6.3 TB determinants

The tuberculosis (TB) epidemic is strongly influenced by social and economic development and health-related risk factors such as undernourishment, diabetes, HIV infection, alcohol use disorders and smoking. Achieving global targets for reductions in TB disease burden requires progress in addressing these determinants. For example, numbers of TB cases and deaths started to decline in western Europe, North America and some other parts of the world around the turn of the 20th century, as incomes grew, levels of poverty fell, and housing and nutrition improved (1, 2). The fastest declines in TB incidence and TB mortality in western Europe occurred in the 1950s and 1960s, in the context of progress towards universal health coverage (UHC), rapid social and economic development, and the availability of effective drug treatments.

The World Health Organization (WHO) has developed a framework for monitoring the Sustainable Development Goals (SDGs) related to TB. The framework comprises 14 indicators for which a relationship with TB incidence could be established, under seven SDGs (see Annex 6 of the main report). Five are health-related risk factors for TB and six are broader socioeconomic determinants; the other 3 indicators, for UHC and current health expenditures, are covered in Section 6.1.

There is a particularly clear relationship between TB incidence and (i) undernourishment and (ii) gross domestic product (GDP) per capita ( Fig. 6.3.1).

Fig. 6.3.1 The relationship between GDP per capita and the prevalence of undernourishment and TB incidence per 100 000 population, 2021 ^a

^a The year of data used for GDP per capita and undernourishment is the latest year for which data are available in the World Bank (https://data.worldbank.org/) and SDG (https://unstats.un.org/sdgs/dataportal) databases, respectively.

Globally in 2021, an estimated 2.2 million incident cases of TB were attributable to undernourishment, 0.86 million to HIV infection, 0.74 million to alcohol use disorders, 0.69 million to smoking and 0.37 million to diabetes (Fig. 6.3.2).

Fig. 6.3.2 Global estimates of the number of TB cases attributable to selected risk factors, 2021

Sources of data used to produce estimates were: Imtiaz S et al. Eur Resp Jour (2017); Hayashi S et al. Trop Med Int Health (2018); Lönnroth K et al. Lancet (2010); World Bank Sustainable Development Goals Database (http://datatopics.worldbank.org/sdgs/); WHO Global Health Observatory (https://www.who.int/data/gho); and WHO Global TB Programme.

There is considerable variation among countries in the relative importance and contribution of the five factors (Fig. 6.3.3), and thus also variation in which of these factors need to be prioritized as part of national efforts to reduce the burden of TB disease.

Fig. 6.3.3 Estimated percentage of incident TB cases attributable to five risk factors ^a at country level, 2021

(a) Undernourishment^b

(b) Alcohol use disorders

(c) HIV infection

(d) Diabetes^b

(e) Smoking

^a The percentages for alcohol use disorders, diabetes and smoking were calculated using incidence estimates restricted to adults aged ≥15 years.
^b WHO plans to commission systematic reviews to update estimates of the relative risk of TB associated with undernourishment and diabetes.

Variation in the relative contribution of five health-related risk factors to TB incidence is evident in the 30 high TB burden countries and 3 global TB watchlist countries (Fig. 6.3.4). Undernourishment is the leading contributor in most countries, although HIV infection is the top contributor in several African countries, especially in southern and east Africa.

Fig. 6.3.4 Estimated number of TB cases attributable to five risk factors, 30 high TB burden countries and 3 global TB watchlist countries,^a 2021

Best estimates (in colour) and uncertainty intervals (black) are shown. Blank areas (missing bars) represent no data available.

^a The three global TB watchlist countries are Cambodia, Russian Federation and Zimbabwe (see Annex 3 of the main report).
Sources of data used to produce estimates were: Imtiaz S et al. Eur Resp Jour (2017); Hayashi S et al. Trop Med Int Health (2018); Lönnroth K et al. Lancet (2010); World Bank Sustainable Development Goals Database (http://datatopics.worldbank.org/sdgs); WHO Global Health Observatory (https://www.who.int/data/gho); and WHO Global TB Programme.

As with health-related risk factors for TB, there is considerable variation by country in the status of other TB determinants, including access to clean fuels, income inequality, poverty, social protection and housing conditions (Fig. 6.3.5).

Fig. 6.3.5 Status of selected SDG indicators beyond SDG 3 at country level, latest available year

(a) Access to clean fuels

Map for selected SDG indicators beyond SDG 3 in high TB burden countries - a

(b) Income inequality

Map for selected SDG indicators beyond SDG 3 in high TB burden countries - b

(c) Living in poverty

Map for selected SDG indicators beyond SDG 3 in high TB burden countries - c

(e) Living in slums

Map for selected SDG indicators beyond SDG 3 in high TB burden countries - e

(f) Undernourishment

Access to clean fuels: Percentage of population with access to clean fuels and technologies for cooking.
Income inequality: GINI index is shown where 0 is perfect equality and 100 is perfect inequality.
Living in poverty: Percentage of population living below the international poverty line, which is defined e.g. living on $1.90 per day (at 2017 purchasing power parity).
Access to social protection: Percentage of population covered by social protection and labour programmes.
Living in slums: Percentage of urban population living in slums.
Undernourishment: Percentage of population undernourished.
Source: World Bank Sustainable Development Goals Database ( http://datatopics.worldbank.org/sdgs/)

The most recent data for undernourishment and five socioeconomic indicators associated with TB incidence for the 30 high TB burden countries and three global TB watchlist countries are shown in Fig. 6.3.6. In this figure, the outer edge of the circle (100) is the ideal value for each indicator. To represent this situation visually, the indicators “proportion of the urban population living in slums” and “proportion of the population living below the international poverty line” are inverted.

All indicator values in the figure are for the general population as opposed to people with TB; values for TB patients specifically (e.g. out-of-pocket expenditure and access to social protection) may differ from these general values.

Based on the latest available data in the World Bank database, some upper-middle-income and lower-middle-income countries (e.g. Brazil, China, India, Indonesia, Mongolia, South Africa, Thailand, and Viet Nam) appear to be performing relatively well. However, progress is likely to have been set back by the COVID-19 pandemic. Even before the pandemic, other high TB burden countries already faced major challenges in achieving a range of TB-related SDG targets. Moreover, values for poor populations and vulnerable groups most at risk of developing TB are likely to be worse than national averages. Addressing broader determinants of the TB epidemic requires multisectoral action and accountability. Global and national progress in adapting and using the WHO multisectoral accountability framework for TB (MAF-TB) is one of the featured topics) of this report.

Fig. 6.3.6 Status of selected SDG indicators beyond SDG 3 in 30 high TB burden and 3 global TB watchlist countries, latest available year

Clean fuels: Percentage of population with access to clean fuels and technologies for cooking.
Income equality: An inverse GINI index is shown where 0 is perfect inequality and 100 is perfect equality.
Not in poverty: Percentage of population living above the international poverty line, which is defined e.g. living on $1.90 per day (at 2017 purchasing power parity).
Not in slums: Percentage of urban population not living in slums.
Social protection: Percentage of population covered by social protection and labour programmes.
Nutrition: Percentage of population not undernourished.
Source: World Bank Sustainable Development Goals Database (http://datatopics.worldbank.org/sdgs/).

Further country-specific details for the 14 indicators related to TB incidence are available in the Global tuberculosis report app and Country profiles.

Note: Estimates of TB cases attributable to smoking shown in figures 6.3.2, 6.3.3(e) and 6.3.4 were updated on 9 November 2022.

References

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