From 1990 to 2019, global death rates from influenza declined significantly overall but rose in older adults and those living in certain regions, Zhejiang University researchers in China reported this week in Epidemiology & Infection.
The study evaluated global trends in deaths from flu-related lower respiratory infections (LRIs) from 1990 to 2019 using data from the 2019 Global Burden of Disease study. The investigators analyzed data on annual percentage change (APC) and average annual percentage change (AAPC) to assess age-standardized death rates (ASDRs).
"In 2019, lower respiratory infections (LRIs) accounted for approximately 2.6 million global fatalities, which ranked as the fourth leading cause of death and the second leading cause of disability-adjusted life-years," the study authors noted.
Western Pacific region especially hard-hit
Globally, the ASDR of flu-related LRIs was 3.29 per 100,000 people in 2019 but was higher in the African region (6.57/100,000), among adults aged 70 years and older (29.88/100,000), and in males (4.00/100,000 vs 2.78/100,000 in females). The sex difference can be attributed to a higher rate of common infectious diseases among males, potential variations in immune responses, and behaviors such as smoking and alcohol use, the authors said.
The ASDR of flu-related LRIs fell significantly from 1990 to 2019 (AAPC, -1.88%) but was notably higher among adults aged 70 years and older from 2017 to 2019 (AAPC, 2.31%) and in the Western Pacific region (AAPC, 6.48%).
Death rates of children aged 5 years and younger (11.06/100,000) and adults aged 70 years and older (50.61/100,000) were both highest in the African Region.
The Americas (34.39/100,000) and Western Pacific (33.71/100,000) regions also had a higher death rate among adults aged 70 years and older. The death rate among children aged 5 years and younger showed a significant decrease (-4.49%), but in many countries and territories, the rate in older adults remained stable or demonstrated an increasing trend.
The death-rate ratio of adults aged 70 years and older and children younger than 5 years climbed globally, from 1.63 in 1990 to 5.34 in 2019, with the Western Pacific Region experiencing the largest increase (1.83 in 1990 to 12.98 in 2019).
National flu surveillance systems key
The age-related differences in death rates may be due to a higher prevalence of malnutrition, chronic diseases, reduced antibody levels, and inflammatory responses in older adults. "This emphasizes the importance of implementing timely prevention and intervention measures specifically targeting these high-risk groups," the investigators wrote.
Government and health organizations can formulate and implement public health policies for the elderly, including vaccination promotion and disease surveillance.
The regional increases in deaths among older adults could have been influenced by low vaccine uptake in this age-group, possibly due to vaccine hesitancy, weak healthcare infrastructure, limited access to vaccination services, or suboptimal vaccine efficacy in the hardest-hit areas.
"Government and health organizations can formulate and implement public health policies for the elderly, including vaccination promotion and disease surveillance," the researchers wrote. "It is crucial to establish an effective national influenza surveillance system to deliver timely and comprehensive estimates of the burden on high-risk populations, seasonality, circulating strains and subtypes, and the cost-effectiveness of national influenza vaccination."
