PCOS linked to higher risk of heart disease – even among women of normal weight

PCOS – one of the most common hormonal disorders among women of reproductive age – is often diagnosed in connection with irregular periods, increased hair growth or difficulty becoming pregnant. But the diagnosis transcends fertility.

New data now show that PCOS is also associated with a clearly elevated risk of blood clots and cardiovascular disease later in life – even among women of normal weight and without type 2 diabetes.

The data come from a joint Nordic study led in Denmark by Dorte Glintborg, consultant endocrinologist at Odense University Hospital and Clinical Professor at the University of Southern Denmark in Odense. Together with colleagues in Finland and Sweden, she followed women with PCOS and a large control group of women of the same age without the diagnosis.

The median age of the women was 28–29 years old at the start of the study, and they were followed for a median of 8–10 years. Over that time, the researchers recorded new cases of acute myocardial infarction, stroke, heart failure, pulmonary embolism, deep vein thrombosis in the legs and cardiovascular death – the major cardiovascular events.

Across all three countries, women with PCOS had roughly a 30% higher risk of cardiovascular disease than women without PCOS – meaning that for every 10 women without PCOS who experienced a cardiovascular event, about 13 women with PCOS did.

In the combined Nordic meta-analysis, the adjusted hazard ratio was 1.32. In other words, the risk was 32% higher even after the researchers accounted for differences in education, obesity and type 2 diabetes.

In Denmark, this corresponded to around 3 cases per 1,000 women per year versus just over 2 cases among women without PCOS – and the differences were similar in Finland and Sweden.

“The results suggest that prevention needs to become a routine part of follow-up for women with PCOS, regardless of their weight,” says Dorte Glintborg. “Blood pressure, cholesterol and blood sugar should be checked systematically among women with PCOS – including those of normal weight.”

A Nordic collaboration strengthens the evidence

The road to these results began in the outpatient clinic. For around 25 years, Dorte Glintborg has met women with PCOS presenting with everything from entirely new concerns to long and complex treatment journeys, in which the diagnosis has shaped daily life, fertility treatment and lifestyle. Over time, she became increasingly interested in what PCOS means for women’s long-term health – including the heart, once they reach the age at which cardiovascular disease becomes more common.

To obtain more robust answers, she joined forces with two research groups in Oulu, Finland and Uppsala, Sweden. Their initial plan was to conduct conventional clinical studies, closely monitoring smaller groups of patients. The ambition was to carry out identical studies in all three countries. But it proved difficult both to recruit enough participants in each location and to maintain a fully harmonised study design.

Instead, the researchers turned to the national health registries – databases in which all hospital diagnoses and treatments are recorded.

In Denmark, Finland and Sweden, individuals can be tracked across the healthcare system via personal identification numbers. The researchers identified all women with a PCOS diagnosis and matched them with age-matched controls without PCOS. Women with previous cardiovascular disease were excluded so that the analysis included only new events. Information on BMI was obtained from national birth registries.

Each national cohort was analysed separately and then combined in a meta-analysis – a method that pools results from several studies to provide a more reliable overall estimate. However, because of the registry-based design, detailed information on lifestyle factors such as smoking and alcohol use was not available, and body-mass index (BMI) data were only accessible for women who had been pregnant.

When the figures were compiled, they pointed in the same direction in all three countries: women with PCOS consistently had more blood clots and more cases of cardiovascular disease than women in the control group, and the differences between countries were small.

“The link between PCOS and cardiovascular disease appears to be consistent across the Nordic countries,” she emphasises.

Even women of normal weight are not exempt

Women with PCOS are more likely to have a higher BMI and to develop type 2 diabetes than women in the control group, and these classic risk factors account for part of the difference in heart disease.

But when the researchers statistically adjusted for education level, obesity and type 2 diabetes, the difference remained: women with PCOS continued to experience more cardiovascular disease than women without PCOS.

“Even when we take the other factors into account, PCOS still stands out as an independent risk factor,” says Dorte Glintborg.

Although PCOS is often associated with overweight, a substantial proportion of affected women who developed cardiovascular disease were of normal weight: 38% in Denmark, 49% in Finland and 42% in Sweden. In other words, more than one in three – and in Finland nearly one in two – were not overweight.

“Women of normal weight with PCOS do not always attract attention and can slip under the radar. But now that we are actively looking, they have more serious cardiovascular events than do normal-weight women without PCOS,” she says.

She also stresses that the absolute numbers of cardiovascular events remain relatively low among younger women – most occurred before the age of 50 years – but that even a moderate increase in risk becomes important when PCOS is so common and women are followed over decades.

When hormones put pressure on the blood vessels

The findings make the heart part of the PCOS story. The fact that women of normal weight also have increased risk suggests that the biology of the condition itself may affect the cardiovascular system – independently of weight and type 2 diabetes. In a separate analysis of women with a BMI below 25 and without type 2 diabetes, the adjusted risk remained 40% higher than in the control group.

One possible explanation lies in another hallmark of PCOS: elevated levels of male sex hormones.

These hormones can manifest as increased hair growth, acne and oily skin. In Nordic clinical studies, women of normal weight with PCOS have been found to have high blood pressure far more often than normal-weight women without PCOS. High blood pressure is a well-established independent risk factor for cardiovascular disease.

Taken together, the clinical findings and the new results suggest that hormonal influences in women with PCOS may contribute to the increased cardiovascular risk, partly through effects on blood pressure. Testosterone can cause blood vessels to constrict and become less flexible – a change that over time may strain the heart, explains Dorte Glintborg.

From one diagnosis to personalised risk profiles

The findings add a new layer to understanding PCOS as a chronic condition. Not all women with PCOS appear to face the same long-term risks, and those risks differ depending on whether the focus is diabetes, cardiovascular disease or mental health.

In the scientific article, the researchers note that weight plays a particularly important role in the risk of type 2 diabetes, whereas the analysis of cardiovascular disease in women of normal weight suggests that other mechanisms – such as elevated testosterone – may also be involved.

The observations regarding testosterone and blood pressure sharpen the biological picture: elevated male hormones not only cause visible symptoms such as hair growth and skin problems but also appear to affect the blood vessels and increase the strain on the heart.

For women living with PCOS, this means that the visible symptoms may be accompanied by a more hidden risk profile. Blood pressure can rise gradually without obvious symptoms, and the heart may be under strain even when weight remains within the normal range.

The research group is now working to divide PCOS into subgroups with different long-term risk patterns and is also investigating how mental health interacts with physical illness.

The ambition is for a diagnosis of PCOS to function more clearly as an early warning signal – and as an entry point to a comprehensive prevention strategy. Some women may benefit most from close monitoring of blood sugar and diabetes risk, others may benefit from a focus on blood pressure and cholesterol, and a third group may need targeted support for mental health.

“We are probably moving away from seeing PCOS as one single, uniform diagnosis. In the long term, we hope to be able to give each woman a more precise picture of her risk and a plan that extends beyond the next fertility treatment,” says Dorte Glintborg.

PCOS thus emerges not only as a fertility diagnosis but as an early signal of women’s long-term cardiovascular risk.