\documentclass[a4paper,12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{csvsimple}
\usepackage{geometry}
\usepackage{array}
\usepackage{longtable}
\usepackage{anyfontsize}
\usepackage{xcolor}
\usepackage{colortbl}

\geometry{a4paper, margin=0in}

% Define light grey color
\definecolor{lightgrey}{gray}{0.9}
\begin{document}

\begin{center}
\renewcommand{\arraystretch}{1.6}
\bfseries
\fontsize{40}{50}\selectfont % Set font size to 50pt, line spacing to 60pt
\begin{longtable}{>{\centering\arraybackslash}p{\textwidth}}    
\\[20pt]
\csvreader[head to column names]{Ruder-IDs.csv}{}{\csvcoli \\[20pt] \arrayrulecolor{lightgrey}\hline \\[20pt]}
\end{longtable}
\end{center}

\end{document}