Population based studies have shown that older paternal age is linked to Autistic Spectrum Disorders (ASD).Risk is thought to increase with maternal age also. Are these ( ie paternal and maternal age) independent risk factors ? Is age difference between parents also important ?
Sandin et al address this important question using combined population based cohorts from various countries set up as International Collaboration for Autism Registry Epidemiology (ICARE). Children were followed from birth to reported diagnosis of ASD. The cohort comprised of 5766794 births across Denmark, Sweden , Norway, Israel and Western Australia.0.54% of these children received a diagnosis of ASD and 0.18% had AD.
Independent effects: Increasing paternal age was associated with more ASD. Relative to fathers aged 20–29 years, fathers 50 years or older had a statistically significantly increased risk for offspring with ASD (RR=1.66 95% CI:1.49–1.85). Maternal age showed a U shaped relationship. Relative to mothers aged 20–29 years, mothers younger than 20 years had a statistically significantly increased risk for offspring with ASD (RR=1.18 95% CI:1.08–1.29. After 30 years, increasing maternal age increased risk of ASD.
Data also show evidence to combined effect as well. Risk was highest when both parents were older. Increasing age difference between parents also increased the risk. Lowest risk was shown by couples that generated the majority of births, specifically, 29–39-year-old fathers and 25–35-year-old mothers. Relative risk increased in all directions from this region as the parental age difference increased.
Limitations: We do not have information on confounding factors ( Socio economic status , parental psychiatric history, obstetric complications etc). For example: Individuals who are shy and aloof ( may be traits of ASD) ,can be be over represented in older parents)
Conclusions: Increasing paternal age as well as maternal age increase the risk of ASD.Increasing difference in parental age is also a risk factor.
Summary of the article:
Autism risk associated with parental age and with increasing difference in age between the parents.Sandin S, Schendel D, Magnusson P, Hultman C, Surén P, Susser E, Grønborg T, Gissler M, Gunnes N, Gross R, Henning M, Bresnahan M, Sourander A, Hornig M, Carter K, Francis R, Parner E, Leonard H, Rosanoff M, Stoltenberg C, Reichenberg A.Mol Psychiatry. 2016 May;21(5):693-700.