Charting the Decline of the Fourth Wave: US Overdose Deaths by Race, Ethnicity, and Substance Involvement

Between 2023 and 2024, the United States experienced a significant 24.4% decline in overdose death rates driven by a sharp drop in fentanyl-involved deaths, marking the first decrease in the "fourth wave" of the crisis, though substantial racial disparities persist with American Indian/Alaska Native and Black individuals continuing to face the highest mortality rates.

The Gist

Imagine the United States' drug overdose crisis as a massive, relentless storm that has been battering the country for decades. For years, this storm only got stronger, with waves crashing harder and harder against the shore. But according to this new research, something remarkable has happened: the storm is finally starting to break.

Here is the story of that shift, told in simple terms with a few metaphors to help visualize what's going on.

The Four Waves of the Storm

Scientists have been tracking this crisis by dividing it into "waves," like the tides of an ocean. Each wave brought a different type of danger:

1. Wave 1 (The Prescription Surge): In the late 90s and early 2000s, the storm was driven by too many painkiller prescriptions.
2. Wave 2 (The Heroin Swell): As prescriptions got tighter, the tide shifted to heroin.
3. Wave 3 (The Fentanyl Tsunami): Then came the most deadly wave yet: illicit fentanyl, a synthetic opioid so powerful it's like a chemical tsunami.
4. Wave 4 (The Toxic Mix): The most recent wave wasn't just fentanyl; it was fentanyl mixed with stimulants like meth and cocaine. It was a "toxic cocktail" that made the storm even more unpredictable and deadly.

The Big News: For the first time in history, all four of these waves are receding at the same time. The water is going down. Between 2023 and 2024, the total number of overdose deaths dropped by nearly 25%. That is a massive, historic drop.

Why Did the Water Recede?

The authors suggest a few reasons why the storm is calming down, though they aren't 100% sure yet:

• The "Fentanyl Drought": Imagine a factory that makes the poison suddenly running out of ingredients. There might have been a disruption in the supply chain (perhaps from China), making high-purity fentanyl harder to get.
• The "Survivor Effect": Tragically, the population of people at highest risk has shrunk because so many have already passed away, and fewer new people are starting to use these specific drugs.
• Better Safety Nets: More people are carrying naloxone (Narcan), the "fire extinguisher" that puts out an overdose, and more people are switching from injecting drugs to smoking them, which is slightly less risky.

The "New" Danger: The Rising Tide of Stimulants

While the main storm (fentanyl) is shrinking, a different kind of weather is brewing.

Think of the crisis like a house fire. The main fire (fentanyl) is being put out, but while the firefighters are busy, a new fire is starting in the kitchen.

• Deaths involving stimulants alone (meth and cocaine without fentanyl) are actually increasing.
• Deaths involving xylazine (a veterinary sedative often mixed with fentanyl) are also rising.

Even though the total number of deaths is down, these new dangers are taking up a bigger slice of the pie. If the fentanyl tide keeps going down but the stimulant tide keeps rising, stimulants could soon become the biggest threat on their own.

The Uneven Shore: Who is Still in Danger?

The storm didn't hit everyone equally, and even as the water recedes, some neighborhoods are still underwater while others are just getting their feet wet.

• The Good News: The group that suffered the most in recent years—Black and African American communities—saw the biggest drop in deaths (nearly 30%). This is a huge victory and means the gap between different groups is starting to close slightly.
• The Bad News: The gap is still very wide.
  • American Indian and Alaska Native communities still have the highest death rates in the country (more than double the national average).
  • Black and African American communities still die at rates 50% higher than the national average.

It's like the water level dropped for everyone, but the people living on the highest hills (White communities) are now dry, while the people living in the deep valleys (Black and Native communities) are still wading through chest-deep water.

The Bottom Line

The United States is experiencing a "historic moment." The worst part of the overdose crisis seems to be turning a corner. The "Fourth Wave" is crashing down for the first time.

However, we can't just celebrate and go home. The storm isn't over; it's just changing shape. We need to keep fighting the fentanyl battle while also building better defenses against the rising tide of stimulants and xylazine. And most importantly, we need to make sure the "lifeboats" (treatment and safety measures) reach the communities that are still drowning, so that when the water finally recedes, everyone is safe on dry land.

Technical Summary

1. Problem Statement

The United States has experienced a prolonged and escalating drug overdose crisis, historically characterized by a "four-wave" paradigm:

1. Wave 1: Surge in prescription opioid deaths.
2. Wave 2: Rapid increase in heroin-related deaths.
3. Wave 3: Market dominance of illicitly manufactured synthetic opioids (primarily fentanyl).
4. Wave 4: Polysubstance deaths involving fentanyl combined with illicit stimulants (cocaine and methamphetamine) and the veterinary sedative xylazine.

While recent data suggested a potential turning point in 2023, there was a lack of comprehensive, granular analysis regarding the trajectory of these specific waves through 2024, particularly concerning racial and ethnic disparities. The study addresses the need to characterize whether the overall decline in overdose deaths is uniform across substance types and demographic groups, or if specific sub-trends (e.g., stimulant-only deaths) are diverging.

2. Methodology

• Study Design: A population-based, retrospective analysis of national death records.
• Data Source: CDC Wide-ranging ONline Data for Epidemiologic Research (WONDER) platform.
• Time Period: January 1, 1999 – December 31, 2024.
• Case Definition: All individuals who died from drug overdose, defined by ICD-10 underlying causes of death (UCD) codes:
  • Unintentional: X40–X44
  • Suicide: X60–X64
  • Homicide: X85
  • Undetermined intent: Y10–Y14
• Substance Classification: Secondary characterization using ICD-10 multiple cause of death codes:
  • Prescription opioids (T40.2)
  • Heroin (T40.1)
  • Synthetic opioids/Fentanyl (T40.4)
  • Cocaine (T40.5)
  • Psychostimulants/Methamphetamine (T43.6)
  • Xylazine (T42.7 or T46.5)
• Analytical Approach:
  • Fentanyl-Deleted Rates: To isolate trends for specific substances, the authors calculated "fentanyl-deleted" death rates by subtracting deaths involving the substance plus fentanyl from the total deaths involving that substance.
  • Demographic Stratification: Data were stratified by race/ethnicity (Non-Hispanic White, Black/African American, American Indian/Alaska Native, etc.).
  • Statistical Tools: Analyses were conducted in R version 4.4.1. Rates were calculated as crude deaths per 100,000 population.
• Data Limitations: 2024 data are provisional and may slightly underestimate final counts. Multiracial individuals were excluded from counts starting in 2018 due to changes in classification standards.

3. Key Contributions

• Confirmation of the Fourth Wave's Decline: This is the first study to document that the "fourth wave" (fentanyl + stimulants) has begun to decline in magnitude, marking a simultaneous decrease across all four defined waves of the crisis.
• Granular Disparity Analysis: Provides the most recent breakdown of overdose mortality by race/ethnicity and specific substance combinations, highlighting that while disparities are narrowing, they remain profound.
• Identification of Diverging Trends: Distinguishes between the declining fentanyl crisis and the increasing burden of stimulant-only deaths and xylazine involvement, suggesting a shift in the future public health challenge.
• Epidemiological Context: Offers a critical update on the "fentanyl drought" hypothesis and the role of premature mortality in reducing the at-risk population.

4. Key Results

• Overall Decline: The US overdose death rate dropped 24.4% between 2023 and 2024, falling to 23.7 per 100,000.
• Wave Trajectories:
  • Wave 3 (Fentanyl only): Decline began in 2022.
  • Wave 4 (Fentanyl + Stimulants): Decline began in 2024 for the first time.
  • Stimulants (No Fentanyl): Deaths continued to rise, increasing from 18,142 (2023) to 18,907 (2024). These now represent 23.8% of all overdose deaths.
  • Xylazine: While absolute numbers held steady, its proportion of fentanyl-involved deaths rose from 8.3% (2023) to 12.6% (2024).
• Substance Volume Changes (2023 vs. 2024):
  • Fentanyl without stimulants: 31,193 $\rightarrow$ 19,673.
  • Fentanyl with stimulants: 41,583 $\rightarrow$ 28,062.
• Racial/Ethnic Disparities:
  • Black/African American: Experienced the largest relative decrease (29.3%), falling to 36.0 per 100,000. However, this rate remains 1.51 times the national average. Cocaine-involved deaths (fentanyl-deleted) are 3.13 times the national average for this group.
  • American Indian/Alaska Native (AI/AN): Had the highest absolute rate in 2024 (50.8 per 100,000), which is 2.15 times the national average. They experienced a below-average relative decrease (20.1%). Methamphetamine-involved deaths (fentanyl-deleted) for this group are 3.24 times the national average.
  • Non-Hispanic White: Rates were near the national average (24.8 per 100,000) with a 23.9% decrease.

5. Significance and Implications

• Historic Turning Point: The simultaneous decline of all four waves represents a "historic moment" in the US overdose crisis, likely driven by a combination of a "fentanyl drought" (supply disruption), increased population awareness of fentanyl risks, and a reduction in the at-risk population due to premature mortality.
• Shifting Public Health Challenge: As fentanyl deaths decline, stimulants without fentanyl are becoming the defining addiction-related challenge. The authors argue that focusing solely on overdose deaths may be insufficient, as stimulant use drives significant morbidity (cardiovascular, psychiatric, and neurovascular issues) that is not captured by mortality data alone.
• Persistent Inequities: While racial disparities narrowed slightly in 2024, the absolute gaps remain severe. The AI/AN and Black populations continue to suffer disproportionately, particularly regarding methamphetamine and cocaine.
• Policy Recommendations:
  • Sustained investment in evidence-based treatments (Medications for Opioid Use Disorder, harm reduction).
  • Targeted interventions for the most affected racial/ethnic groups.
  • Expansion of surveillance beyond overdose mortality to include morbidity metrics (e.g., DALYs) to fully capture the burden of stimulant use disorders.

Conclusion: The US is witnessing a significant, albeit fragile, reversal in overdose mortality driven by a sharp drop in fentanyl-related deaths. However, the crisis is evolving rather than resolving, with rising stimulant and xylazine burdens and persistent racial inequities requiring continued and tailored public health interventions.