Based on the best available evidence:
Approximately 1 in 3600 to 4000 males in the world are born with the full mutation for Fragile X. The vast majority of males with the full mutation will have an intellectual disability.
Approximately 1 in 4000 to 6000 females in the world are born with the full mutation for Fragile X. About 50% of females with the full mutation will have some features of fragile X syndrome and a varying degree of intellectual disability.
Approximately 1 in 800 men in the world are carriers of the Fragile X pre-mutation.
Approximately 1 in 260 women in the world are carriers of the Fragile X pre-mutation. (Though a 2004 analysis suggests that the figure could be as high as 1 in 130.)
For more information about what it means to be a carrier of Fragile X please see this link: http://www.fragilex.org/fragile-x-associated-disorders/carriers/
Researchers from the University of Wisconsin-Madison’s Waisman Center, together with researchers from the Centers for Disease Control and Prevention (CDC), have published a new study describing the number of people who have a premutation in their FMR1 gene. You can read the abstract of the article here. http://www.ncbi.nlm.nih.gov/pubmed/22619118
This study is the first to report the frequency of the fragile X premutation among a group of people in the United States. This study on older adults reports data about symptoms often associated with fragile X-associated disorders.
Main Findings from This Study http://www.cdc.gov/ncbddd/features/fxs-prevalence-keyfindings.html
This study showed a higher number of people having a premutation in the FMR1 gene than was found in previous research. This study also suggested that people with a fragile X premutation are more likely to report symptoms associated with fragile X-associated disorders. Having a fragile X premutation can pose challenges at all ages.
As reported in this paper, the frequency of fragile X premutation was as follows:
0 1 in 151 females, or about 1 million women in the United States.
1 1 in 468 males, or about 320,000 men in the United States.
These statistics are important because both men and women are at risk for having symptoms linked to fragile X-associated disorders.
Women with a premutation reported their last menstrual cycle at an earlier age than women without a premutation (48 vs. 51 years).
Men and women with a premutation were more than four times as likely to report dizziness or fainting as people without a premutation (18% vs. 4%).
Men and women with a premutation were more than twice as likely to report numbness as people without a premutation (29% vs. 13%).
Twenty-three percent of people with a premutation had a child with a disability.
Twelve percent of people without a premutation had a child with a disability.
Prevalence and Instability of Fragile X Alleles (Cronister, et al)