| Sleep and related disorders | 26 |
| History of Science and Medicine | 18 |
| Diverse Historical and Scientific Studies | 14 |
| Historical Studies and Socio-cultural Analysis | 13 |
| Sleep and Work-Related Fatigue | 10 |
| Race, History, and American Society | 7 |
| Historical Geopolitical and Social Dynamics | 7 |
| Vietnamese History and Culture Studies | 6 |
| Sleep and Wakefulness Research | 6 |
| Soviet and Russian History | 6 |
| Dementia and Cognitive Impairment Research | 5 |
| Alzheimer's disease research and treatments | 5 |
| Urban, Neighborhood, and Segregation Studies | 4 |
| Food Security and Health in Diverse Populations | 4 |
| History of Science and Natural History | 4 |
| Urban Transport and Accessibility | 4 |
| Species Distribution and Climate Change | 4 |
| Homelessness and Social Issues | 4 |
| HIV, Drug Use, Sexual Risk | 4 |
| American Environmental and Regional History | 4 |