Three decades of population health changes in Japan, 1990–2021: a subnational analysis for the Global Burden of Disease Study 2021

Background: Given Japan's rapidly ageing demographic structure, comprehensive and long-term evaluations of its national and subnational health progress are important to inform public health policy. This study aims to assess Japan's population health, using the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 to analyse the country's evolving disease patterns. 

Methods: GBD 2021 used Japanese data from 1474 sources, covering 371 diseases, including COVID-19, and 88 risk factors. The analysis included estimates of life expectancy, mortality, and disability-adjusted life-years (DALYs). Estimates were generated using the standardised GBD methodology, which incorporates various data sources through statistical modelling, including the Cause Of Death Ensemble Model for mortality, Bayesian Meta-Regression Disease Model for non-fatal outcomes, and risk factor estimation frameworks to quantify attributable burdens. Life expectancy decomposition by cause of death and annualised rates of change of age-standardised mortality and DALYs were calculated for 1990–2005, 2005–15, and 2015–21. 

Findings: Between 1990 and 2021, life expectancy in Japan rose from 79·4 years (95% uncertainty interval 79·3–79·4) to 85·2 years (85·1–85·2), with prefecture-level disparities widening. Gains were primarily driven by reduced mortality from stroke (adding 1·5 years to life expectancy), ischaemic heart disease (1·0 years), and neoplasms, particularly stomach cancer (0·5 years), with variation across prefectures. Leading causes of death in 2021 were Alzheimer's disease and other dementias (135·3 deaths [39·5–312·3] per 100 000 population), stroke (114·9 [89·8–129·3] per 100 000), ischaemic heart disease (96·5 [77·7–106·7] per 100 000), and lung cancer (72·1 [61·8–77·5] per 100 000). Age-standardised mortality for major non-communicable diseases declined, but the pace of this decline has slowed. All-cause annualised rate of change in mortality rate decreased from –1·6% for 2005–15 to –1·1% for 2015–21. Age-standardised COVID-19 mortality rates were 0·8 deaths (0·7–0·9) per 100 000 population (accounting for 0·3% of all deaths) in 2020 and 3·0 (2·5–3·7) per 100 000 population in 2021 (1·0% of deaths). Age-standardised DALY rates for diabetes worsened, with annualised rate of change increasing from 0·1% for 2005–15 to 2·2% for 2015–21. This change parallels worsening trends in major risk factors, particularly high fasting plasma glucose (annualised rate of change of attributable DALYs –0·8% for 2005–15 and 0·8% for 2015–21) and high BMI (0·2% and 1·4%, respectively). Age-standardised DALYs attributable to other major risk factors continued to decrease, albeit slower. 

Interpretation: Japan's health gains over the past 30 years are now stalling, with rising regional disparities. The increasing burdens of Alzheimer's disease and other dementias and diabetes, alongside high fasting plasma glucose and high BMI, highlight areas needing focused attention and action. 

Funding: Gates Foundation.