Metabolic Syndrome (MBS) involves a combination of medical conditions that lend towards cardiovascular disease and diabetes. These include abdominal obesity, hypertension (elevated blood pressure), hypercholesterolemia (high HDL cholesterol and triglycerides), and high resting glucose. Typically, three or more of these conditions together indicate the syndrome.
According to a 2002 JAMA study, approximately 24% of the adult US population fulfilled criteria for this MBS. What’s more, 71% of the population studied had one or more of these MBS-associated conditions.
The endocrine disorder, Polycystic Ovarian Syndrome (PCOS), shares strong links with MBS and is even believed to be due to underlying insulin resistance, which ultimately affects the function of the female reproductive system . For instance, Apridonidze et al. (2004) found that women with PCOS were almost twice as likely to fulfill criteria for MBS as compared to controls. Given its relationship with insulin resistance, PCOS also shares a strong relationship with Type 2 diabetes, since insulin resistance is essentially pre-diabetes.
In 2007, utilizing a small survey-based study, Baron-Cohen’s team found increased reported rates of specific testosterone-related disorders in high-functioning autistic females and their mothers. These conditions included conditions such as hirsutism (excess hair growth), irregular menstrual cycles, PCOS, and severe acne. Surprisingly, the researchers did not investigate other MBS-related conditions, such as diabetes or hypercholesterolemia.
In a related study, Tanne (2012) reported that obese women are 67% more likely to have a child with autism and 156% more likely to have a child with developmental delay. She also found that mothers with diabetes are 133% more likely to have a child with developmental delay, yet the relationship between maternal diabetes and autism did not reach statistical significance.
However, just this last month, Kosidou et al. (2015) report that there does indeed appear to be a relationship between PCOS and autism, though the specifics of that relationship are still only theoretical– often vacillating back and forth between the effects of glucose/insulin and androgens on development.
In a very large study including 23,748 autism cases and 208,796 controls matched by age, sex, and region of birth, the researchers found that mothers with a diagnosis of PCOS were 59% more likely to have a child with autism as compared to control mothers. When PCOS and maternal obesity were thrown into the mix, mothers were 113% more likely to have children with autism.
Of relevance to MBS, mother’s of autistic children were also more likely to have:
- Gestational Diabetes
- Maternal Diabetes Mellitus (Type 1)
- Higher Body Mass Index (BMI)
- Maternal Essential Hypertension
Other findings that support evidence reported in previous research include: the relationship between autism and older paternal age, pre-term birth and small gestational size, low APGAR scores (an indication of perinatal stress), lower family income, greater parental education, and a history of parental psychiatric illness. In addition, the team also found that mother’s of autistic children were more likely to have been born outside of Sweden, although the relevance of this finding is not discussed.
In short, it is likely that the endocrine arm of the Metabolic Syndrome is a risk factor for autism, although the mechanisms of action are still understudied. In my opinion, I think the relationship between MTOR activity and autism, as seen in the autism-related syndrome, Tuberous Sclerosis, could be an excellent place to start. There’s a large body of literature outlining abnormal MTOR activation downstream of nutrient overload (i.e., carbs), cellular stress, and insulin resistance [2, for example]. In short, aside from the roles of genetic propensity, our lifestyle habits may well be tipping the “autism boat” thereby adding to the oft-debated autism epidemic.