Higher body mass index (BMI) predicted MI and ischemic stroke in younger women within four to five years of giving birth, according to nationwide study of Danish women to be presented at the American College of Cardiology (ACC) scientific sessions in San Francisco.

Researchers at the University of Copenhagen, in an ACC statement, said that while these events are very rare among women of this age, their findings indicate “a very clear and strong link between carrying excess weight and suffering a heart attack or stroke.”

Using data from nationwide registries, as well as the Danish Medical Birth Register, which collects women’s height and weight, the study’s lead investigator, Michelle Schmiegelow, a PhD student, and her colleagues at the University of Copenhagen identified 273,101 women at average age of 30.5 years who had no history of acute coronary syndrome, stroke or renal insufficiency, who had given birth in 2004 through 2009.

Every Danish citizen has a unique and permanent identification number which follows him or her from birth to death. It enables cross-linkages of all registries in Denmark, allowing researchers to conduct nationwide studies of rare events.

During a median follow-up period of 4.3 years, 68 women experienced an MI, while 174 women experienced an ischemic stroke.

Researchers grouped the women into four BMI groups: underweight (BMI <18.5 kg/m2), normal weight (BMI 18.5-24.9 kg/m2), overweight (BMI 25-29.9) and obese (BMI > 30). The unadjusted hazard ratios of MI were 2.61 in underweight women, 1.82 in overweight women and 3.35 in obese women. With regard to ischemic stroke, unadjusted hazard ratios were 1.13, 1.36 and 2.07 in underweight, overweight and obese women, respectively. These associations remained unchanged even after accounting for other pregnancy-associated complications or cardiovascular risk factors, including smoking.

“Young women need to be aware that there are serious health risks associated with obesity and poor lifestyle habits, and these [negative effects] appear to set in early,” said Schmiegelow said in the statement. “This study is important because although the incidence of heart disease is declining overall, this downward trend doesn’t seem to apply to women 35 to 44 years of age. In fact, coronary artery disease seems to be on the rise in this group; however it is still very rare.”

Schmiegelow acknowledged that this evaluation was limited to women who had given birth, but added her belief that the findings are applicable to other young, healthy women in Denmark and elsewhere.

“The obesity epidemic is exploding, and we saw the urgent need to examine whether obesity increases the risk of cardiovascular disease in young women,” Schmiegelow said. “Based on our findings, we need to focus more attention on the heart health risks associated with obesity early in life, especially given that obesity and heart disease both increase with age.”

According to Schmiegelow, the Danish study is the largest to date, and gives investigators “a better glimpse” into the role of obesity and cardiac events at younger ages. Previous studies have typically involved women older than 45 years. The researchers also found that women who were underweight were slightly more prone to having a heart attack or stroke as well, although this trend needs to be further investigated.