RESULTS

Sixty-six percent of respondents (N=27,081) ever drank alcohol, 49 percent before age 21 and 3 percent before age 14. The mean drinking onset age was 19 years. Thirteen percent of the sample (N=5368) were diagnosed as being alcohol dependent ever in their life and 4 percent in the past year (N=1713). Twenty-five percent reported a family history of alcoholism (N=10481). In the past year five percent (N=2,082) of respondents reported drinking 5+ drinks in a single day at least once per week and 1 percent (N=635) reported drinking enough to get drunk at least once per week. During their period of heaviest drinking, seventeen percent (N=7198) reported consuming five plus drinks on an occasion at least weekly and four percent (N=1608) did so everyday. 

Fifteen percent (N=3,933) of those who ever drank reported having been in a situation after drinking that increased their chance of injury ever in their lifetime, and 3 percent (N=776) in the past year. Eight percent of those who ever drank (N=2150) reported accidentally injuring themselves under the influence of alcohol ever in their life and two percent (N=378) in the past year.

Respondents who began drinking at younger ages were much more likely than those who did not start drinking until they were 21 or older to report heavy drinking both in the year prior to the survey and during their period of heaviest drinking. Those whose drinking began prior to age 14 were more than 3 times more likely to report consuming 5 or more drinks on a single day at least once per week during the past year, 16 percent vs. 5 percent. They were 7 times more likely to report drinking enough to be intoxicated at least once per week, 7 percent vs. 1 percent (Figure 1). Further, they were five times more likely to report drinking 5+ daily during their period of heaviest drinking 26 percent vs 5 percent.

Early age of drinking onset was also strongly related to both being in situations while or after drinking that increased a person's chances of being injured and being accidentally injured under the influence of alcohol. Compared to respondents who began drinking at age 21 or older, those who began drinking prior to age 14 were nearly 7 times more likely to report having been in situations that increased their chance of injury, ever in their life 34% vs. 5% and in the past year 7% vs 1% (Figure 2). Further, persons drinking prior to age 14 were 12 times more likely to have ever been accidentally injured under the influence of alcohol ever in their life 24% vs. 2%, and at least 10 times more likely to have been injured this way in the past year, 5% vs. 0.4% (Figure 3). 

Relationships between age of drinking onset and measures of frequency of heavy drinking as well as exposure to situations posing risk of injury and injury involvement were monotonic from drinking onset at age 14 to age 21 and older. The younger respondents were when they began drinking, the greater the frequency of heavy drinking and experiencing injuries after drinking.

Frequent heavy drinking in the past year and during the period when respondents drank most was associated with greater risk of injury involving alcohol. To illustrate, 29 percent who drank to intoxication at least weekly in the past year were in a situation that year after drinking that posed a risk for injury (N=186/635) compared to 3 percent of drinkers who never drank to intoxication in the past year (N=63/19008) (p<.001). Seventeen percent who drank to intoxication at least once per week in the past year were injured under the influence of alcohol in the past year (N=110/635) compared to 0.1 percent of lifetime drinkers who never drank to intoxication in the past year (N=14/19008) (p< .001). In addition, several subgroups in the study were significantly more likely to have begun drinking at earlier ages: male respondents, younger respondents, those with less than a high school education, persons never married, persons who currently or ever smoked or used illicit drugs, persons who were currently or ever alcohol dependent and respondents reporting a family history of alcoholism (all relations p<.001; data available upon request).

The regressions examining the relation between age of drinking onset and drinking behavior are presented in Table 1. They revealed that after controlling for diagnoses of alcohol dependence and other variables related to age of drinking onset, the younger respondents were when they started drinking, the more likely they were in the past year to drink 5+ on an occasion and to drink to intoxication at least once per week. Compared to those who began drinking at age 21 or older, those who began before age 14 were nearly 1.4 times more likely to drink 5+ drinks and 2.8 times more likely to drink to intoxication at least weekly in the past year. They were also 3.1 times more likely to consume 5+ drinks daily during their lifetime period of heaviest drinking.

Tables 2-3 present results of regression analyses examining the relation between age of drinking onset and injury outcomes. The regression analyses on injury outcomes (not including alcohol dependence and drinking measures) revealed that even after controlling for other personal characteristics associated with age of drinking onset, respondents who began drinking before age 14 relative to those who started at age 21 or older were 5.0 times more likely to have ever been in a situation after drinking that increased their risk of injury and 3.2 times more likely to have done so in the past year (Table 2, Models 1a, b). They were also 4.8 times more likely to have ever been injured under the influence of alcohol and 2.4 times more likely to have been injured this way in the past year (Table 3, Models 1a,b). Even when we included in the regressions, measures of alcohol dependence, frequency of drinking 5+ during a respondent's period of heaviest drinking and past year frequency of drinking 5 + or to intoxication (each of which were independently related to our study outcomes), those who began drinking prior to age 14 relative to those who started at age 21 or later were 3.0 times more likely ever and 1.5 times more likely in the past year to have been in a situation after drinking that increased their risk of injury (Table 2, Models 2a,b). They were also 3.0 times more likely ever and 2.0 times more likely in the past year to have been injured under the influence of alcohol (Table 3, Models 2 a, b).

Further, lifetime elevated injury risks were not confined only to those who began drinking before age 14. Persons who began drinking in each age group under 21 relative to those who started when they were 21 and older were significantly more likely during their lives to have ever been injured under the influence of alcohol and to have placed themselves in situations after drinking that increased their risk of injury. This was found even after controlling for history of alcohol dependence, frequency of heavy drinking during respondents heaviest drinking period and numerous other characteristics related to age of drinking onset (Tables 2-3, Model 2a).

Our analyses also indicated that a large part of the relation between early age of drinking onset and unintentional injury under the influence of alcohol in the past year resulted from those who began drinking at an early age reporting more frequent heavy drinking in the past year. Persons who began drinking in each age group 17 and younger were significantly more likely than those starting at age 21 and older to have been injured after drinking in the past year when we controlled for the initial set of characteristics related to age of drinking onset (Table 3, Model 1b). However, after further analytically adjusting for diagnosis of alcohol dependence and for frequency of drinking 5+ on an occasion or to intoxication in the past year, only those who began drinking before age 14 were significantly (2.0 times) more likely to have been injured in the past year under the influence of alcohol (Table 3, Model 2b). Diagnosis of current alcohol dependence and frequency of heavy drinking accounted for the significant relation of early drinking age onset to injury after drinking in the past year. Frequent heavy drinking in the past year, which is more common among those who started drinking early in life, is particularly problematic given the disproportionate willingness of people who began drinking early in life to place themselves in situations after drinking that increase their risk of injury (Table 2). Even after controlling for measures of current alcohol dependence, and past year frequency of drinking 5+ or to intoxication, persons who began drinking prior to age 18 were also significantly more likely than those starting at age 21 or older to place themselves in situations after drinking in the past year that increased their risk of injury (Table 2, Model 2b).

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