According to a new study, people with Down syndrome live twice as long today as they did in the early 1980s'. These patients have a lower than average risk of developing many forms of cancer.
The study by Quanhe Yang and colleagues published in this week's Lancet was based on data collected from death certificates between 1980 and 1995 in the US. The researchers found that the average age at death for the 10,800 reported to have Down syndrome increased from 25 years in 1980 to 50 years in 1995.
The researchers review that de-institutionalization and keeping children with their families, along with better treatments for common causes of death could have contributed to the better survival. As expected, Yang et al found that those with Down syndrome were more likely to have had congenital heart defects, dementia, hypothyroidism or leukemia.
By contrast, they found cancers other than leukemia and testicular cancer were "strikingly low" in people of all ages with Down syndrome. The researchers speculate that there could be a number of explanations for this finding including a reduced exposure to environmental factors that contribute to cancer risk and tumour-suppressor genes on chromosome 21.
Jill O'Connor of Down Syndrome Association of NSW predicts the new life expectancy findings are relevant to Australia. "Prior to 1970 most Down syndrome children were institutionalised at birth or soon after," she said.
"Respiratory illnesses which are common in children with Down syndrome would not have been treated as vigorously as in others, and they were on the bottom of the list for cardiac surgery until the mid 1980s. Growing up at home has meant better healthcare, better nutrition and a better lifestyle."
Down syndrome is caused by an extra copy of chromosome 21 and occurs in one in every 600 babies throughout the world. It is one of the most common known causes of intellectual disability. "Figures on the survival rate of people with Down syndrome are important to us as families but it's also socially important," said Jill O'Connor. "We now have a whole generation of children who have grown up at home and will become a generation of older people with Down syndrome."
"This is something that as a society we need to provide support and services for because a lot more children will now outlive their parents."