Region-specific latitudinal gradients, in original and current study
| Age-standardised prevalence estimates | Midpoint latitude* | Original data set, slope in 2009 (95% CI) | Current analysis, slope in 2009 (95% CI) | Current analysis, slope in 2018 (95% CI) | |
| Australasia | 28 | 35.67 | 8.38 (5.77 to 10.98 ) | 7.97 (4.97 to 10.98 ) | 11.05 (5.96 to 16.15 ) |
| Western Europe | 155 | 47.88 | 8.11 (3.85 to 12.35 ) | 2.75 (1.04 to 4.46 ) | 3.77 (1.28 to 6.25 ) |
| UK/Ireland | 23 | 53.43 | 19.81 (7.11 to 32.51 ) | 16.86 (5.93 to 27.78 ) | 19.60 (6.80 to 32.40 ) |
| Scandinavia/North Atlantic | 42 | 62.75 | −4.29 (−7.59 to −0.99 ) | −1.39 (−4.01 to 1.23) | −1.41 (−4.17 to 1.34) |
| Atlantic Coast/Central Europe | 47 | 43.93 | 2.82 (0.42 to 5.21 ) | 13.12 (7.40 to 18.83 ) | 17.59 (8.51 to 26.67 ) |
| Italian region | 43 | 41.56 | −11.59 (−20.17 to −3.02 ) | −10.33 (−17.48 to −3.17 ) | −15.58 (−26.90 to −4.26 ) |
| Eastern Europe | 57 | 51.44 | −0.76 (−4.67 to 3.15) | −0.20 (−5.06 to 4.66) | −0.27 (−6.86 to 6.33) |
| North America | 32 | 43.84 | 15.35 (6.37 to 24.32 ) | 13.98 (7.67 to 20.30 ) | 17.80 (8.60 to 26.99 ) |
| Latin America and Caribbean | 5 | 16.25 | 0.06 (−1.56 to 1.68) | 0.12 (−0.46 to 0.70) | 0.03 (−0.26 to 0.31) |
| Middle East and Africa | 19 | 32.12 | 1.62 (−4.26 to 7.50) | 0.93 (−2.40 to 4.25) | 0.86 (−2.07 to 3.79) |
| Asia and Pacific | 8 | 33.55 | 0.90 (−3.24 to 5.03) | 0.37 (0.34 to 0.40 ) | 0.08 (0.06 to 0.09 ) |
Slope (95% CI) represents change in prevalence per 100 000 persons per degree latitude at specified latitude. Results in boldface denote statistical significance (p<0.05). All analyses adjusted for prevalence year, use of systematic diagnostic criteria and inclusion of possible cases. Study prevalence estimates time-corrected to 2009.
*Midpoint latitude estimated as the mean of the maximum and minimum latitude of the prevalence points within the specified region.