Breast cancer rates have risen rapidly among Asian American women over the past two decades, with some of the steepest increases among women under 50, new research has revealed.

Rates rose by more than three per cent a year in nearly every Asian American ethnic group studied, much faster than in any other US ethnic group.

The increase was particularly marked among women under 50 and in cases involving advanced-stage disease or certain aggressive subtypes of the cancer.

The study found even larger increases among Chinese and Vietnamese women.

Breast cancer rates among Native Hawaiian women were already among the highest recorded among US women, but rose by about one per cent a year, less than the increases seen in Asian American groups.

The researchers said increased screening was unlikely to explain the trend because screening would be expected to identify more cancers at an earlier stage.

Instead, cancers that had already spread increased at the fastest rate.

Triple-negative breast cancer, considered the most aggressive subtype, rose by more than six per cent a year among Chinese American women between 2017 and 2022.

Scarlett Lin Gomez, senior author and professor of epidemiology and biostatistics at the University of California, San Francisco, said: “These patterns are highly concerning from a disparities standpoint.

“They underscore why it is so important to move beyond treating Asian Americans, Native Hawaiians, and Pacific Islanders as a single population.”

Researchers analysed about 150,000 cases of invasive breast cancer diagnosed between 2000 and 2022 using data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Programme.

The analysis covered nine Asian American, Native Hawaiian and Pacific Islander populations across 14 states. Together, these states account for about two-thirds of the US population within these groups.

Except for Native Hawaiian women, Asian American women have historically had lower breast cancer rates than non-Hispanic white women.

However, the gap has narrowed rapidly. By 2022, incidence among Asian American women under 50 was comparable with that recorded among white women.

The reasons for the increase among women under 50 remain unclear.

Changes in reproductive patterns, diet and other lifestyle factors may play a part, but researchers said they did not fully explain the findings.

They said previously unidentified risk factors may also be contributing to the rises in some Asian American communities.

Researchers hope two UCSF-based studies, the CRANE breast cancer study and the ASPIRE cohort study, will provide insights into these factors.

Gomez said: “Understanding why breast cancer is increasing so rapidly in these communities is critical.

“At the same time, we need to ensure that women across all Asian American, Native Hawaiian, and Pacific Islander communities have access to culturally appropriate education, screening, and timely follow-up care.”

Softening ageing ovaries could help women remain fertile for longer, early animal research suggests.

Fertility declines with age for several reasons, including poorer egg quality, fewer ovarian follicles and the gradual stiffening of ovarian tissue.

Existing fertility treatments, including hormone therapy and in vitro fertilisation, mainly address hormonal imbalances or help eggs mature or become fertilised.

Scientists are now examining whether changing the physical structure of the ovaries could provide another route for future fertility treatments.

Stuart A. Cook, of the Cardiovascular and Metabolic Disorders Programme at Duke-National University of Singapore Medical School, published an accompanying commentary on the research.

Researchers led by Shixuan Wang at Huazhong University of Science and Technology in Wuhan, China, collected healthy ovarian tissue from younger, middle-aged and older women.

They also examined samples from patients with polycystic ovary syndrome, known as PCOS, premature ovarian insufficiency, or POI, and endometriosis.

PCOS is a hormonal condition that can disrupt ovulation. POI occurs when the ovaries stop working normally before the age of 40, while endometriosis causes tissue similar to the womb lining to grow elsewhere in the body.

Tests of protein levels and gene activity found higher levels of the inflammatory protein interleukin-11, or IL-11, in ageing and diseased ovaries.

In laboratory experiments, the researchers exposed ovarian fibroblasts to IL-11. Fibroblasts are cells that produce connective tissue.

The protein caused the cells to produce excess collagen, a structural material that can build up during scarring and make tissue stiffer.

The researchers then genetically modified mice so they could not respond to IL-11. The animals developed less ovarian stiffening and maintained better ovarian function as they aged.

Similar results were seen in mouse models of PCOS and POI caused by chemotherapy.

In the final part of the experiment, older mice and rats were injected with a nanoparticle treatment containing small interfering RNA, or siRNA, designed to switch off IL-11.

The treatment made the animals’ ovaries less stiff and improved fertility.

Pregnancy rates among older mice rose from 25 per cent to 50 per cent, while average litter sizes also increased.

More rats treated with the therapy became pregnant and produced larger litters.

The approach remains highly speculative and will require considerably more research before its safety or effectiveness in women can be established.

However, the researchers said blocking the inflammatory pathway could eventually form the basis of new fertility treatments.

They said: “We propose that anti-IL-11 therapy represents a promising translational strategy for delaying ovarian ageing.”

SSRIs may help women with depression tolerate extreme heat, with responses more like those without depression, a laboratory study suggests.

Selective serotonin reuptake inhibitors, or SSRIs, are medicines commonly used to treat mental health conditions including depression and anxiety.

Media reports, social media posts and the US Centers for Disease Control and Prevention have suggested SSRIs may increase vulnerability to heat-related illness.

However, researchers found that women with clinical depression who took an SSRI may withstand extreme heat better than those not treating their depression with medication.

The study was carried out by researchers in the Penn State Department of Kinesiology.

Kathleen Fisher, first author of the study, said: “The human body primarily cools itself in two ways, by sweating and by increasing blood flow to the skin so that heat can be released to the environment.

“This study showed that depression interferes with how women’s bodies regulate their temperatures in the heat. Fortunately, SSRIs seem to largely restore the body’s ability to respond to increases in internal temperature.”

The team compared women without depression with those diagnosed with the condition, including women taking different types of antidepressants.

When their body temperatures rose, women with untreated depression were slower to begin sweating and increasing blood flow to the skin.

Their bodies were also less efficient at pumping blood to the skin than those of women without depression and women taking an SSRI.

Depression affects about 10 per cent of the US population and is twice as common among women, the researchers said.

SSRIs, including sertraline and fluoxetine, and serotonin and noradrenaline reuptake inhibitors, or SNRIs, including duloxetine and venlafaxine, are commonly prescribed alongside counselling to treat depression.

Previous research suggests depression disrupts the body’s ability to regulate temperature.

Penn State researchers had previously found that blood vessels dilated less effectively in women with depression. Dilation allows blood vessels to widen, helping more blood reach the skin to cool the body.

Women taking SSRIs showed improved blood vessel dilation similar to that seen among people without depression.

The latest study examined whether the same improvement occurred during heat stress.

Researchers recruited 64 women, almost all in their 20s. The group included 16 without depression and 16 with depression who were not taking medication.

A further 16 had depression and were taking an SSRI, while 16 had depression and were taking an SNRI.

Participants swallowed a small capsule that transmitted their internal body temperature throughout the experiment.

They then wore a suit fitted with tubes that allowed researchers to pump heated water through it.

After 10 minutes of adjusting to water at 91°F, around 33°C, the temperature was raised to 125°F, around 52°C.

The experiment ended when each participant’s internal temperature had risen by 1.8°F, or 1°C. This took an average of 45 minutes.

Researchers also measured skin temperature on the arm, calf, chest and thigh, along with heart rate, blood pressure, blood flow to the skin and sweating.

Professor W Larry Kenney, a study co-author, said: “The water pumped into the suit was 125 F, causing skin temperature to rise to about 100 F.

“As the skin continued to be heated to temperatures similar to sitting in a hot tub, the women’s internal temperature continued to rise.”

Women with untreated depression were slower to begin sweating and increasing blood flow to the skin than women without depression.

When blood flow to the skin increased, it was less efficient. Despite beginning to sweat later, women with untreated depression did not sweat less overall.

Women taking SSRIs responded to heat in a similar way to women without depression.

By contrast, women taking SNRIs responded similarly to those with untreated depression. SSRIs therefore normalised responses to heat stress, while SNRIs did not.

Researchers found no differences in blood pressure between the four groups.

Fisher said: “Up until now, there has been very little data on how depression or any of these classes of antidepressive drugs affect people’s responses to heat stress.

“This study took the first step toward understanding how women with depression, whether taking medications or not, may respond to extreme heat.”

Kenney said the findings challenged common beliefs that SSRIs increase vulnerability to heat.

He said: “In prior studies, my collaborators and I have identified how several factors, especially age, sex, and activity level, contribute to risk from extreme heat.

“Additionally, there has been widespread concern that many medications contribute to heat vulnerability, but the research evidence behind the risks of many medicines is often thin or nonexistent.

“Both physicians and people taking SSRIs should be aware that these medications do not seem to contribute to heat vulnerability. Rather, SSRIs improve heat tolerance in depression.”