Life Expectancy of the Tokugawa Shogun Family Estimated from Edo Period Historical Records

Previous Reports on Edo People’s LE

To date, there have been several reports on the LE of Japanese populations prior to the 20th century, covering various groups. In summary, Kobayashi18) estimated the LE for males and females in Toraiwa Village (during the late Edo period) to be 36.8 years and 36.5 years, respectively. In his study, an individual's birth year was set to age 0 using a simple method that downgraded traditional age 1 to age 0. Hayami19) used Edo-period documents (Shumon-Ninbetsuaratame-cho) to estimate the LE of people at the time. While he was unable to calculate LE at birth, he reported the LE at age 2 as 32.0 years for males and 30.0 years for females. Narimatsu15) reported a LE of 37.7 years for males and 36.4 years for females in Niida Village, and a LE of 44.7 years for males and 43.3 years for females in Shimomoriya Village.20) Kalland and Pedersen21) reported an average LE of 44.7 years for males and 43.3 years for females in Senpukuji Village. Based on these reports, the average LE for Edo-period populations is generally estimated to have been in the late 30s to early 40s.

In this study, we estimate that the LE at birth for the Tokugawa Shogun family was around 20 years (male, 20.93 years; female, 20.53 years). This finding is particularly intriguing because the Tokugawa Shogun family was at the height of political and economic power during the Edo period. Given their superior standard of living compared to ordinary people, it is unusual that they might have had a shorter life expectancy than commoners of the time.

However, there are important considerations when comparing our Tokugawa data to previous reports. One key factor is the different methods of age calculation. Traditionally, in Japan, a person’s age was counted as 1 at birth. In the Edo period, according to the lunar calendar, the most significant issue is that there was no concept of "age 0"; individuals were considered to be 1 year old at birth.22) As a result, the life expectancy of Edo-period people may have been overestimated in previous studies. This not only complicates comparisons with modern populations, but also introduces potential inaccuracies in paleodemographic analyses. In our study, we estimate LE by converting all birth dates to the solar calendar and treat the birth year as age 0. We believe this approach largely corrects the errors in previous studies, providing a more accurate representation of life expectancy.

Comparison to Modern Japanese old population

According to the Simple Life Tables published by the Ministry of Health, Labour and Welfare (2023), the LE of modern Japanese is 81.09 years for males and 87.14 years for females, among the highest in the world. The infant mortality rate in modern Japan is approximately 0.2%, meaning about 1.8 deaths per 1,000 live births occur before the age of 1 year.23)

In our study, the infant mortality rate for the Tokugawa Shogun family was much higher: 31.33% for males and 33.85% for females by the end of age 0 (Table 3). This translates to roughly 313 male deaths and 339 female deaths per 1,000 live births before the age of 1. The high infant mortality rate during the Tokugawa period suggests that such rates were likely consistent across pre-modern Japan, as clearly illustrated in the report by Kobayashi.18) In his study, the mortality rates for Toraiwa Village, Nagano Prefecture, during the late Edo period were 49.4% for males (at age 4) and 50% for females (at age 3), indicating that half of all children born in the Edo period did not survive past age 3 or 4.

Following this early period of very high infant mortality, individuals from the Tokugawa Shogun family seem to experience a slower decline in survival rates up to age 10, with the trend continuing into their 70s and 80s (Fig. 1). Since the survival curve after age 10 is nearly linear with a gradual downward slope, it suggests that the mortality rate remained relatively stable throughout this period. According to the classification of survival curves by Pearl and Miner,24) the Tokugawa Shogun family’s survival curve resembles a Type III curve from age 0 to 3 and a Type II curve after age 10. In summary, the death rates of the Tokugawa Shogun family after age 10 were significantly lower than during their infancy.

Causes of Death

In this study, the Tokugawa Shogun family exhibited a lower mortality rate in winter and a higher rate in summer. This pattern is likely due to the fact that, while they were able to stay warm in the elaborately constructed Edo Castle during the winter months, there were no measures to address the heat during the summer. According to Kito,25) in his study of farmers in the Edo and Meiji periods, digestive system diseases were the most common cause of death in summer, while cold weather-related illnesses were the leading cause of death in winter. The causes of death within the Tokugawa Shogun family may not have differed significantly from Kito’s findings. Additionally, it can be inferred that specific causes of death for the Tokugawa Shogun family likely included respiratory infections, bacterial and viral diarrhea, parasitic diseases, and other health issues prevalent throughout the year.2,12,26)

We also consider lead poisoning as a potential cause of death for the Tokugawa Shogun family. Anthropological studies suggest that high-ranking individuals in Edo-period Japan may have been exposed to elevated levels of lead.27-29) But where did this high level of lead come from? One likely source is the cosmetics used during the Edo period. White makeup powder (Oshiroi; 白粉), which is thought to have originated in China, began to be used in Japan as early as the Asuka-Nara period. During the Keicho period (1596–1615), the production of white makeup powder became widespread in Sakai City30) and continued to be used by the Japanese population until the 1970s.31)

We disagree with the notion that the lead in white makeup powder significantly contributed to the high infant mortality rate during the Edo period. This is because children of high-ranking individuals, such as Shoguns and Daimyos, were not breastfed by their noble mothers, who typically used white makeup powder, but rather by nannies from middle- and lower-class warrior families (or sometimes townspeople).32-34) However, for adults, the possibility of lead poisoning as a cause of death cannot be entirely ruled out, particularly for high-ranking females of the Edo period. We believe that further investigation into this issue is necessary in the future.

Conclusion

In this study, we focused on the records of the Tokugawa Shogun family, for which the dates of birth and death are clearly and accurately documented. While records of other high-ranking families, such as the Daimyo or Hatamoto, are often biased, the well-managed records of the Shogun family throughout the Edo period are particularly valuable for estimating the LE of Edo-period Japanese. To eliminate biases caused by the lunar calendar and the traditional concept of age 0, we converted the date records to the solar calendar and counted the birth year as age 0. Our findings reveal that the LE of the Tokugawa family was much lower than that of modern Japanese, despite their status as the supreme elite class during the Edo period. This low LE is primarily attributed to the high infant mortality rate, while the mortality rate after age 10 remained relatively stable.