  Biological age is an important sociodemographic factor in studies on academic
careers (research productivity, scholarly impact, and collaboration patterns).
It is assumed that the academic age, or the time elapsed from the first
publication, is a good proxy for biological age. In this study, we analyze the
limitations of the proxy in academic career studies, using as an example the
entire population of Polish academic scientists visible in the last decade in
global science and holding at least a PhD (N = 20,569). The proxy works well
for science, technology, engineering, mathematics, and medicine (STEMM)
disciplines; however, for non-STEMM disciplines (particularly for humanities
and social sciences), it has a dramatically worse performance. This negative
conclusion is particularly important for systems that have only become recently
visible in global academic journals. The micro-level data suggest a delayed
participation of social scientists and humanists in global science networks,
with practical implications for predicting biological age from academic age. We
calculate correlation coefficients, present contingency analysis of academic
career stages with academic positions and age groups, and create a linear
multivariate regression model. Our research suggests that in scientifically
developing countries, academic age as a proxy for biological age should be used
more cautiously than in advanced countries: ideally, it should be used only for
STEMM disciplines.
