New opiate and crack-cocaine users: characteristics and trends 24 
 
Table 12: Estimated 20-year lag-to-treatment distribution for model one 
 
The cumulative percentages from the table above can then be combined with statistics showing 
actual numbers of first presentations to treatment by year of onset to calculate an incidence 
trend, as demonstrated in Table 13. 
Table 13: Table showing the data used to estimate incidence in model one and the results21 
  
Year of 1st treatment         
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Total 
Percentag
e of total 
incidence 
accounted 
for by 
observed 
Estimated 
number yet 
to come to 
treatment 
Estimated 
total 
incidence 
Year 
1st 
use 
2005 1,305  1,508  1,533  1,250  938   800  512  408  376  330  8,960  85%        1,523         10,483  
2006 - 1,297  1,727  1,624  1,116  821  611  471  470  358  8,495  82%        1,824         10,319  
2007 - - 1,482  1,906  1,532  1,020  671  566  491  416  8,084  79%        2,183         10,268  
2008 - - - 1,446  1,857  1,456  840   659  570  424  7,252  75%        2,437           9,689  
2009 - -  - - 1,580  1,811  1,018  727  627  527  6,290  70%        2,701           8,990  
2010 - - - - - 1,404  1,101  933  757   544  4,739  62%        2,864           7,602  
2011 - -  - - -  - 1,001  1,109  988  646  3,744  53%        3,269           7,013  
2012 - -  - -  -  -  -  967  1,149  920  3,036  41%        4,287           7,324  
2013 - - - - -  -   -  - 1,021  1,204  2,225  27%        6,065           8,290  
2014 - - - - -  -  -  -  - 869  869  12%         
Total   1,305 2,805 4,742 6,226 7,023 7,312 5,754 5,840 6,449 6236.4 53,693        
 
Reading down the year columns, the table shows that of the 6,449 people who presented for 
opiate/crack treatment for the first time in 2013, 376 said they had begun using in 2005. Another 
470 said they started using in 2006, and so on.  
Reading across the table shows that of all those who said they began using opiates/crack in 
2005 (8,960), 1,305 also presented to treatment for the first time in that year (which is 15 per 
cent of the observed cohort from Table 11 and 12 per cent of our estimated total cohort from 
Table 12). Another 1,508 presented for the first time a year later, and so on. The first number in 
the totals column (8,960) therefore represents all individuals who said they began using in 2005. 
It is therefore the ‘observed’ incidence level. The column to the right of this is the cumulative 
percentages from the estimated lag-to-treatment distribution in Table 12. This shows the 
                                                                                                                                                                                                                 
otherwise similar data (i.e. first treatment presentation and year of initiation) from OCUs attending treatment in the 
Manchester area.   
21  Note that the data for 2014 only includes Jan–Oct as this was all that was available. Hence we do not do not attempt to 
calculate an incidence estimate for 2014 and we adjust all the values in that column by multiplying by (12/10) to account for 
the missing months.