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Ten facts about Down syndrome

By Kaylie Foster



First discovered in 1866, Down syndrome is the most common genetic condition in the world. Down syndrome occurs in approximately 1 in 700 births and is characterized by the duplication of the 21st chromosome. People with Down syndrome have 47 chromosomes instead of the typical 46 [1]. Here are 10 facts you may not know about Down syndrome.

 

1.  There are three types of Down syndrome.


Trisomy 21 is the most common type of Down syndrome, occurring in 95% of cases. People with Trisomy 21 have an extra copy of the 21st chromosome in all of their cells. In 3% of cases, Down syndrome manifests as Translocation, where a part of chromosome 21 becomes attached to another chromosome rather than occurring twice. Two percent of cases have Mosaic Down syndrome, which means only some cells have an extra copy of the 21st Chromosome [2].

 

2.  Down syndrome was depicted in art as early as the 15th Century.

 

While Down syndrome was not introduced into medical literature until 1866, when English doctor John Langdon Down first published his description of Down syndrome, pottery and paintings from the 15th and 16th centuries show the facial features commonly found in those with Down syndrome [2]. These include almond-shaped eyes, a shorter neck, a flatter nasal bridge, smaller ears, and palms with only one crease [3].

 

3.  The name “Down syndrome” was not standardized until the 1970s.

 

Despite the first written description of the condition being published in 1866, the cause of Down syndrome was not discovered until the 1950s [1]. The name “Down syndrome” was standardized in 1975 [4]. Before then, the condition was called “mongolism” [3].

 

4.  Life expectancy for people with Down syndrome is increasing.

 

In 1950, the average life expectancy for a person with Down syndrome was 22. The age has now increased to 60, thanks to strides in research and technology that have helped our understanding of Down syndrome [5].

 

5.  People with Down syndrome are generally creative, caring, and independent.

 

Although Down syndrome causes developmental delays, people with Down syndrome still live fulfilling lives. The cognitive effects of Down Syndrome do not keep people with Down syndrome from living independently, excelling creatively, and working in fields where they can help others [1,5].

 

6.  Down syndrome creates a higher risk for other health conditions.

 

People with Down syndrome have an increased risk of experiencing hearing problems, ear infections, cataracts, and congenital heart defects [2]. Around 50% of children with Down syndrome are diagnosed with a heart defect [3]. Adults with Down syndrome are more likely to experience sleep apnea (due to their narrower airways and lower muscle tone), thyroid disease, and early-onset Alzheimer’s [2].

 

7.  People with Down syndrome and their families are vastly content.

 

Research shows that 96% of parents and siblings of a person with Down syndrome would not trade their relative for a child without Down syndrome. People with Down syndrome are overwhelmingly happy, 99% reporting they enjoy their lives [2].

 

8.  Some maternal factors may increase the likelihood of Down syndrome.

 

While Down syndrome occurs in babies born to mothers of all ages, the frequency of Down syndrome births increases with the mother’s age [4]. Down syndrome is not hereditary, with less than 1% of cases being passed from parent to child; however, it is likely passed recessively by parents who do not experience the condition [2,4]. Mothers who give birth to one child with Down syndrome are more likely to have a second baby with Down syndrome [4].

 

9.  Down syndrome is not linked to any race, class, or sex.

 

While some other disabilities are disproportionately diagnosed in certain races or sexes, the genetic nature of Down syndrome affects children from all walks of life. Cases occur in all races and among men and women across socioeconomic classes [5].

 

10.  Down syndrome is celebrated annually. 

 

March 21st (3/21) is recognized as World Down Syndrome Day, signifying the three copies of chromosome 21. People often wear mismatched socks on March 21 to show their acceptance and support of individuals with Down syndrome. Communities across the globe host events and celebrations to highlight the lives of those with Down syndrome every year [1].

 

Sources

[1] Ramirez, W. (2024, August 8). Down syndrome fun facts. DSANI. https://www.dsani.org/blog/2024/8/8/down-syndrome-fun-facts

[3] Connect the Dots Pediatric Therapy. (2025). 21 facts about down syndrome - connect the Dots Pediatric therapy. Connect the Dots. https://ctdpediatrictherapy.com/21-facts-about-down-syndrome/

[4] Pediatric Associates of Franklin. (2024, October 1). Twelve facts for down syndrome awareness month. Pediatric Associates of Franklin. https://www.pediatricsoffranklin.com/practice-news/twelve-facts-for-down-syndrome-awareness-month/#:~:text=With%20the%20great%20strides%20made,lead%20mitigation%20of%20some%20symptoms.

[5] Massachusetts Down Syndrome Congress. (2023, November 6). Facts about down syndrome. MDSC. https://mdsc.org/about-us/facts-about-down-syndrome/

 
 
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