Ethics approval was obtained from the University of British Columbia, Behavioural Research Ethics Board (H06-04043). Mortality and hospital data were received from BC Vital Statistics and BC Ministry of Health (respectively) by age group, sex, health authority, health services delivery area (mortality only), and year.  All data are securely held at BC Centre for Disease Control. The underlying cause of death code (UCOD) and the most responsible diagnosis code (MRD) were used in the computation of alcohol, tobacco, and illicit drug attributable mortality and morbidity respectively. All rates were standardized by age and sex using the 2001 BC population as the standard population.

Computing Alcohol-Attributable Fractions

AFs for chronic diseases are calculated by using the formula:

AF= [Σ^k_i=1 P_i(RR_i–1)]/ Σ^k_i=0 P_i(RR_i–1) + 1]

Where:           

k: total levels of exposure

i: exposure category with baseline exposure or no exposure i=0

RR(i): relative risk at exposure level i compared to no consumption

P(i): prevalence of the i^th category of exposure

Relative risk estimates were obtained from a meta-analysis of previous literature. Four levels of alcohol consumption were used: abstainer, low, hazard, and harmful. This corresponds to 2.5 grams of ethanol or less, 2.6-40, 41-60, and 61 or more grams of ethanol per day for men and 2.5 or less, 2.6-20, 21-40, and 41 or more grams per day for women. (One glass of beer or wine is equivalent to 15 grams of ethanol). Prevalence data were obtained from recent provincial and national surveys. For injuries attributable to alcohol, AFs were based on direct estimates of alcohol involvement from the published literature.

Alcohol AFs were then adjusted using BC consumption data. BC per capita consumption was taken from the alcohol consumption component of the BC AOD monitoring project. The data from this component, however, does not reflect unrecorded alcohol consumption. A further 10% was added to the BC per capita consumption data to account for unrecorded alcohol consumption. New alcohol AFs were then estimated using the following formula:

AF_ref = population aetiologic fraction for reference year

F = change factor in per capita consumption from reference year to year of interest

PCC _ref = per capita consumption for reference year (eg. Rehm et al. used 9.77 for 2002)

PCC _x = per capita consumption for year of interest

Computing Tobacco-Attributable Fractions

AFs were calculated using the formula above. Relative risk estimates and prevalence data were obtained from a meta-analysis of previous literature and recent provincial and national surveys respectively.

Computing Illicit Drug-Attributable Fractions

For diseases that exist completely because of drug use, the AF is by definition 100%. For suicides, we took the number of suicides with illicit drugs as a contributing factor divided by the total number of suicides. For hepatitis C virus (HCV) and HIV, we used estimates from literature of the proportions of HCV- and HIV-positive individuals who are injection drug users. For low birth weight due to maternal opiate consumption, we used the formula above. For hepatitis B virus (HBV) and endocarditis, we used the AF from literature. For homicide and motor vehicle accidents (MVA), we used estimates of cannabis- and cocaine-caused MVA and homicides from literature.

AFs were then multiplied with overall mortality and hospitalization numbers to obtain the total burden of disease from alcohol, illicit drugs and tobacco by age, sex, and health authority.

For detailed prevalence and relative risk estimates, please see The Cost of Substance Abuse in Canada 2002 (Rehm J. et al. 2006).

This project uses the same ICD 10 tables for alcohol, tobacco and illicit drugs that were used in Jurgen Rehm’s project.

Permission to share these results was obtained from the BC Ministry of Health Data Steward and the BC Provincial Health Officer.