This heat map shows the distribution of input sources used for the Global Burden of Disease (GBD) 2021 low back pain (LBP) estimates across the 27 European Union countries. Each country is shaded according to a colour: light green represents 1–5 sources, medium green 6–10 sources, darker green 11–15 sources, and the darkest green 16–20 sources. Countries contributing the most sources include Spain (18), Sweden (17), and Germany (16), while those with the fewest include Cyprus (1), Bulgaria (2), Malta (3), and Romania (3). Most countries contributed between 5 and 10 sources, showing moderate representation across the EU.