This study investigated the contribution of dataset reuse to the diversity of research areas using articles that reused datasets. The Framingham Heart Study (FHS) and Atherosclerosis Risk in Communities Study (ARIC), which are widely used in life sciences, were selected as samples. Disease names in the articles that reused these datasets were extracted based on Medical Subject Headings (MeSH) descriptors. The frequencies of disease names were examined from the 1950s for FHS and the 1980s for ARIC. The amount of “cardiovascular diseases” research was decreasing, while that of “pathological conditions, signs, and symptoms” was increasing from the beginning. The Herfindahl-Hirschman Index (HHI) scores, which are an index of diversity, were calculated based on disease names; these scores indicate that research areas have diversified over time. This study found the HHI and MeSH descriptors could be used to measure the contribution of dataset reuse to the diversity of research areas.