A review of the historical use of sex as a biological variable in the .

Despite National Institute of Health (NIH) mandates requiring sex as a biological variable (SABV), female underrepresentation persists in research, driving the to publish SABV expectations in 2021. To determine progress within the , this mini-review evaluated SABV during the first 6 mo of each decade from 1980 to 2020, and 2019, to mitigate pandemic influence. Of the 1,205 articles published, 1,087 articles were included in this review (articles without original research subjects were excluded), of which 72.9% identified subjects. There were consistently fewer female human participants than males, except within 2019 (1980: females = 3, males = 5; 1990: females = 70, males = 199; 2000: females = 305, males = 355; 2010: females = 186, males = 472; 2019: females = 1,695, males = 1,550; 2020: females = 1,157, males = 1,222) and fewer female animals than males (1980: females = 58, males = 1,291; 1990: females = 447, males = 2,628; 2000: females = 590, males = 3,083; 2010: females = 663, males = 4,517; 2019: females = 338, males = 1,340; 2020: females = 1,372, males = 1,973). Only 16 (12.3%) articles including humans discussed SABV from 1980 to 2020. There are persistent SABV disparities within with some improvements in recent years. It is imperative that organizations such as the American Physiological Society and NIH foster an expectation of SABV as the norm, not the exception.