Practical Implications of the Update to the 2015 Japan Standard Population: Mortality Archive From 1950 to 2020 in Japan

Abstract

Background: The 2015 Japan Standard Population (JSP) was established in response to changes in the age structure. However, the effects of major updates, especially the recategorization of older age groups, for interpreting various health metrics have not been clarified.

Methods: Population data were collected and estimated for older age categories (85-89, 90-94, and ≥95 years). Data on the number of deaths were also collected from the Vital Statistics. We recalculated the all-cause and leading cause-specific age-standardized mortality rate (ASMR) using the 2015 JSP by the direct standardization method for data from 1950 to 2020. We compared ASMRs calculated using the 2015 JSP with those calculated using the 1985 JSP. Pearson's correlation coefficients were used to evaluate the consistency of mortality trends between the 2015 and 1985 JSPs.

Results: The absolute all-cause ASMRs calculated using the 2015 JSP were 2.22-3.00 times higher than those calculated using the 1985 JSP. The ASMR ratios increased gradually over time. While trends in all-cause and cause-specific ASMRs calculated using the 2015 JSP and 1985 JSP were generally highly correlated (Pearson's correlation coefficient [r] = 0.993 for all-cause), correlations were relatively low for malignant neoplasms (r = 0.720 for men and r = 0.581 for women) and pneumonia/bronchitis (r = 0.543 for men and r = 0.559 for women) due to non-monotonous trends over time and fluctuations in earlier time periods.

Conclusion: The effect of introducing the new JSP for interpreting trends in all-cause mortality was considered minimal. However, caution is needed when interpreting trends in some cause-specific mortality rates.

Keywords: age-standardized mortality; direct standardization method; standard population; the 1985 Japan Standard Population; the 2015 Japan Standard Population.

Figure 1.. Age distributions of standard populations. ^*Those 75 years and over are aggregated into one category in the Segi’s World Standard Population. ^**Those 85 years and over are aggregated into one category in the 1985 Japan Standard Population and the 2000 United States Standard Population

Figure 2.. Trends in the crude mortality rate across 5-year age categories (per 100,000 persons, log scale)

Figure 3.. Trends in the all-cause age-standardized mortality rate (ASMR) in Japanese men (A) and women (B) calculated using six different standard populations (per 100,000 persons)

Figure 4.. Correlation of all-cause age-standardized mortality rates (per 100,000 persons) calculated using the 1985 Japan Standard Population vs those calculated using the 2015 Japan Standard Population, 1950–2020. Pearson’s correlation coefficients: 0.993 (P < 0.01) for both sexes, 0.995 (P < 0.01) for men, 0.989 for women (P < 0.01)

Figure 5.. Trends in the cause-specific age-standardized mortality rate in men calculated using the 2015 Japanese Standard population, 1950–2020 (per 100,000 persons)

Figure 6.. Trends in the cause-specific age-standardized mortality rate in women calculated using the 2015 Japanese Standard population, 1950–2020 (per 100,000 persons)