Authors: Jessica Klusek, Jinkuk Hong, Audra Sterling, Elizabeth Berry-Kravis, and Marsha Mailick


Drs. Jessica Klusek, Marsha Mailick, and colleagues investigated how a dimension of executive function, inhibition, is affected by age and FMR1 CGG repeats among mothers of children with Fragile X syndrome. Inhibition is the ability to suppress an action, such as not eating that piece of chocolate even though you really want it. Difficulties with inhibition can affect relationships and are linked to mental health problems. This study looked at relationships between inhibition, measured in two different ways, and individual factors, such as age and the FMR1 gene, among female premutation carriers.

This study included 134 premutation carriers who were mothers of children with Fragile X syndrome. Participants completed a test over the phone called the Hayling Sentence Completion Test, which directly measures verbal inhibition (i.e., how quickly and accurately a participant completes a sentence). Separately, participants answered questions about daily tasks associated with inhibition, such as waiting your turn. FMR1 CGG repeat length was also measured.

On the Hayling test, greater difficulties with inhibition were associated with older age. Additionally, individuals who had CGG repeats between 80 and 90 had greater difficulties with inhibition compared to individuals with who had 90–115 CGG repeats. On the questionnaire, participants with 90–110 CGG repeats reported the greatest difficulties with daily activities of inhibition.

Why This Matters

This study highlighted that older mothers of children with Fragile X syndrome (over 70 years) who have “mid-range” CGG repeats (~80–100) may be at increased risk for difficulties with inhibition. The mid-range has been previously associated with risks for mental health problems and FXPOI, as well as increased vulnerability to stress, suggesting important implications for these individuals’ health and well-being.

Next Steps

Researchers would like to better understand how age-related differences in inhibition may be associated with changes in the brain. Such information may provide insight into FXTAS and the role of the FMR1 gene in aging.

Funding: This work was supported by the National Institutes of Health under grant numbers R01HD082110, P30 HD003100-S1, U54 HD090256, R21DC017804, R03HD098291.

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