the standardized PRS for population k, and wϕ,k is the regression coefficient. We screened four different ϕ values, 10−6, 10−4, 10−2 and 1.0, in this work. The ϕ value and the corresponding regression coefficients for the linear combination of PRS that maximized the R2 in the validation dataset were used in the testing dataset to calculate the final PRS: PRS=w^ϕ^,1PRSϕ^,1+w^ϕ^,2PRSϕ^,2+⋯+w^ϕ^,KPRSϕ^,K.
