The Impact of Maternal Age on the Effects of Prenatal Alcohol Exposure on Attention

THE FETAL ALCOHOL spectrum disorders (FASD; Bertrand et al., 2004; Hoyme et al., 2005; Sokol et al., 2003), including fetal alcohol syndrome (FAS), include specific neural and craniofacial malformations, growth restriction, and neurobehavioral and cognitive deficits (Hoyme et al., 2005; Kodituwakku, 2007; Nash et al., 2006; Sokol et al., 2003; Spadoni et al., 2007). The estimated incidence of FAS ranges from 0.3 to 2.0 per 1,000 live births in the general population (CDC, 2002a, 2002b; May and Gossage, 2001), with a higher incidence among certain groups depending upon socio-demographic, behavioral, clinical, and other risk factors (Abel, 1995; CDC, 2002a, 2002b; May et al., 2007, 2008). The combined incidence of all FASD is higher and estimated at about 10 per 1,000 live births (Manning and Hoyme, 2007; O’Leary, 2004; Sampson et al., 1997). While awareness of the risk of alcohol use during pregnancy has increased substantially since 1989 when warning labels began to appear on alcohol beverage containers, more than half of women of child-bearing age continue to consume alcoholic beverages, and over 11% report continued drinking during pregnancy (CDC, 2009; Stratton et al., 1996). The rates of certain patterns of consumption that put fetuses at greater risk for FASD, especially self-reported binge drinking—defined as 5 or more drinks per occasion (CDC, 2002a, 2002b)—have remained essentially unchanged at around 2% since 1991 (CDC, 2009). However, levels of drinking also vary with maternal age. Older pregnant women (>34 years old) are 37% more likely to report drinking during pregnancy than younger women (CDC, 2009). However, self-reported rates of binge drinking were not significantly different between younger pregnant women (18 to 24 years old), at 2.5%, and older pregnant women (>34 years old), at 1.8%(CDC, 2009). In this paper, we are examining attention problems because they are among the more frequently reported outcomes associated with FASD (Brown et al., 1991; Carmichael Olson et al., 1998; Coles et al., 1997; Fryer et al., 2007; Kodituwakku, 2007). Deficits have been identified in sustained attention (Coles et al., 2002; Lee et al., 2004), as well as executive function, memory, IQ, fine motor skills, and other neurodevelopmental domains (Coles et al., 1997; Kodituwakku, 2007; Kodituwakku et al., 1995; Mattson et al., 1998). Coles and colleagues (1997) reported other alcohol-related attention deficits in visual / spatial skills, encoding of information, and flexibility in problem solving. Yet there are inconsistencies in the occurrence of attention problems and hyperactivity in prenatal alcohol-exposed children. Nanson and Hiscock (1990) reported increased hyperactivity and slower reaction times, while Roebuck and colleagues (1999) and Coles and colleagues (1997) did not.Carmichael Olson and colleagues (1992) found deficits in focused attention but not as severe as those found in children diagnosed with attention deficit hyperactivity disorder (ADHD). These variations in reported attention deficits may be related to multiple factors including which prenatal alcohol exposure variable was assessed, differential difficulty of the task assessing attention (Kodituwakku, 2007), sample size, or additional moderating variables, such as maternal age. In addition to maternal age and how risk drinking is assessed, several other factors are influential in the variable expression of attention effects in FASD and ADHD, such as how attention is measured and cohort characteristics (e.g., age, demographics, etc.). These are considered further in the Discussion. Alcohol-related neurobehavioral deficits are certainly also influenced by differences in vulnerability and individual susceptibility, even at comparable levels and rates of maternal drinking. The variable expression of prenatal alcohol-related effects may be because of differential genetic susceptibility, exposure periods, or drinking patterns (Abel, 1995; American College of Obstetrics & Gynecology, 2006; Chiodo et al., 2009; Ernhart et al., 1987; Henderson et al., 2007; Jacobson and Jacobson, 1994, 1999; Maier and West, 2001; Martinez-Frias et al., 2004; NIAAA, 2005a; Olney, 2004; Sokol et al., 1986; Stratton et al., 1996; West et al., 1994), as well as nutritional or other risk factors. One factor that may influence the impact of prenatal alcohol on neurobehavioral outcome is the pattern of alcohol consumption. Detection of patterns of maternal drinking that place fetuses at risk for FASD is critical to diagnosis, treatment, and prevention but is challenging and often insufficient during pregnancy. We recently showed that outcomes depend on which measure of prenatal alcohol exposure is used and that a metric that accounts for several different measures of risk-level drinking during pregnancy is a better predictor of neurobehavioral effects of prenatal alcohol, including focus and divided attention, than the individual alcohol consumption measures alone (Chiodo et al., 2010). Older age appears to be another maternal characteristic that is related to differential susceptibility to the effects of prenatal alcohol exposure. Jacobson and colleagues (1998, 2004) and Burden and colleagues (2005) showed greater adverse performance in attention and working memory tasks for infants and children born to older drinking mothers (≥30 years old) compared to younger mothers (Burden et al., 2005). Prenatal alcohol exposure-related deficits in working memory were greater among children born to women ≥30 years of age. Despite a small sample, children born to older mothers performed significantly-worse in 4 of 7 measures of attention, memory and general cognitive ability. For example, there were increased errors of omission in a Digit Cancellation task, working memory deficits in the digit span test, and lower scores on the Wechsler Intelligence Scale for Children–Revised (WISC-R) Arithmetic subscale, and others, while only one outcome—executive function measured by the Tower of London task—was significantly impaired for children whose mothers were