The growth of acronyms in the scientific literature

Abstract

Some acronyms are useful and are widely understood, but many of the acronyms used in scientific papers hinder understanding and contribute to the increasing fragmentation of science. Here we report the results of an analysis of more than 24 million article titles and 18 million article abstracts published between 1950 and 2019. There was at least one acronym in 19% of the titles and 73% of the abstracts. Acronym use has also increased over time, but the re-use of acronyms has declined. We found that from more than one million unique acronyms in our data, just over 2,000 (0.2%) were used regularly, and most acronyms (79%) appeared fewer than 10 times. Acronyms are not the biggest current problem in science communication, but reducing their use is a simple change that would help readers and potentially increase the value of science.

Keywords: acronyms; communication; knowledge; meta-research; none; scientific publishing; scientific writing.

Figure 1.. Mean proportions of acronyms in titles and abstracts over time.

The proportion of acronyms (purple line) has risen steadily over time in abstracts both for acronyms that are letters and/or numbers (top left) or just letters (top right). Acronyms are generally less common in titles than abstracts, and the proportion in titles has been relatively stable since 2000, but there was an increase from 1960 to 2000 (bottom left and right). Three-character acronyms (blue lines) are more common than two-character acronyms (brown-orange lines) and four-character acronyms (olive green lines) in both titles and abstracts. A sufficient number of abstracts only became available from 1956. The spikes in titles for acronyms of length 2+ in 1952 and 1964 are because of the relatively small number of papers in those years, with over 78,000 papers being excluded in 1964 because the title was in capitals.

Figure 1—figure supplement 1.. Mean proportions of acronyms in titles and abstracts over time, with the 100 most popular acronyms excluded.

Each line shows the trend after excluding up to the n most popular acronyms (n = 1, ..., 100). The darkest line is for n = 1, and the lightest line is for n = 100. The number of titles and journals in the early 1950s is much smaller, hence the more erratic trend for titles in that decade.

Figure 1—figure supplement 2.. Mean proportions of acronyms in titles and abstracts over time by article type.

Data for six article types (journal article, clinical trial, case report, comment, editorial, and other). The high proportion of acronyms in the 1950s and 1960s for ‘other’ is driven by a relatively large number of obituaries that include qualifications, such as FRCP (Fellow of the Royal College of Physicians) or DSO (Distinguished Service Order). The drop in the proportion of acronyms in 2019 for ‘clinical trials’ and ‘other’ may be due to a delay in papers from some journals appearing in PubMed.

Figure 1—figure supplement 3.. Mean proportions of acronyms in titles over time by article type with a truncated y−axis.

Using a truncated y−axis more clearly shows the upward trend in the use of acronyms in titles for all article types over time (by reducing the influence of ‘other’ in the 1950s and 1960s; see Figure 1—figure supplement 2).

Figure 2.. Estimated time to re-use of acronyms over time.

The solid line is the estimated time in years for 10% of newly coined acronyms to be re-used in the same journal. 10% was chosen based on the overall percentage of acronyms being re-used within a year. Newly coined acronyms are grouped by year. The dotted lines show the 95% confidence interval for the time to re-use, which narrows over time as the sample size increases. The general trend is of an increasing time to re-use from 1965 onwards, which indicates that acronyms are being re-used less often. The relatively slow times to re-use in the 1950s and early 1960s are likely due to the very different mix of journals in that time.

Figure 3.. Average number of words in abstracts and titles over time.

The average title length has increased linearly between 1950 and 2019 (left). The average length of abstracts has also increased since 1960, except for a brief reduction in the late 1970s and a short period of no change after 2000 (right). A sufficient number of abstracts only became available from 1956. Note that the y-axes in the two panels are different, and that neither starts at zero, because we are interested in the relative trend.