struggling with biostat and association study designs.
I initially wanted to do an association study comparing two populations and seeing which SNPs are significant. For example, I am looking at just variation between centenarians (people who live >100years) and a control group. Should I be including age as a covariate? I am interested in detecting longevity variants or anything that suggests a difference from the control group. I do not think age would be necessary since it is not a confounder because it is not an indepedent covariate. I think I was reading that adding independent covariates can decrease power of the study.
When do you guys start considering modeling with linear or logistic regressions instead of GWAS? Is it when you have a depedent variable and a predictor variable you are interested in? Would you guys think I should have added covariates?
Or is another way possible to change the case and control population to groups that reflect covariate status? For example, If I was interested in centenarians with alzheimers compared to a control population with alzheimers, a logistic regression with Alzheimer status be more appropriate than running a GWAS on them?
Sorry for so many questions.