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Methods

The Alcohol-Related Disease Impact (ARDI) application provides estimates of alcohol-related harms including alcohol-attributable deaths (AAD), years of potential life lost (YPLL), and alcohol-attributable fractions (AAF).

Both AAD and YPLL are calculated using current population estimates of the total proportion of deaths for various causes that are attributable to alcohol use. These proportions, called AAF, were either measured directly or calculated indirectly on the basis of current scientific literature.

Alcohol-Attributable Fractions (AAF)


100% Alcohol-Attributable Conditions

Certain causes of death are, by definition due to alcohol consumption. These deaths are classified as being 100% alcohol-attributable and are reported in ARDI as having an AAF of 1.00. The following chronic causes of death are listed as 100% alcohol-attributable in ARDI: alcoholic psychosis, alcohol abuse, alcohol dependence syndrome, alcohol polyneuropathy, degeneration of the nervous system due to alcohol use, alcoholic myopathy, alcohol cardiomyopathy, alcoholic gastritis, alcoholic liver disease, fetal alcohol syndrome, fetus and newborn affected by maternal use of alcohol, alcohol-induced chronic pancreatitis. Three acute causes of death are 100% alcohol-attributable: alcohol poisoning, excessive blood alcohol level, and suicide by and exposure to alcohol.

Directly Measured AAF

For some causes of death, especially acute causes (e.g., injuries), ARDI uses direct estimates of AAF. These direct estimates are based on scientific studies that have directly measured the relationship between excessive alcohol use and a given health outcome. These estimates typically come from follow-up studies that included information obtained from medical record reviews, interviews with next-of-kin, or some combinations of these, that have directly assessed a decedent's pattern of alcohol consumption, or from studies that have assessed the proportion of persons dying from a particular alcohol-attributable condition that had a blood alcohol concentration (BAC) above a specified level (e.g., 100 mg/dL, or 0.10 g/dL). The chronic conditions that are assessed using direct estimates of AAF include acute pancreatitis, chronic pancreatitis, epilepsy, esophageal varices, gastroesophageal hemorrhage, liver cirrhosis unspecified, portal hypertension, and spontaneous abortion. In contrast, the AAF for most of the acute causes of death (e.g., injuries), except for deaths due to motor-vehicle traffic crashes, are based on a meta-analysis by Smith et al. (1999). In this study, the researchers systematically reviewed studies that directly measured the BAC of persons who had died of fatal non-traffic injuries. In this study, injuries were defined as having been alcohol-attributable if the decedent had a blood alcohol concentration (BAC) ≥ 100 mg/dL (0.10 g/dL) at the time of death. The fatal non-traffic injuries that are assessed using direct estimates of AAF from this study include air-space transport, aspiration, child maltreatment, drowning, falls, fires, firearms, hypothermia, motor-vehicle non-traffic crashes, occupational and machine injuries, other road vehicle crashes, poisonings, suicide, and water transport. The AAF for homicide came from a meta-analysis by English et al. (1995) that systematically reviewed studies that measured the alcohol levels of those who caused the crime (i.e., perpetrators) and not just the alcohol level of victims.

Indirectly Measured AAF

For some causes of death, particularly chronic causes, ARDI calculates indirect estimates of AAF. These calculations use pooled risk estimates obtained from large, systematic reviews of the scientific literature, known as meta-analyses, on the relationship between alcohol and various causes as well as data on the prevalence of alcohol consumption at specific levels (e.g., more than one drink per day on average). Most of the pooled risk estimates used in ARDI were drawn from a study done by English et al. (1995) with a few causes of death drawn from other meta- analyses.

Indirect estimates of AAF are calculated in ARDI using the following formula:

(Prevalence)(Relative Risk - 1)
1+(Prevalence)(Relative Risk - 1)
alcohol at a specified level of average daily consumption within a given year, and relative risk is the likelihood of death from a particular cause at a specified level of average daily alcohol consumption. In accordance with the methods used by English et al. (1995), when evaluating the relationship between medium and high alcohol use (see below for definitions) and deaths from various causes, the risk estimates for these consumption levels were divided by the risk estimate for low alcohol consumption, thus making those in the low average daily consumption group the reference population rather than abstainers.


Prevalence Data


When calculating indirect AAF, ARDI uses the prevalence or the proportion of U.S. adults aged 20 years and older (stratified by sex) who reported average daily alcohol consumption at various levels. This information is obtained from Behavioral Risk Factor Surveillance System (BRFSS). The BRFSS data in ARDI are selected based on the same years as both the death data and the life expectancy data used in the application. For example, if the most recent death data were for 2010, then 2010 BRFSS data were used to obtain the prevalence of average daily alcohol consumption.


Calculating Average Daily Alcohol Consumption


The BRFSS currently includes three questions to estimate the prevalence of alcohol consumption in the past 30 days. These questions assess the number of drinking days, the average number of drinks consumed on drinking days, and the number of binge drinking occasions. Binge drinking is defined as consuming 4 or more drinks per occasion for women or 5 or more drinks per occasion for men. Before 2006, BRFSS did not have a sex-specific cutpoint and defined binge drinking as consuming 5 or more drinks on an occasion for everyone.

To better estimate average daily alcohol consumption, the ARDI application uses a procedure called indexing to include self-reported information on binge drinking episodes into the calculation of average daily alcohol consumption. As described in an article by Stahre, et al (2006), there are several steps involved in the indexing procedure, including the following: First, an average daily alcohol consumption is calculated by multiplying the number of drinking days (frequency or F) by the average number of drinks per day (quantity or Q), and then dividing this product by 30. Second, the number of binge drinking days (binge frequency or BF) is subtracted from the total number of drinking days to determine the adjusted frequency (AF) of drinking days (F minus BF, or AF). Third, the adjusted frequency (AF) is then multiplied by the quantity of drinks consumed during drinking days (Q) to calculate drinks consumed on typical drinking days [Q*(AF)]. Next, the number of binge drinking days (BF) is multiplied by the average number of drinks per binge drinking episode (binge quantity or BQ) to obtain the average number of drinks consumed on binge drinking days (BF*BQ). Drinks consumed during typical drinking days [Q*AF)] are then added to the total number of drinks consumed during binge drinking days (BF*BQ) to obtain the total drinks consumed per month [(Q*AF)+(BF*BQ)]. This total is then divided by 30 to yield the indexed average daily alcohol consumption.

To determine the prevalence of alcohol use at excessive consumption levels, the average number of drinks consumed per day (indexed to include binge drinking) is compared to cutpoints specified by the meta-analyses used to obtain risk estimates for a given cause of death. These cutpoints were typically reported as grams of alcohol per day, and then converted into drinks per day, using a 14 gram per drink conversion factor. The causes for which the relative risk estimates were drawn from English et al. (1995) or an updated study by Ridolfo and Stevenson (2001) used the following cutpoints:

Cutpoints used by English et al. and Ridolfo and Stevenson


Cutpoints used by English et al. and Ridolfo and Stevenson
report subheader Alcohol Consumption Level Cutpoints
Average Drinks Per Day
Sex *Low Medium High
Male ≥0.2 ≥2.9 ≥4.3
Female ≥0.2 ≥1.4 ≥2.9

*Excludes those who were abstinent or had < 0.2 drinks/day on average within a 30-day time frame.

The causes for which these cutpoints were applied include breast cancer, cholelithiases, chronic hepatitis, esophageal cancer, hypertension, ischemic heart disease, laryngeal cancer, liver cancer, low birth weight, prematurity, intrauterine growth retardation or death, oropharyngeal cancer, psoriasis, and superventricular cardiac dysrthymia.

For those causes where the relative risk estimates were drawn from meta-analyses by either Corrao et al. (1999) or Bagnardi et al. (2001) the following cutpoints were used:

Cutpoints used by Corrao et al. and Bagnardi et al.


Cutpoints used by Corrao et al. and Bagnardi et al.
report subheader Alcohol Consumption Level Cutpoints
Average Drinks Per Day
Sex *Low Medium High
Male ≥0.1 ≥1.8 ≥3.6
Female ≥0.1 ≥1.8 ≥3.6

*Excludes those who were abstinent or had < 0.1 drinks/day on average within a 30-day time frame.

The causes for which these cutpoints were applied include ischemic stroke, hemorrhagic stroke, and prostate cancer.

Based on these studies, excessive alcohol use was defined in the ARDI application as medium or high average daily alcohol consumption because these consumption levels generally exceeded the average daily consumption levels that are used to define heavy drinking (more than 1 drink/day on average for women; more than 2 drinks/day on average for men).

Data Sources for Total Deaths and Years of Potential Life Lost (YPLL)


Total Deaths Data Set


To calculate alcohol-attributable deaths (AAD), the AAF for a specific condition are multiplied by the number of deaths in a given age category. The death data were obtained from the National Vital Statistics System managed by the National Center for Health Statistics. Deaths were coded using the International Classification of Diseases, Tenth Revision (ICD-10). See Alcohol Related ICD Codes.

The death data were stratified by age and sex using standard 5-year age groupings. In general, ARDI assesses chronic causes of death starting at age 20 and acute causes of death starting at age 15. However, death data were also collected on persons who were younger than 15 years of age at the time of death if they died from alcohol-related causes that specifically affect children. These include fetal alcohol syndrome; fetus and newborn affected by maternal use of alcohol; child maltreatment; and low birth weight, prematurity, and intrauterine growth retardation. Deaths due to motor-vehicle traffic crashes among persons younger than age 15 years were also included in the system, because data on alcohol involvement in these deaths are available through FARS.

Years of Potential Life Lost (YPLL)


YPLL are calculated by multiplying age- and sex- specific average annual estimates of alcohol-attributable deaths due to the 54 conditions included in the ARDI application (e.g., alcoholic cirrhosis of the liver) by age- and sex-specific 5-year average annual estimates of years of life remaining from the National Center for Health Statistics.

Since YPLL is based on the age at death, the YPLL for a particular cause of death are directly related to the age distribution of persons who typically die of that condition. As a result, YPLL generally tends to be higher for causes of death that disproportionately affect youth and young adults (e.g., motor-vehicle traffic deaths) and lower for causes that primarily affect older adults (e.g., ischemic heart disease).

Limitations


ARDI may underestimate the actual number of alcohol-related deaths and YPLL in the U.S. for several reasons. First, BRFSS data on alcohol consumption, which are used to calculate indirect estimates of AAF, are based on self-reports. Among adults, alcohol consumption generally, and excessive drinking in particular, are underreported in surveys because of recall, social desirability, and nonresponse bias (Stockwell et al. 2004). A recent study found that BRFSS identifies only 22% to 32% of presumed alcohol consumption in states based on alcohol sales (Nelson et al., 2010). Second, an increasing proportion of youths and young adults aged 18—34 years use cellular telephones exclusively (Blumberg and Luke, 2010); therefore, landline surveys of persons in this age group might not be representative of this population. Third, BRFSS prevalence estimates are based on alcohol consumption during the past 30 days. As a result, former drinkers, who may have discontinued drinking because of health problems, are not included in the calculation of AAF. Fourth, ARDI does not include estimates of alcohol-attributable deaths for several causes (e.g., tuberculosis, pneumonia, and hepatitis C) for which alcohol is widely believed to be an important risk factor, but where a suitable pooled risk estimate was not available. Fifth, ARDI exclusively uses the underlying cause of death from vital statistics to identify alcohol-related causes of death and does not consider contributing causes of death that may also be alcohol-related. Finally, age-specific estimates of AAF were only available for motor-vehicle traffic deaths even though alcohol involvement is known to vary widely by age, particularly for acute causes, and is generally much greater for deaths involving youth and young adults. This limitation is likely to have resulted in a substantial underestimate of YPLL from deaths due to acute causes.

Scientific Work Group


CDC convened a Scientific Work Group, comprises experts on alcohol and health from academia, government and private sector in 2001 and 2002 to guide the development of the ARDI application.

The Work Group was tasked with selecting all the alcohol-related causes and appropriate alcohol-attributable fractions to be included in the application. In addition, the Work Group had to determine the appropriate data sources to select the relative risk estimates for the calculation of indirectly measured alcohol-attributable fractions. Members of the Work Group provided valuable input into the design and overall functionality of the ARDI application.

References


Bagnardi V, Blangiardo M, La Vecchia C, Corrao, G. A meta-analysis of alcohol drinking and cancer risk. British Journal of Cancer 2001;85(11):1700–05.

Blumberg S, Luke J. Wireless substitution: Early release of estimates from the National Health Interview Survey, January–June 2010 National Center for Health Statistics. Available from http://www.cdc.gov/nchs/data/nhis/earlyrelease/wireless201012.htm. Accessed February 2010.

Corrao G, Bagnardi V, Zambon A, Arico S. Exploring the dose-response relationship between alcohol consumption and the risk of several alcohol-related conditions: a meta-analysis. Addiction 1999;94(10):1551–73.

English DR, Holman CDJ, Milne E, Winter MG, Hulse GK, Codde JP, et al. The Quantification of Drug Caused Morbidity and Mortality in Australia, 1995 edition. Canberra, Australia: Commonwealth Department of Human Services and Health;1995.

Nelson DE, Naimi TS, Brewer RD, Roeber J. U.S. state alcohol sales compared to survey data, 1993–2006. Addiction 2010;105:1589–96.

Ridolfo B, Stevenson, C. The Quantification of Drug-Caused Morbidity and Mortality in Australia, 1998. Drug Statistics Series no. 7. AIHW cat. no. PHE 29. Canberra, Australia: AIHW;2001.

Smith G, Branas C, Miller T. Fatal nontraffic injuries involving alcohol: a meta-analysis. Annals of Emergency Medicine 1999;33(6):659–68.

Stahre M, Naimi T, Brewer R, Holt J. Measuring average alcohol consumption: the impact of including binge drinks in quantity-frequency calculations. Addiction 2006;101:1711–1718.

Stockwell T, Donath S, Cooper-Stanbury M, Chikritzhs T, Catalano P, Mateo C. Under-reporting of alcohol consumption in household surveys: a comparison of quantity-frequency, graduated-frequency and recent recall. Addiction 2004;99:1024–33.

 

 
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