Senior elite swimmers were top-10% youths: A Swedish population cohort study

We evaluated how well swimming performance at ages 13-15 identified future senior elite status (ages 22-25) in a non-selected national cohort. Using the Swedish federation's Tempus Open database, we followed 8,965 Swedish-developed swimmers born 1995-2001. Each swimmer's youth performance was summarized as the maximum within-cohort percentile across ages, events, and pool lengths; the resulting top-10%-in-any-cell filter retained approximately 19% of the cohort. Senior elite was defined as World Aquatics points $\ge$ 750 at ages 22-25. All 41 swimmers reaching this level (15 women, 26 men) had been in the top 10% of at least one youth cohort (95% CI: 78.2-100 women, 86.8-100 men), but only 1.5-3.7% of retained swimmers later reached senior elite. Observed capture remained 100% in an age 16-18 sensitivity analysis among members of the original cohort still observed at those ages. The pattern was also unchanged under alternative senior thresholds, cohort restrictions, and senior sub-windows, while narrower event and pool definitions reduced capture. Early performance therefore functioned as a permissive monitoring filter in this cohort, not a precise individual-selection tool.