Under-estimation of alcohol consumption among women at-risk for drinking during pregnancy.

Over recent years, researchers have heeded the call for improved measures of alcohol consumption and have begun to develop more sophisticated methodologies to assess actual use for both general populations (Dawson, 2003; Kerr, Greenfield, Tujague & Brown, 2005; Martin & Nirenberg, 1991; Midanik, 1982; Miller, Heather & Hall, 1991; Williams, Proudfit, Quinn & Campbell, 1994; Wilson, 1981) and specialized populations, such as pregnant and parenting women (Ernhart, Morrow-Tlucak, Sokol & Martier, 1988; Russell, Chan & Mudar, 1997). For example, an earlier study with uninsured pregnant urban women found that when drink size was considered, average daily volume during pregnancy increased to the risk level for fetal alcohol syndrome (Kaskutas, 2000). This article offers further evidence that drink size should be an important element in assessing potential risk. We focus specifically on an insured population of childbearing-aged females identified as at-risk for drinking during pregnancy by their prenatal care provider.

Historically, a common practice in national survey research (and a practice often used in smaller clinical studies) has been to instruct respondents to report the quantity and frequency of their alcohol intake over some reference period (Greenfield, 2000; Room, 1990). Alcohol use questions are usually prefaced with a definition of a "standard drink;" for example, "a 12-ounce can of beer, a 4-ounce glass of wine or a 1-ounce shot of liquor" (Alcohol Research Group, 1964-2005; Greenfield, Midanik & Rogers, 2000; Stockwell, Donath, Cooper-Stanbury, Chikritzhs, Catalano & Mateo, 2004), or "a can or bottle of beer, a glass of wine or a wine cooler, a shot of liquor, or a mixed drink with liquor in it" (Office of Applied Studies, 2005). In this case, respondents are required to make quick mental translations to estimate the actual number of "standard drinks" they drink based on the size and alcohol-concentration across all beverages consumed. Other surveys ask respondents to report the number of ounces in their typical drinks for specific beverages (National Institute on Alcohol Abuse and Alcoholism, 2004). Both methods assume that respondents can conceptualize how much a fluid ounce is, an assumption challenged by a growing number of studies showing otherwise (Graves, Kaskutas & Korcha, 1999; Stockwell, et al., 2004; Wansink & van Ittersum, 2005; White, Kraus, Flom, Kestenbaum, Mitchell, Shah, et al., 2005).

To achieve more accurate consumption estimates, researchers have responded in innovative ways, for example, by asking respondents to designate their usual pour level for drinking vessels depicted in life-size photographs (National Institute on Alcohol Abuse and Alcoholism, 2004); or from a selection of actual glasses, bottles, and cans augmented by an array of vessel photographs (Kaskutas & Graves, 2000; Russell, Marshall, Trevisan, Freudenheim, Chan, Markovic, et al., 1997); or by asking respondents to first pour liquid into the glass they usually use for a particular beverage and then having them pour the liquid into a measuring beaker (Banwell, 1999; Carruthers & Binns, 1992; Kerr et al., 2005; Lemmens, 1994). These methods consistently reveal that actual alcohol consumption is underestimated (especially for higher ethanol content beverages and drinks that are poured from larger containers) such that standard drinks should be recalculated using mark-ups that reflect this under-reporting.

Table 1 displays recommended mark-ups for published studies that have looked specifically at drink size. These mark-ups appear to be culturally and demographically influenced. Reviewing across these studies, we found suggested mark-ups ranging from 1.25 for beer, 1.95 for wine, and 2.0 for spirits among drinkers ages 12 and older in New Zealand (Fryer, Kalafatelis, McMillen & Palmer, 2004); around 1.04 for wine, 1.14 for fortified wine, and 1.26 for spirits among at-home Dutch drinkers (Lemmens, 1994); 1.92 for wine and 2.30 for spirits drinkers among employed Scottish drinkers (Gill & Donaghy, 2004); 1.3 for wine, 2.0 for spirits, 2.8 for malt liquor, and 2.7 for fortified wine among U.S. poor minority inner-city females (Kaskutas & Graves, 2000); 1.25 for beer, 1.50 for wine and 1.26 for spirits among college students in the U. S. (White, Kraus, McCracken & Swartzwelder, 2003); and 1.24 for any drinks consumed from barware glasses (Wansink & van Ittersum, 2005).

One problem with comparing drink size estimates across these studies is that there are no consistent definitions for standard drink sizes. For example, in the ten studies reviewed (see Table 1 notes) we found that standard drink sizes were described as grams of ethyl alcohol ranging from 8 to 14 grams, or as ounces of absolute alcohol with standard spirit drink size portions ranging from 1 to 1.5 ounces. Only one study adjusted for the differences in the alcohol concentration for specific beverage types (Kerr, et al., 2005). In the U.S., the percentage of alcohol by volume (% ABV) for beer typically ranges from 4.3 or less (including light beers) to 5.0 or higher for the popular Budweiser brand and microbeers (Kerr, et al., 2005). Further, white table wines have a lower % ABV on average than red wines and moreover, the U.S. government labeling regulations allow the reported % ABV to vary by 1.5 percentage points in either direction (Kerr, Greenfield, Tujague & Brown, 2006). However, putting measurement issues aside, the findings show a consistent trend across studies--actual drink size portions tend to be larger than actual standard drink size portions.

While the magnitude of the difference between actual and standard drinks sizes may initially appear inconsequential, these differences can take on significance under specific circumstances, such as when making recommendations about general health practices and consumption (U. S. Department of Agriculture, 2000), accurately reporting epidemiologic consumption patterns over time (Kerr, et al., 2006), and determining safe drinking as related to social consequences like driving under the influence (Dawson, 2003; World Health Organization, 2000). Further, precise measurement of alcohol intake can be especially important for assessing potentially high-risk situations where the likelihood for harm may be high and the possible effects of an intervention particularly beneficial. This article uses data from one such intervention (called Early Start Plus) to examine the differences between actual and standard size portions reported by childbearing-aged women identified as at-risk for drinking during pregnancy.

The Early Start Plus intervention, which was implemented in 7 of 15 specialized Early Start prenatal care clinics (Armstrong, Lieberman, Carpenter, Gonzales, Usatin, Newman, et al., 2001) belonging to a large private nonprofit managed care health organization, sought to reduce negative neonatal and maternal outcomes by using drink size as a way of creating dialogue about pregnancy drinking. The intervention helped pregnant women recognize how much they actually drank, using calibrated glassware and other beverage containers along with computer graphics designed to define true volume for specific alcoholic beverage types (Witbrodt, Kaskutas, Korcha & Armstrong, 2007). The intervention promoted abstinence, however, if that was not an obtainable goal, women were taught ways to cut down as much as possible during the remainder of their pregnancy.