Did raising the drinking age reduce veterans later alcohol treatment episodes? The U.S. military as a natural experiment Amy Wallace, MD, MPH Atticus Wallace Edward Sheehan, MD Yinong Young-Xu, ScD William Weeks, MD, MBA VA Office of Rural Health, Rural Health Resource Center Eastern Region VA Outcomes Group REAP The Dartmouth Institute Washington and Lee University
Background Early alcohol exposure may lead to: Neuroanatomical changes Decreased hippocampal volume Neurocognitive impairment Risky sexual behaviors, injury (e.g. by MVA) or premature death (accident, suicide) Increased vulnerability to later AUDs
Based on what data? Observational studies in human adolescents Possible confounders for adolescents who drink early include genetic predisposition toward AUDs adverse environmental factors Randomized controlled trials Consistent with observational studies One problem (RATS!)
Adolescent rats Rats may not behave exactly like humans
GAPS What are the relative contributions of genetics and environment versus exposure per se? If early exposure per se is a risk factor, when is drinking safe? Is a 13 year old like an 18 year old?
U.S. Military natural experiment? Pre-1982 US soldiers could drink on base regardless of age Discounted alcohol was sold on base Alcohol was provided to troops in the field after stressful events
1982-88 1982 and beyond Bases conformed to state drinking age laws Post-1988 Drinking age for soldiers on US bases was 21 Zero tolerance policies established for underage and problem drinking Early detection and prevention programs created Alcohol was deglamorized
Was reducing alcohol exposure during late adolescence for soldiers associated with changes in later problem drinking? Using treatment episodes as a proxy for later AUDs: Compare vets from age groups with different exposures across years spanning changes in drinking age Compare vets to same-age civilians
Methods: Treatment Episode Data Set (TEDS)* Data were collected on all clients entering any addiction treatment at publicly funded programs. 67% of the total known admissions. Doesn t include VA. Years 1992-2003 Four age groups: 25-29, 30-34, 35-39, 40-44 *United States Department of Health and Human Services. Substance Abuse and Mental Health Services Administration. Office of Applied Studies
LegalTeenage Alcohol Exposure Why these years? Alcohol abuse/ dependence Birth year ages 18-20 ages 25-29 ages 30-34 ages 35-39 ages 40-44 Civilians 1948 1966-68 1988-1992 1958 1976-78 1988-1992 1993-1997 1998-2002 1968 1986-88 1993-1997 1998-2002 2003-2007 1978 1996-98 2003-2007
LegalTeenage Alcohol Exposure Why these years? Alcohol abuse/ dependence Birth year ages 18-20 ages 25-29 ages 30-34 ages 35-39 ages 40-44 Veterans 1948 1966-68 1988-1992 1958 1976-78 1988-1992 1993-1997 1998-2002 1968 1986-88 1993-1997 1998-2002 2003-2007 1978 1996-98 2003-2007
Methods-cont d All treatment episodes with alcohol flag Males and females analyzed separately Obtained veteran status from TEDS Denominators for rates US Census age group and years VetPop age group and years Veteran exposure proportion by state base population
Assumptions: Military recruitment at age 18 lasting through at least age 20 (three years potential exposure) Ages equally distributed within age group for treatment episodes and age group denominators Exposure to lower drinking age on non-us bases non-contributory US base populations by state used to model military population exposure
Results: (ages 25-44, years 1992-2003) Males: 446,763 alcohol treatment episodes for 65 million male veterans 3.3 million alcohol treatment episodes for 434 million male civilians Females: 28,083 alcohol treatment episodes for 756,000 female veterans 1.5 million alcohol treatment episodes for 444 million female civilians
Males: Treatment episode rate per 1000 by year and age group 12 Ages 40-44 Veterans' alcohol treatment episode rates 300% 12 Ages 35-39 300% 10 Civilians' alcohol treatment episode rates Veteran population exposure to legal drinking Civilian population exposure to drinking age under 21 250% 10 250% Treatment Episodes per 1000 8 6 4 2 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 200% 150% 100% 50% 0% Legal <21 drinking exposure Treatment Episodes per 1000 8 6 4 2 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 200% 150% 100% 50% 0% Legal <21 year drinking exposure Treatment Year 12 Ages 30-34 300% 12 Ages 25-29 300% 10 250% 10 250% Treatment Episodes per 1000 8 6 4 2 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 200% 150% 100% 50% 0% Legal <21 year drinking exposure Treatment Episodes per 1000 8 6 4 2 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 200% 150% 100% 50% 0% Legal <21 year drinking exposure Wallace et al Military Medicine July 2008
Odds ratios of alcohol treatment episodes and exposure to legal <21 year drinking for male veterans vs. civilians by age group 1.4 Male veterans age 25-29 300% 1.2 Male veterans age 30-34 Male veterans age 30-34 Male veterans age 35-39 Male veterans age 35-39 Male veterans age 40-44 Male Male veterans civilians age (corresponding 40-44 age cohort ref group) 250% Veterans Male civilians under 21 (corresponding drinking exposureage cohort ref group) 1.0 Civilians under 21 drinking exposure Under 21 year age exposure 200% Odds Ratio 0.8 0.6 0.4 0.2 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year 150% 100% 50% 0% Under 21 drinking age exposure Wallace et al Military Medicine July 2008
Females: Lower drinking rates than males Abuse: 26/1000 vs. 69/1000 for men Dependence: 23/1000 vs. 54/100 for men Genetic factors ~ 50% Environmental factors ~ 50% Male-dominated work environments Negative life events Female soldiers/veterans higher AUD risk
Females: Treatment episode rate per 1000 by year and age group 7 Females 40-44 years old 300% 7 Females 35-39 years old 300% 6 Veterans Civilians Veteran population exposure to legal under 21-year drinking 250% 6 250% Treatment rate per 1000 5 4 3 2 1 0 Civilian population exposure to legal under 21-year drinking 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year 200% 150% 100% 50% 0% Legal under 21 year MLDA exposure Treatment rate per 1000 5 4 3 2 1 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year 200% 150% 100% 50% 0% Legal under 21 year MLDA exposure 7 Females 30-34 years old 300% 7 Females 24-29 years old 300% Veterans 6 250% 6 Civilians Veteran population exposure to legal under 21-year drinking 250% Civilian population exposure to legal under 21-year drinking 5 5 Treatment rate per 1000 4 3 2 1 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year 200% 150% 100% 50% 0% Legal under 21 year MLDA exposure Treatment rate per 1000 4 3 2 1 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year 200% 150% 100% 50% 0% Legal under 21 year MLDA exposure Wallace et al Journal of Women s Health (inpress)
Odds ratios of alcohol treatment episodes and exposure to the legal <21 year drinking for female veterans vs. civilians by age group Treatment Year 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 5 350% Female veterans age 25-29 Odds ratio for alcohol treatment 4 3 2 1 0-1 -2 Female veterans age 30-34 Female veterans age 35-39 Female veterans age 40-44 Female civilians (corresponding age cohort ref group) Veterans under 21 drinking exposure Civilians under 21 drinking exposure 1992 1993Female 1994 veterans 1995 age 25-291996 1997 1998 1999 2000 2001 2002 2003 300% 250% 200% 150% 100% 50% 0% Exposure to under 21 year MLDA Female veterans age 30-34 Treatment Year Wallace et al Journal of Women s Health (inpress)
Conclusions: Changes in drinking age and military environment were associated with reduction in later alcohol treatment episodes for vets The greater the exposure to 21-year drinking age/enforcement, the greater the difference between: Veterans compared to same-aged civilians Veterans within age groups pre- and post- military drinking changes 1992 vet rates> civilian rates By 1998, all vet rates<civilian rates (exposure to under 21 drinking age ~50%)
Limitations VA treatment? Cutbacks in late 1990s likely mean steeper curves Treatment episodes per 1000 enrolled vets 12 10 8 6 4 2 0 35-39 year olds 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 300% 250% 200% 150% 100% 50% 0% Under 21 year drinking age exposure
Limitations continued Reliance on observational data advantages over prior studies Random comparison groups (pre-post environment changes) Large sample Assumptions may be erroneous Other environmental or military cohort factors may be responsible
Implications Legal drinking age should not be lowered Other supervised settings (college campuses) should consider following the military s example Find the happy medium.
Questions? Acknowledgements VAMC Outcomes Group REAP HSRD Research Career Development Program