Long-term trends in stroke and the impact of population aging in China: Results from the 2021 Global Burden of Disease Study

Based on the 2021 Global Burden of Disease Study, this paper reveals that while age-standardized rates for hemorrhagic strokes have declined in China since 1990, ischemic stroke incidence has risen and population aging has become a dominant driver of the overall stroke burden, necessitating targeted public health policies.

The Gist

Imagine China's population as a massive, bustling city. For decades, this city has been changing its demographic makeup: the number of young people moving in is slowing down, while the number of older residents is growing rapidly. This study acts like a long-term traffic report for one specific type of "accident" in this city: stroke.

The researchers looked at data from 1990 to 2021 to see how the "traffic" of three different types of strokes has changed. Think of these three types as different kinds of roadblocks:

1. Ischemic Stroke (IS): A blocked pipe (a clogged artery) stopping blood flow.
2. Intracerebral Hemorrhage (ICH): A burst pipe inside the brain.
3. Subarachnoid Hemorrhage (SAH): A burst pipe in the space surrounding the brain.

Here is what the "traffic report" revealed, broken down simply:

1. The "Blocked Pipe" Problem is Getting Worse

While the city's overall traffic rules have improved, the number of blocked pipes (Ischemic Stroke) is actually rising.

• The Trend: Even though the rate of these blockages per person has gone down slightly in some areas, the total number of cases has skyrocketed.
• The Analogy: Imagine a highway where the speed limit has been lowered (fewer accidents per car), but the number of cars on the road has tripled. The result? More total accidents, even if the road is "safer" per vehicle.
• The Cause: The study found that population aging is the main engine driving this rise. As the "city" gets older, more people are hitting the age where these blockages are likely to happen. In fact, if you look at the data from 1980 to 2021, the aging population alone is responsible for a massive chunk of the increase in deaths from this type of stroke.

2. The "Burst Pipe" Problems are Getting Better

The other two types of strokes—burst pipes inside the brain (ICH) and burst pipes around the brain (SAH)—are showing a different story.

• The Trend: Both the number of cases and the death rates for these types have dropped significantly over the last 30 years.
• The Analogy: It's like the city finally fixed its old, brittle water mains. Even though the city is bigger, fewer pipes are bursting.
• The Success: The study suggests that China's control over these specific types of strokes is actually better than in many other parts of the world, including some wealthier regions. This is likely due to better medical care, awareness campaigns (like "World Stroke Day"), and improved emergency services.

3. The "Aging" Factor is the Heavy Lifter

The study used a special math tool (called "decomposition analysis") to figure out why the numbers changed. They broke the change down into three ingredients:

1. Population Size: More people overall.
2. Population Aging: People getting older.
3. Age-Specific Rates: How risky the disease is for a person of a specific age.

The Big Reveal:
For Ischemic Stroke, the "Aging" ingredient is the heavyweight champion.

• The study found that for men, the aging population contributed to 279% of the increase in deaths (meaning the rise in deaths was almost entirely because the population got older, overwhelming any medical improvements).
• For women, it was 204%.
• Essentially, medical advances are trying to push the numbers down, but the sheer weight of an aging population is pushing them up even harder.

4. Men vs. Women

The "traffic" isn't the same for everyone.

• Men: They are driving faster into the danger zone. The rise in blocked pipes (Ischemic Stroke) is steeper for men, and their death rates are higher.
• Women: They are doing slightly better. While they are also seeing more cases due to aging, the decline in the "burst pipe" types (ICH and SAH) is happening faster for women than for men.

The Bottom Line

The paper concludes that while China has done a fantastic job fixing the "burst pipes" (hemorrhagic strokes), the "blocked pipes" (ischemic strokes) are becoming a bigger problem simply because the population is getting older.

The "city" is aging so fast that it is creating a new wave of health challenges. The study suggests that to handle this, the focus needs to shift toward early screening and prevention specifically for the elderly, acknowledging that the rising tide of aging is the primary force driving these numbers up.

Note: This paper is a preprint, meaning it hasn't been through the final "peer review" checklist yet, but it offers a clear snapshot of these long-term trends based on global health data.

Technical Summary

Technical Summary: Long-term trends in stroke and the impact of population aging in China (1990–2021)

Problem Statement
Stroke remains a primary cause of morbidity, mortality, and disability in China, accounting for approximately one-third of global stroke deaths. While the epidemiological landscape of stroke in China has shifted significantly over recent decades, there is a lack of systematic analysis regarding stroke subtypes (Ischemic Stroke [IS], Intracerebral Hemorrhage [ICH], and Subarachnoid Hemorrhage [SAH]) in the context of China's rapidly aging population. The authors identify a critical gap in understanding how population aging specifically influences the long-term burden of stroke subtypes, which limits the ability of policymakers to reform healthcare systems and address the specific needs of the elderly.

Methodology
This study utilizes data from the Global Burden of Disease (GBD) Study 2021, covering 204 countries and territories. The analysis focuses on China from 1990 to 2021 for incidence and disability-adjusted life years (DALYs), and from 1980 to 2021 for mortality.

• Data Sources: Original data were derived from nationally representative sources, including the Cause of Death Reporting System of the Chinese Center for Disease Control and Prevention, Disease Surveillance Points, and the Maternal and Child Surveillance System.
• Statistical Measures: The study calculated age-standardized incidence rates (ASIR), age-standardized mortality rates (ASMR), and age-standardized DALY rates (ASDR) for IS, ICH, and SAH, stratified by sex and age groups (5-year intervals).
• Trend Analysis: The Estimated Annual Percentage Change (EAPC) was calculated using log-linear regression to assess long-term trends. Joinpoint regression analysis was employed to identify significant trend change points.
• Decomposition Analysis: A decomposition method was applied to attribute changes in incidence, death, and DALYs between two time points to three independent factors: (a) population size, (b) population aging, and (c) age-specific rates. This allowed for the quantification of the specific contribution of aging to the stroke burden.
• Tools: Statistical analyses were conducted using R 4.3.1 and the Joinpoint Regression Program (version 5.1.0).

Key Results

• Divergent Trends by Subtype: From 1990 to 2021, the age-standardized incidence rate (ASIR) of Ischemic Stroke (IS) increased significantly, rising from 100.05 to 135.79 per 100,000 (EAPC: 0.94). Conversely, the ASIRs for ICH and SAH declined, with EAPCs of –2.24 and –3.70, respectively.
• Mortality and Disability: While the absolute number of stroke cases and deaths increased, the age-standardized mortality rate (ASMR) and ASDR for overall stroke peaked around 2004 and have since shown a downward trend. However, the ASMR for IS in men showed a slight increasing trend (EAPC: 0.20), whereas it decreased for women.
• Impact of Population Aging: Population aging was a major driver of the increased stroke burden. Between 1980 and 2021, the number of people aged 60 and above in China increased by 169%. The decomposition analysis revealed that population aging contributed to a massive increase in IS-related deaths. In 2021, the proportion of IS deaths attributable to aging was calculated at 279.4% for men and 204.8% for women, indicating that the burden imposed by aging far exceeded the total burden in the reference year (1990/1980).
• Demographic Disparities: Men generally exhibited higher incidence, mortality, and DALY rates than women. The incidence of IS increased notably in men over 10 years old, with the most pronounced trend in the 75–79 age group. Women showed a more consistent downward trend across most metrics compared to men.
• International Context: Compared to other Socio-demographic Index (SDI) regions, China's control of ICH and SAH was superior, exceeding trends in other regions. However, the control of IS in China was less effective than in other SDI regions, showing a linear upward trend in incidence.

Significance and Claims
The authors claim that this study provides a scientific basis for addressing disease management challenges posed by an aging population in China. The primary significance lies in the quantification of the "dual pattern" of increasing aging and declining birth rates driving the stroke burden.

• Policy Implications: The study highlights that while medical advancements and public health initiatives (such as the World Stroke Day campaign in 2004) have successfully reduced age-standardized rates for hemorrhagic strokes, these gains are being offset by the sheer demographic shift toward an older population, particularly for Ischemic Stroke.
• Targeted Interventions: The authors argue that the rising burden of IS, especially among the elderly and increasingly among younger demographics due to risk factors like obesity, necessitates targeted policies. They call for improved early screening, intervention measures, and the adoption of new technologies to enhance the quality of life for the aging population.
• Limitations: The authors modestly acknowledge limitations, including the reliance on modeled data (DisMod-MR), the lack of provincial-level analysis, the absence of specific risk factor analysis, and the decomposition method's exclusion of factors other than population size, aging, and age-specific rates.

In conclusion, the paper asserts that while China has made significant progress in managing hemorrhagic strokes, the management of Ischemic Stroke remains insufficient. The aging population is responsible for more than half of the increase in the stroke burden, requiring urgent policy attention to support early detection and treatment for the elderly.