A new study has found that, amid record low infant mortality rates in 2020, rates of sudden infant death syndrome, known as SIDS, increased for the first time in five years, and there was a sharp increase in the rate of sudden unexpected infant deaths, or SUID, among Black infants between 2019 and 2020.

The study, published by the American Academy of Pediatrics with research from the Centers for Disease Control and Prevention, found that the SUID rate per 100,000 live births was highest among Black infants in 2020, surpassing the SUID rate among non-Hispanic American Indian or Alaskan Native infants, which had been declining since 2015.

Black babies recorded 214 deaths per 100,000 while American Indian or Alaskan Native infants recorded 205.1 deaths per 100,000, nearly three times the rate of non-Hispanic white infants, which were recorded at 75.6 deaths per 100,000, according to the research.

The lowest SUID rates were observed among Hispanic and Non-Hispanic Asian infants with 59 deaths per 100,000 and 23.3 deaths per 100,000.

"There's been a long-standing disparity in sudden unexpected infant death with non-Hispanic Black Americans having more than twice the rate of the general population, and then an even higher increase in the rate compared to non-Hispanic white (babies)," Rebecca Carlin, M.D., who co-authored the commentary released with the study, told ABC News. "In a lot of ways, the pandemic only increased a lot of the causes of that disparity."

When asked if the results of the study were surprising, Carlin told ABC News that she doesn't think so.

"I think that these authorities have been so long-standing and they've been so difficult to address that any event that increases disparities generally, it's not surprising that it would also increase disparities in SUID deaths," she added.

"Sudden unexplained infant deaths" includes deaths categorized as "sudden infant death syndrome," "accidental suffocation and strangulation in bed," and "unknown cause."

PHOTO: A babies feet are seen in this undated stock photo.
STOCK PHOTO/Getty Images
A babies feet are seen in this undated stock photo.

"Sudden infant death syndrome" is a term coined to define sudden and unexpected deaths of infants less than 1 year old due to an unknown cause, or a cause not obvious before their death, as defined by the CDC.

This study included SUID rates and its sub-categorizations, including SIDS.

In the commentary released with the study, the authors discuss that the results of the study highlighting the SUID disparities between races reflected a current societal phenomenon.

"This rise further increases the already existing disparities in these deaths, with the rate among infants born to non-Hispanic Black families now 2.3-fold higher than the general population and 2.8-fold higher than infants born to non-Hispanic white families," the study's commentary authors wrote.

Researchers found the disparities while studying the increase in SIDS from 2015-2020. After four years of a steady decline in SIDS from 2015 to 2019, they saw a 15% rise during the first pandemic year, from 33.3 deaths per 100,000 in 2019 to 38.2 per 100,000 in 2020.

While there is no known cause for the spikes in SUID and SIDS cases from 2019-2020 for non-Hispanic Black infants, the commentary speculated on factors that may have contributed to the increase.

"These disparities are likely multifactorial, reflecting poverty levels, lack of access to prenatal and well-child care, and education regarding safe sleep and other practices, including the feeding of human milk, which can reduce the risk of SUID, and social norms related to these practices that vary between communities," the commentary read.

The authors also noted the increase in SIDS in 2020 may be due to how the deaths are being diagnosed.

Carrie Shapiro-Mendoza, Ph.D., one of the researchers of the study, agreed with those disparities and voiced what she thinks are contributing factors to the spike in a statement sent to ABC News.

"We know that the COVID-19 pandemic and related mitigation efforts (e.g., stay-at-home orders) disproportionately affected racial and ethnic minority communities compared to non-Hispanic white communities. It may have led to more unsafe sleep practices like bedsharing, thereby increasing the occurrence of SIDS and other sudden unexpected infant deaths," said Shapiro-Mendoza, who holds a master's degree in public health.

"More research is needed to address persistent racial or ethnic disparities in SUID," she added. "By better understanding the factors that influence the trends in these rates and finding new approaches to encourage safe sleep practices, we can help reduce future infant deaths."