There are tons of statistical methods to get reasonable conclusions without an RCT. Some things can not be detected with an RCT, because the experiment is just impossible to run, so sometimes you need methods to do causal identification with observable data. Here you do not even need causal identification methods for observational data. You just need to do some descriptive statistics for a large group of people well to find interesting patterns. Whether this aging pattern in the mid-40s is causal it coincidental is not important at first. The pattern itself is interesting.