Conception and design: Beaumont, Smyth. Acquisition of data: Beaumont, Godzik. Analysis and interpretation of data: all authors. Drafting the article: Beaumont, Godzik. Critically revising the article: Beaumont, Dahiya, Smyth. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Beaumont. Study supervision: Smyth.