Mothers of kids with disabilities might be more forgetful as they age than other mothers, according to a new study that suggests the stresses of parenting a disabled child wear on mothers’ minds over time.

Fathers of disabled children did not differ from fathers of non-disabled children in memory skills as they aged. And mothers with a strong support system, a sense of control and a history of regular exercise kept sharper than those without those attributes.

“Keeping quality friendship, sense of control for life and physically active lifestyle would help to protect these parents from accelerated cognitive aging,” said Jieun Song, a researcher at the Waisman Centre at the University of Wisconsin-Madison, who led the study.

When the mothers in the study had more trouble handling their disabled kids and were older, their memory was worse, the researchers note in Journals of Gerontology: Series B.

That’s not surprising, considering past research that has shown parents with disabled kids tend to feel more stressed and to have more psychological problems, like depression, than those with children without special needs, the researchers note.

“Because mothers of children with disabilities are usually more involved in childcare and housework than their spouses, it is likely that these mothers are more exposed to chronic stress and consequently at higher risks of cognitive decline compared with fathers of children with disabilities over the life course,” Song told Reuters Health in an email.

Song said she and her team wanted to study the cognitive effects of parenting kids with disabilities because of the prevalence of these children in the US, the longer lifespans of parents and the large cost to society.

The study used data from a large national survey of parents from 2004 to 2006, examining the history of 128 parents with disabled children and 512 without disabled kids (and who didn’t take care of other disabled children or adults). The kids in the first group had child-onset disabilities, such as attention deficit disorder/hyperactivity, autism, cerebral palsy, Down syndrome, epilepsy and intellectual or learning challenges.

Parents were tested on verbal memory and fluency, mental processing speed, reasoning, working memory and ability to switch their attention.

Physical health, physical activity, depression, sense of control, social support and negative parenting experience were also included in the analysis.

Most of the mothers were in their late 40s and early 50s, had about two years of college and about 85 percent were non-Hispanic white. The mothers of disabled kids tended to be much more depressed, in worse physical health and to feel they had less of a sense of control than mothers without disabled kids.

For instance, 18 percent of mothers of disabled children reported having been depressed in the 12 months prior to the study, compared with 7 percent of mothers without disabled kids.

Mothers of disabled children also had more problems handling their kids and had less support from friends than women without disabled children.

Among the women with disabled children, being white, more educated and having more social support were linked to significantly better memory and thinking.

Fathers with disabled kids had more negative parenting experiences than fathers whose kids were not disabled. But there were no significant differences in their cognitive functioning.

The researchers did not have information about the severity of the children’s disabilities, their ages, or about any disabilities or other health problems among the parents that might affect cognition. They acknowledge in their report that because they only looked at one point in time, they cannot say whether parenting a disabled child caused the memory differences they observed.

“One important aspect of this study was that having a sense of control and support from friends helped mitigate the impact of long-term caring for a child with a disability,” said Tamar Heller, who directs the Institute on Disabilities and Human Development at the University of Illinois at Chicago.

“Overall, their findings buttress the need for family support services and supports for families of individuals with disabilities,” said Heller, who was not involved in the study. “It shows significant disparities for this population making these services and supports a public policy priority.”

Heller noted that her own research has found that if families received enough help from support services, they were much less likely to experience “caregiving burden.”

She added, “When families are involved in consumer-directed programs where they can direct the supports provided to their families, they are more likely to experience less burden and feel a greater sense of parenting competence. This study reinforces these notions that personal control and support are important in reducing stress and potential consequent cognitive declines.”