Stratification by geographical region, age, disease severity, TSLP determination method, sample size, and study quality revealed significantly elevated TSLP levels in European AD patients (SMD = 3.48, 95% CI 1.75–5.21, p < 0.0001), adult AD patients (SMD = 4.10, 95% CI 2.00–6.21, p < 0.0001), child AD patients (SMD = 0.83, 95% CI 0.08–1.59, p = 0.031), and all severity groups with AD compared with the control group (mild: SMD = 1.15, 95% CI 0.14–2.16, p = 0.025; moderate: SMD = 2.48, 95% CI 0.33–4.62, p = 0.024; and severe: SMD = 8.28, 95% CI 4.82–11.74, p = 2.72e−6). The gene discussed is TSLP; the disease is Alzheimer disease.