Estimating the Time Trend of Adjusted Incidence of Opioid Dependency and Multiple Factors Related to the Lag Time: Backward Calculation Method

For evidence based decision-making and designing more accurate health system planes for effective prevention on drug dependency, incidence rate and time trend of number of new cases are necessary. This survey was conducted based on data of Kerman drug detoxification agencies in order to determine the time trend of incidence rate of opioid dependency and the effects of various factors on lag time (the time between onset of substance use and first treatment request). In this retrospective cohort study, 4309 opioid users visiting Kerman Welfare Organization between 1997 and 2004 were analyzed. Subgroups were shaped according to the first year of consumption. Estimated incidence of addiction was determined by using backward calculation method. The Effect of various factors on lag time was calculated by multivariable regression method. Relative incidence of addiction between 1997 and 1999 was increased by 70% annually, followed by a slightly decrease to 540 persons in 2000. The minimum estimated number was seen in 2003 (400 cases) and it peaked to the maximum in the next year (1145 cases). The average of lag time was 7.98±6.47 years with median 6 years. The lag time of opium users was 7.81±6.48 and for opium syrup – a liquid prepared from the ashes of smoked opium – users was 8.32±6.17 years (p=0.001). Individuals who have consumed both opium and opium syrup simultaneously, had a more lag (p=0.0001). Men with lag time of 8.1±6.41 years, had a significant longer lag time than women (7.05± 6.78 years).In compare with cases with 20-30 ages (7.86±6.38 years) and cases older than 30 years (7.7±6.44 years), the lag time for persons less than 20 years old (8.62± 6.68 years) was significantly more (p=0.0001). The lag time for illiterates (10.73±7.59 years) was more than cases with academic education (7.87±7.27 years). The lag time for married persons (8.87±6.8 years) was significantly more than singles (4.9±3.76 years). Time trend of addiction can be divided into two parts in recent years. First part is from 1997 to 1999; in this period the number of new cases of addiction increased but from 2000 to 2002 it is fairly constant. Some factors such as being women, younger, more literate, single and simply opium users have a negative correlation with lag time.