clear trend was observed for inequality in the other health determinants studied.

2. Background

Socio-economic (SE) health inequalities refer to systematic disparities in health between SE groups, most often in disfavour of those on the lower position of the social and/or economic scale. SE health inequalities have been consistently observed in industrialized societies for the whole scope of health-related indicators, ranging from health determinants to mortality [1;2]. Tackling health inequalities is a priority for the WHO [3], the European Union [4], and for Belgium [5-7]. In order to assess progress towards reducing health inequalities, it is important to measure and monitor them [8,9].
Inequalities in health determinants have been computed from the data of the Health Interview Surveys 1997-2018. More information on the methodology can be found in this annexe. The health determinants chosen were daily smoking, obesity, performing at least 150 min of moderate to vigorous physical activity per week, daily consumption of at least 5 portions of fruits and vegetables, and daily consumption of sugar-sweetened beverages. The educational level (EL), grouped in three categories, was chosen as marker of socio-economic position to examine inequalities. 
Beside the prevalence rates by SE level, we also calculated the magnitude of the inequalities by computing three inequality indices: 
  • absolute and relative difference in age-adjusted rates between the low and the high ELs,
  • Population Attributable Fraction (PAF), i.e. the percentage of gain in health (or health determinant) expected in the whole population if all groups experienced the health (or health determinant) of the highest educated group.

3. Results

Situation in 2018

Daily smoking presents very large inequalities. While daily smokers represented 27.5% of the low educated group in 2018, they were only 9.4% in the high educated group. This represents an absolute difference of 18.1 percentage points (ppt), and a relative risk of almost 3, meaning that people with a low EL were three times more likely to smoke daily than the high educated people. If each EL had the level of smoking of the high educated people, the prevalence of smoking would decrease by 37.5% in the population.

The absolute difference in obesity prevalence between the low and high EL was 10 ppt, with people from the low EL being 1.8 times more likely to be obese than people with a high EL. The prevalence of obesity in the whole population would reduce by 22.7% if each EL had the same percentage of obesity as the high educated group.

Physical activity also shows very large inequalities; as it is a positive indicator for which we thrive for a higher prevalence, the values of the inequality indices are inversed, that is absolute inequalities will show values inferior to zero and relative inequalities values inferior to one. In 2018, 38.5% of high educated people practiced at least 150 min of moderate to vigorous aerobic physical activity per week, versus 18.8% in the low EL, representing an absolute difference of 19.7 ppt. People with a low EL were twice less likely to be physically active than people with a high EL. Bringing the physical activity practice of all ELs to the level of the high educated group would increase the physical activity practice by 23.9% at population level.

Large inequalities were also observed in nutrition. Twice more people were meeting the target of consuming 5 portions of fruits/ vegetables per day among people with a high EL than among those with a low EL, corresponding to an absolute difference of 8.4 ppt. Bringing the consumption of fruits/vegetables of all EL to the one of people in the high EL would increase the fruits/vegetable consumption in the whole population by 33.5%. People with a low EL were twice more likely to drink daily sugar-sweetened beverages than people from the high EL, the absolute difference between the 2 groups was 15.4 ppt. If people from all EL would reduce their consumption of sugar-sweetened beverages to the level of the high EL then the overall consumption level would decrease by 31.5%.

It is noteworthy that alcohol consumption does not present the same SE pattern as most health determinants. The SE pattern of excess consumption of alcohol is unclear and inconclusive.

Socio-economic inequalities in selected health determinants, Belgium, 2018
Source: Own calculation based on Health Interview Survey [10]
* statistically different from 0% for absolute difference and PAF, and statistically different from 1 for the relative difference (p<0.05)

Age-adjusted prevalence rate low EL Age-adjusted prevalence rate high EL Absolute difference
Relative difference PAF
Daily smoking (%people ≥ 15) 27.5% 9.4% 18.1%* 2.9* 37.5%*
Obesity (%people ≥ 18, BMI ≥ 30) 22.0% 12.0% 10.0%* 1.8* 22.7%*
At least 150 min of physical activity per week (%people ≥ 18) 18.8% 38.5% -19.7%* 0.5* -23.9%*
Daily consumption of 5 portions of fruits and vegetables (%people ≥ 6) 8.2% 16.6% -8.4%* 0.5* -33.5%*
Daily consumption of sugar-sweetened beverages (%people all age) 29.3% 13.9% 15.4%* 2.1* 31.5%*


The age-adjusted prevalence of daily smoking is decreasing between 1997 and 2018, but almost exclusively due to a strong decrease among people with a high EL, with few changes in the other ELs. Consequently, inequalities have clearly increased over time according to all three inequality indices (absolute, relative and PAF).

The age-adjusted prevalence of obesity increased between 1997 and 2018 in all ELs. A slight non-significant increase in absolute difference was observed, with no remarkable trends in relative inequality. The PAF decreased as the share of people pertaining to the low ELs (and with a high prevalence) has decreased.

The daily consumption of sugary drinks has decreased between 2013 and 2018 for all groups. We observe a slight non-significant decrease in absolute difference; the relative difference and PAF on the other hand remained constant.

The indicators used to assess physical activity and the consumption of fruits and vegetables in the HIS 2018 were new indicators, and therefore no trend can be described.

  • Daily smoking
  • Obesity
  • Sugary drinks
  • Absolute difference
  • Relative difference
  • PAF

Prevalence of daily smoking among people aged 15 and over, by educational level, Belgium, 1997-2018
Source: Own calculation based on Health Interview Survey, Sciensano [10]

Prevalence of obesity among people aged 18 and over, by educational level, Belgium, 1997-2018
Source: Own calculation based on Health Interview Survey, Sciensano [10]

Proportion of the population that drinks sugary drinks daily, by educational level, Belgium, 2013-2018
Source: Own calculation based on Health Interview Survey, Sciensano [10]

Absolute low-versus-high EL inequalities in health determinants indicators, Belgium, 1997-2018
Source: Own calculation based on Health Interview Survey, Sciensano [10]

Relative low-versus-high EL inequalities in health determinants indicators, Belgium, 1997-2018
Source: Own calculation based on Health Interview Survey, Sciensano [10]

PAF in health determinants indicators, Belgium, 1997-2018
Source: Own calculation based on Health Interview Survey, Sciensano [10]

4. Read more

View the metadata for this indicator

HISIA: Interactive Analysis of the Belgian Health Interview Survey


The Percentage-point (ppt) is the arithmetic difference between two percentages, for instance with 16% in group A and 8% in group B, the difference is 8 ppt, corresponding to a relative excess of 100%.


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Please cite this page as: Sciensano. Health Inequalities: Inequalities in health determinants, Health Status Report, 14 Feb 2022, Brussels, Belgium,