Data and Statistics on Fragile X Syndrome

Facts about fragile X syndrome

• Fragile X syndrome (FXS) is the most common known cause of inherited intellectual disability.1
• FXS affects both males and females, although females often have milder symptoms than males.2
• The exact number of people who have FXS is unknown, but a review of research studies estimated that about 1 in 7,000 males and about 1 in 11,000 females have been diagnosed with FXS.3

• Among people affected with FXS, intelligence quotient (IQ) scores decline noticeably with age: Adolescents and adults consistently score lower on IQ tests than do young children.4

• Young children with FXS often take longer than their peers without FXS to reach early developmental milestones and to develop nonverbal communication (communication without words, typically through gestures, facial expressions, and body language).

• Boys with FXS have an average IQ score under 55, significantly lower than the average IQ score of the general population, which is 100.

Fragile X diagnosis

Parents are usually the first to notice symptoms of FXS at about 12 months of age for boys and 16 months of age for girls.5

• Parents reported repeat healthcare visits before their healthcare provider diagnosed developmental delay at an average age of 20 months for boys and 26 months for girls.
• Health professionals typically diagnosed FXS about 16 months after confirming a developmental delay.

The average age of FXS diagnosis by gender5 (as reported by parents):

About 4 in 10 families reported that they visited a health professional at least 10 times before their child was diagnosed with FXS.6

Co-occurring conditions and characteristics

A national parent survey found that most people with FXS had been diagnosed or treated for other conditions that occur together (co-occurring) with FXS.7

About 3 in 10 boys with FXS, but only 2 in 10 typically developing boys, are obese.8

Another study of 557 people with FXS between 3 and 21 years of age found that9

• Just over 4 in 10 people had both FXS and autism spectrum disorder (ASD).
• People with both FXS and ASD were about 3 times more likely to experience seizures than people with FXS alone.
• Approximately 4 in 10 people with both FXS and ASD had sleep problems that required treatment, compared with 3 in 10 people with FXS alone.
• Compared with children who only have ASD, children with both FXS and ASD may be less likely to receive behavior therapy.
• There was a higher proportion of attention problems, hyperactivity, hypersensitivity/over reactivity, perseverative/obsessive compulsive behavior, and irritability/aggressive behavior/agitation/ self-injury among those with both FXS and ASD as compared with those with FXS alone.

Adult life of men and women with FXS

Among adults with FXS, men are less likely than women to be able to read books with new words or ideas, speak using complex sentences, or speak at a typical speed.10

A national family survey of adults with FXS showed that11

• About 4 in 10 women with FXS achieved a high or very high level of independence in adult life compared with about 1 in 10 men.
• About 4 in 10 women with FXS lived independently, often with a spouse or romantic partner, compared with 1 in 10 men who lived independently, and rarely with a spouse or romantic partner.

Premutation

How many people have a fragile X premutation?

The exact number of people who have a fragile X premutation is unknown. Studies estimate that between 1 in 148 and 1 in 291 females and between 1 in 290 and 1 in 855 males in the United States may have a fragile X premutation.121314151617

These premutation estimate numbers are important because both men and women with a fragile X premutation are at risk for having symptoms related to fragile X-associated disorders.13

Findings among men and women with a fragile X premutation include

• Women with a premutation reported their last menstrual cycle at an earlier age (on average, 48 years) than women without a premutation (on average, 51 years).13
• Men and women with a premutation were more than four times as likely to report dizziness or fainting and more than twice as likely to report numbness compared with people without a premutation.13
• A national parent survey found that males and females with fragile X premutation were more likely to have been diagnosed or treated for other conditions that occur together with FXS compared with people who did not have a premutation.7

Quick Fact

Costs

A study analyzing the employment impact and financial burden experienced by families of children with FXS found that18

• With each additional condition occurring with FXS, there was greater financial burden for the family.
• About half of families reported that FXS caused a financial burden.
• In more than 6 in 10 families, parents changed work hours, stopped working, or turned down a job because of having a child with FXS.
• Families reported that therapies accounted for about one third of their FXS-related out-of-pocket expenses. An additional third of out-of-pocket expenses went to medicines and other medical costs, including genetic testing and developmental evaluations.