a decreasing trendP -value < 0.001
For instance, the estimates for the first cluster (intercept = 2330.26, slope = -128.2) reveal that the initial rate of urolithiasis in the countries including this cluster, Afghanistan, Andorra, and Comoros, has been 2330.26 per 100000 in 1990, and it has a decreasing trend with a slope of -128.2 until 2019, every two years ( P -value < 0.001).