Children born with congenital heart disease (CHD) in Sweden in the early 1990s had a lower mortality rate than those born in the 1970s, according to a registry-based, prospective, matched-cohort study.

Still, after a mean follow-up period of 27.0 years, the mortality risk was nearly 17 times higher in children and young adults with CHD compared with a matched control group.

Lead researcher Zacharias Mandalenakis, PhD, of Sahlgrenska University Hospital in Sweden, and colleagues published their results online in JAMA Internal Medicine on Dec. 19.

Approximately 1 percent of babies are born alive with CHD, according to the researchers. They added that CHD is one of the leading causes of death during infancy and childhood.

For this analysis, they evaluated 21,982 patients born between January 1970 and December 1993 who were diagnosed with CHD and registered in the Swedish National Hospital Inpatient Register and the National Hospital Outpatient Register. The median age at index registration was 4.22 years old, while 48.4 percent of patients were females.

The researchers then matched each patient by birth year, sex and county with 10 control individuals who were not diagnosed with CHD.

They found that 1,673 patients with CHD died during a mean follow-up period of 27.0 years and 1,077 patients in the control, non-CHD group died during a mean follow-up period of 28.5 years.

The mortality risk was 16.51 times higher in patients with CHD compared with the control group. Patients with the most severe complex defects had the highest mortality risk.

The mortality rates were higher in patients with CHD compared with controls in all age and birth cohort groups. The highest mortality risk was found in children younger than 5 years old in all birth cohorts, although survivorship among children younger than 5 years old increased from 96 percent for those born in 1970-1979 to 98 percent for those born in 1990-1993.

The researchers mentioned that the relative and absolute mortality risks declined with increasing age and by increasing birth decade, although mortality was still high during adolescence.

They also noted that the probability of death until age 42 was 12 percent in patients with CHD and 2 percent in the control group. In addition, the mortality rate was significantly higher in the first four years after birth and continued to increase at a lower rate during adulthood.

For men, the cumulative survival was 87 percent in patients with CHD and 98 percent in the control group. For women, the cumulative survival was 90 percent and 99 percent, respectively.

Among patients with CHD, the cumulative mortality at 18 years old was 4 percent in those born in 1990-1993 compared with 6 percent in patients born in 1980-1989 and 8 percent in patients born in 1970-1979.

The study had a few limitations, according to the researchers, including that it only relied on registries and that the outpatient registry only had data available since 2000. They also noted there was no formal validation of diagnoses. In addition, there were three versions of ICD codes used during the study, which could have led to difficulties in comparing patients with CHD in different eras.

“There was a significant reduction in the mortality rate in patients with CHD between 1970 and 1993, predominantly as a result of declining early deaths,” the researchers wrote. “However, although the mortality risk has decreased by more than 100 times, children with CHD younger than 5 years and born in the early 1990s still have a mortality risk more than 33 times higher than the risk in children without CHD. Our results indicate the need for research on the mechanisms of death in this group of young patients.”