Associations of parental age at pregnancy with adolescent cognitive development and emotional and behavioural problems: a birth cohort in rural Western China.

Background: The relationship between parental age at pregnancy and offspring development in low- and middle-income countries remains unclear. We aimed to examine the associations of parental age at pregnancy with adolescent development in rural China.

Methods: We conducted a prospective birth cohort study of offspring born to pregnant women who participated in an antenatal micronutrient supplementation trial in rural Western China. Adolescent cognitive development and emotional and behavioural problems were assessed by using the Wechsler Intelligence Scale for Children-IV and the Youth Self-Report-2001, respectively. After accounting for the possible nonlinear relationships, we examined the linear associations between parental age (in years) at pregnancy and scores of adolescent cognitive development and emotional and behavioural problems by performing generalized estimating equations.

Results: Among 1897 adolescents followed from birth to early adolescence, 59.5% were male with a mean age of 11.8 (standard deviation (SD): 0.8) years. The mean ages of mothers and fathers at pregnancy were 24.6 (SD: 4.4) and 27.9 (SD: 4.1) years old, respectively. All the P values of the nonlinear terms between parental age and adolescent development in all domains were greater than 0.05. Each one-year increase in maternal age at pregnancy was associated with a 0.29-point (95% confidence interval (CI) 0.06, 0.52) increase in the full-scale intelligence quotient in early adolescence. After parental age was categorized into quartiles, the total behavioural problem scores of adolescents with fathers with an age in the fourth quartile (Q4) were 6.71 (95% CI 0.86, 12.57) points higher than those of adolescents with fathers with an age in the first quartile (Q1), with a linear trend P value of 0.01. Similarly, higher scores (worse behavioural problems) were observed for internalizing behavioural problems and other emotional and behavioural symptoms related to anxiety, withdrawal, social problems, thought problems and aggressive behaviour.

Conclusions: At conception, older maternal age was independently linked to better adolescent cognitive development, whereas advanced paternal age was independently associated with a greater risk of adolescent emotional and behavioral problems. These findings suggest that public health policies targeting an optimal parental age at pregnancy should be developed in the context of offspring developmental consequences.