I look forward to the 2021 Tokyo Olympic Games with some degree of excitement and apprehension. The 2021 Tokyo Olympic Games will be like none in the history of the modern Olympics. It is important to remember that this is not Tokyo’s first, but its second Olympic Games. The first Olympic Games held in Tokyo occurred in 1964. As part of the 1964 Olympic Games, the International Olympic Committee (IOC) proposed to conduct a research study on the lifelong health and physical strength of Olympic athletes who participated in the 1964 Olympic Games. Twenty-three countries and 1110 Olympic athletes participated in this study designed to explore the association between physical strength and skilled performance. Data was collected between July and September 1964 and included questionnaires on lifestyle (history of drinking, history of smoking), as well as physical fitness measures (including height, weight, right and left handgrip strength, systolic blood pressure, and diastolic blood pressure) (Takeuchi et al., 2021).  The research project ended in 1972, but Japan continued to collect on the 355 (295 men, 60 women) Japanese athletes who had participated in the 1964 Tokyo Olympic Games. Recently, the Japan Sport Association (JSPO) collected survival data on these 1964 Japanese Olympians including date of latest confirmation of survival (for Olympians whose vital status was ‘alive’), and date of death (for Olympians whose vital status was ‘dead’). Of the original 355 Japanese Olympic Athletes tested in 1964 the researchers were able to verify the status of 342 (283 men, 59 women) athletes, deaths were confirmed for 70 (64 men, 6 women) athletes between September 1964 and December 2017(Takeuchi et al., 2021). 
A recent study found Japanese Olympic athletes who participated in the 1964 Tokyo Olympic Games lived longer than the Japanese general population. The authors (Takeuchi et al., 2021) reported that body mass index (BMI: weight in kilograms divided by height in meters squared) ≥25 kg/m2 was significantly associated with higher mortality, whereas smoking history or handgrip strength was not associated with mortality among Olympic athletes. The fact that BMI was associated with mortality was not surprising given a number of studies have reported an association between BMI and all-cause mortality (Matsuo et al., 2008; Sasazuki et al., 2011; Park et al., 2012; Aune et al., 2016). 

The authors (Takeuchi et al., 2021) also point out a limitation of this study was that BMI does not differentiate between fat and muscle masses. Therefore, the higher BMI among the 1964 Tokyo Japanese Olympic athletes may be explained by a larger amount of muscle mass rather than a larger amount of fat mass. It is not uncommon for athletes to have a higher degree of muscle mass than the normal population giving them a higher BMI (Jonnalagadda et al., 2004). It is also possible, that a higher mortality among athletes with BMI≥25 kg/m2 in this study population may be explained by characteristics of sports disciplines that require large muscle mass. Advanced body composition methods such as dual X-ray absorptiometry (DXA), which can not only determine fat and muscle masses but also bone mass as well as bone mineral density would be informative.  The restrictions placed on the current Tokyo Olympics due to the COVID-19 pandemic limit the research that can be done on athletes at this Olympics.  Hopefully, the next Olympics Games will offer the opportunity for future studies and the role of body composition on morality in these elite athletes. Regardless I will be watching these Tokyo Olympics and cheering on these elite athletes.

Reference
Aune D, Sen A, Prasad M, et al. Bmi and all cause mortality: systematic review and non-linear dose-response meta-analysis of 230 cohort studies with 3.74 million deaths among 30.3 million participants. BMJ 2016;353:i2156.

Jonnalagadda SS, Skinner R, Moore L. Overweight athlete: fact or fiction? Curr Sports Med Rep 2004;3:198–205.

Matsuo T, Sairenchi T, Iso H, et al. Age- and gender-specific BMI in terms of the lowest mortality in Japanese general population. Obesity 2008;16:2348–55.

Park S-Y, Wilkens LR, Murphy SP, et al. Body mass index and mortality in an ethnically diverse population: the Multiethnic cohort study. Eur J Epidemiol 2012;27:489–97.

Sasazuki S, Inoue M, Tsuji I, et al. Body mass index and mortality from all causes and major causes in Japanese: results of a pooled analysis of 7 large-scale cohort studies. J Epidemiol 2011;21:417–30.

Takeuchi T, Kitamura Y, Ishizuka S, et al. Mortality of Japanese Olympic athletes in 1964 Tokyo Olympic Games. BMJ Open Sport & Exercise Medicine 2021;7:e000896. doi:10.1136/ bmjsem-2020-000896

About the Author
Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise and body composition testing for researchers across the University of Minnesota.