after the tuberculosis agent was discovered by robert koch in 1882 , it was hoped that the disease would be controlled and eradicated . unfortunately , more than a century has passed since the discovery and tb still claims lives across the world ( 1 ) . world health organization ( who ) declared tb as urgency in 1993 and urged all nations to control the disease ( 2 ) . in the 21st century , tb poses itself as a major medical concern for all countries . furthermore , with advances in technology , particularly in the biological molecular field and genetic engineering , new horizons have opened in different research areas ( 3 ) . tb is a ne - crotizing chronic or acute disease caused by various strains of mycobacterium , namely , m. bovis and m. africanum , and mostly due to m. tuberculosis ( 4 ) . tuberculosis attacks lungs and involves different body organs and tissues including lymph nodes , pleura , pericardium , kidney and bones ( 5 ) . every 4 seconds one person contract tb and every10 se conds one dies of the disease .- given the current trend and by every decade , almost 300 million people get infected with the tb bacterium worldwide . despite the discovery of the causing agent , vaccine and highly effective medications , the disease still poses a major health challenge globally ( 6 ) . if a person with pulmonary tb and sputum smear positive is not diagnosed and treated in time , he may infect 10 to 15 other people annually . the best way through which one can prevent and control tb is timely diagnosis of smear positive pulmonary tb and effective treatment of the disease ( 7 ) . so far , one third of the world s population has been infected with tb bacillus and 9 million people contract the disease annually . 75% of deaths happen among economically active groups ( 1554 ) ( 8) . in 2009 , tb cases have been reported in all provinces of iran , with most cases seen in sistan and balouchestan , golestan , khorasan razawi , khuzestan , hormozgan , qom , kermanshah and gilan provinces . 80% of the world tuberculosis cases have been reported in 22 countries including pakistan and afghanistan . figures dating back to 40 years ago show that 140 out of 100 thousand people suffered from tb at the time in iran . the patient suffering from drug - resistant tb must be treated for 2 years instead of 6 months . such a patient must be hospitalized , though it is not necessary , and the cost of his medication increased from 4,500,000 irr to 300 million irr . only 50% of the cases survive and the rest die of tb ( 9 ) . the incidence of smear positive pulmonary tb has been declining in iran and each year on average the incidence and the recurrence decreased by 4.1% and 3.6% , respectively . on average , tb mortality rate has decreased by 6.8% and tb case - detection rate has increased by 2.5% annually ( 10 ) . the incidence of tb in iran decreased by 10.1% annually during the first 11 years of assessment ( 19641973 ) ; it increased by 4.3% during the second period from 1977 to 1993 ; the incidence of tb decreased by 4.5% in the third period . during at least the last 10 years , the incidence of tb decreased by 4.5% ( 11 ) . the present study aimed to assess the 10-year trend of tb rate in west azarbaijan province from 2001 to 2010 and to explore some risk factors that affect the trend . this was a time series study conducted on the data recorded in the tb care system within the healthcare system in west azerbaijan province from 2001 to 2010 . the study counted the number of tb cases based on the data recorded by the health care system over the years between 2001 and 2010 . on average , 256 cases of tb were recorded each year , which translates into 2,560 cases over a period of 10 years . to collect the necessary data , a checklist was developed through considering the nature of the study , and studying the recorded data . the questionnaire was design based on the demographic information of the patient files which had 17 simple questions . the questionnaire was given to an epidemiologist and an infectious diseases specialist to control the appropriateness of questions related to tb cases , and after approval , it was used for data collection . the outcome variable was the count of tb and demographic variables were sex , place of residency , pulmonary type , bcg status , employment , education level , age group , and job . the researcher collected all the data of the patients from 2001 to 2010 using the checklist , after coordinating with relevant authorities and obtaining necessary permits from west azerbaijan university of medical sciences . then , all the data were entered into spssv.16 software program . there was not any missing value in the study . a poisson log - linear regression analysis used to explore some factors that might affect the trend of tb rate . all the collected data were entered anonymously in the checklist and the researchers observed the individual s right for confidentiality with regard to the personal details . results of relative risks were adjusted for demographic confounding , which were mentioned above to estimate the relative risk of tb more precisely . probably one of the sources of bias might be overlooking of some tb cases in the western azerbaijan province , although it was not considerable as the expertise of the province claimed it . sampling strategy was a time series and it was considered in the poisson regression analysis by including year of study as a covariate . adjusted and unadjusted results along with 95% ci for relative risks were presented in statistical tables . this was a time series study conducted on the data recorded in the tb care system within the healthcare system in west azerbaijan province from 2001 to 2010 . the study counted the number of tb cases based on the data recorded by the health care system over the years between 2001 and 2010 . on average , 256 cases of tb were recorded each year , which translates into 2,560 cases over a period of 10 years . to collect the necessary data , a checklist was developed through considering the nature of the study , and studying the recorded data . the questionnaire was design based on the demographic information of the patient files which had 17 simple questions . the questionnaire was given to an epidemiologist and an infectious diseases specialist to control the appropriateness of questions related to tb cases , and after approval , it was used for data collection . the outcome variable was the count of tb and demographic variables were sex , place of residency , pulmonary type , bcg status , employment , education level , age group , and job . the researcher collected all the data of the patients from 2001 to 2010 using the checklist , after coordinating with relevant authorities and obtaining necessary permits from west azerbaijan university of medical sciences . a poisson log - linear regression analysis used to explore some factors that might affect the trend of tb rate . all the collected data were entered anonymously in the checklist and the researchers observed the individual s right for confidentiality with regard to the personal details . results of relative risks were adjusted for demographic confounding , which were mentioned above to estimate the relative risk of tb more precisely . probably one of the sources of bias might be overlooking of some tb cases in the western azerbaijan province , although it was not considerable as the expertise of the province claimed it . sampling strategy was a time series and it was considered in the poisson regression analysis by including year of study as a covariate . adjusted and unadjusted results along with 95% ci for relative risks were presented in statistical tables . distribution of demographic characteristics of the study population is shown in table 1 . in our tb study the percentage of male and percentage of female were close to each other ( 52.2% against 47.8% , respectively ) . the percentage of tb cases were living in the urban area of west azerbaijan was 62.4% . also , most of the tb cases were aged between 31 and 65 years old . in terms of education level the highest percentage of tb people ( 75% ) fell in primary school or illiterate group . interesting of the study population was that the frequency of pulmonary tb was higher than the frequency of external pulmonary tb ( 62.6% against 37.4% ) . the coverage of bcg vaccine in the tb population was not remarkable and estimated by 56.4% which is not an acceptable coverage . to understand the trend of tb rate over the years of 2001 and 2010 1 . trend of tb by year in the west azerbaijan , iran distribution of demographic variables of the tb study sample , the west azerbaijan , iran figure 1 shows the overall increasing trend of tb rate over the ten years of our study . fluctuations in the graph suggests that there was a reduction in tb rate for year 2003 then a slightly increase up to 2007 . the important pick of the graph is on year 2008 in which the percentage of tb cases was increase dramatically to 14.5% . however , the trend came back to the same level of percentages belong to the years previous to the year of 2008 . the fluctuation over the years was statistically significant ( chi - square=89.08 ; df=9 ; p < 0.001 ) . to study the effect size of each demographic variable on the mean of the number of tb cases over the followed up years , a poisson log - linear analysis was used and its results were given in table 2 . table 2 shows the regression coefficients ( b ) , standard errors of the coefficients , estimated risk ratio ( rr ) , and 95% confidence interval for rr . all results were adjusted for the size of population of azerbaijan province , as an offset variable , and years of the study . single variable poisson log - linear analysis results for tb count data the most important risk factor was the level of education so that people with primary level or with illiterate level had a statistically significant tb rate of 5.21 ( 4.66 - 5.81 ) times the same rate for people with diploma level or higher degrees adjusted for the years of study . next risk factor was age and as table 2 shows people who aged between 31 and 65 years had 1.85 ( 1.70 - 2.03 ) times rate of tb compare to the reference group , significantly . the next two risk factor were type of tb and place of residency , i.e. , pulmonary tb cases had higher rate than external pulmonary tb cases ( rr=1.67 ; ( 1.54 - 1.80 ) ) and rate of tb in urban area was 1.66 ( 1.54 - 1.80 ) times more than the rate of rural area . in terms of gender , rate of tb in male cases was 1.09 ( 1.01 - 1.19 ) times the rate of tb in females and statistically significant . finally , the last factor with the lowest risk was bcg with rr=1.29 ( 1.20 - 1.40 ) for people who received bcg compared to the people who had not received it . this is probably a significant result by chance and should be tested in a multiple analysis to see if bcg still has a significant effect as the above after adjustment for the other factors . as some risk factors may modify the size effects of the other factors we used a multiple poisson log - linear analysis to estimate the adjusted effects of each factor on the rate of tb for the years of study , population offset , and for the other factors in the log - linear model . the interesting result of the multiple analysis was that although the bcg factor had a significant rate of rr=1.29 in the single variable analysis , it was not a protective significant factor in the multiple variable analysis , i.e. rr= 1.07 ( 0.98 - 1.16 ) . it was in accordance with the coverage percentage of bcg which was very low in the tb population ( 56.4% ) as mentioned in the descriptive results . all the remaining factors had significant effects on the trend of tb even after adjustment for year and population size . among them education level and being housewife had higher rr , i.e. rr= 1.86 ( 1.63 - 2.10 ) and rr = 1.61 ( 1.39 - 1.86 ) , respectively ( table 3 ) . multiple poisson log - linear analysis results for tb study sample , west azerbaijan , iran to justify the log - linear results for the tb trend in the data of azerbaijan province in iran , the good - ness - of - fit statistics of the log - linear model used in our study was checked and as likelihood ratio and pearson statistics in table 4 show the model was accepted in terms of assumptions of linearity , poisson distribution for tb count data , and stability of variance ( p= 1.000 ) . it is important to note that in the log - linear model only main effects of the factors were included in the analysis , i.e. , the model was not a saturated one . a key factor in health planning in any society is to determine the incidence trend of diseases . knowing the pattern of changes in the incidence of diseases in a country can be of high significance for countrywide planning strategies . public health organizations believe that assessing or monitoring the incidence trend of diseases , mortality rate and social , behavioral and health risk factors may contribute to unfavorable health incidents . studying the trend of changes in prevalence or incidence rates provides valuable information for needs assessment , design and revision of programs and development indices in a country . assessing the data over a period can also help predict the frequency of future incidents . the present study investigated the tb incidence in 10 years and its incidence in west azerbaijan province in 5 years . the findings of this survey suggest that only 3.8% of the patients were hiv positive . aids has been the most common factor in spreading tb as it weakens the body s immune system . a rise by two to three times in hiv cases was documented for the incidence of tb in the 1990s ( 12 ) . the comorbidity of hiv and myco - bacterium tuberculosis increased the risk of active tb by 5 to 10% annually ( 20 to 37 times the number of non - hiv positive people ) . the figure is 5 to 10% for non - hiv positive people in their lifetimes ( 2 ) . in countries where the prevalence of hiv is more than 1% , the rate of tb is higher among women than among men ( 13 ) . the effects of aids virus on tb are as follows : low rate of treatment , high morbidity , recurrence and non - adherence to treatment due to side - effects of drugs , death during the treatment , and rise in the possibility of transmission of drug - resistant species ( 11 ) . the present research showed that the total number of recorded tb cases within 10 years ( 20012010 ) was 2,560 . most cases occurred in 2008 when 370 people contracted the disease while the least number of cases was reported in 2005 when 184 people contracted it . the number of recorded cases in the first year ( 2001 ) was 215 people while it increased to 298 in the last year , that is , 2010 . an assessment of the incidence rates showed that it was 8.70% per 100,000 people in 2006 . this comes as the rate reached 9.91% in 100,000 in 2010 with a rising trend in the incidence of the disease . they assessed 1,323 cases recorded in the tb healthcare system of the province between 2004 and 2009 . in the period , the rate of smear positive during the period was within the acceptable range of iran s program to control tb . however , the incidence of extrapulmonary tb was higher than the acceptable index ( 14 ) . . showed in isfahan that the rate of case - detection was 90% and 77% , the rate of successful treatment was 80% and 58% and the incidence rate of smear positive pulmonary tb was 2.28% and 1.11% , respectively for 2005 and 2006 . the reason why they went for a 5-year period was that they had no access to accurate population data over a period of 10 years . this is a main drawback to the program and a weakness of the healthcare system in that statistics are not stored and sorted out properly , which by itself led to a disruption in appropriate application of the statistical methods and better reasoning . however , the nature of this study has made it difficult to accurately determine the cause of the changes in the trend of the disease . assessing tb in terms of gender thus , most of the recorded tb patients were men . however , a study on the trend of smear positive pulmonary tb between 2001 and 2008 showed the west azerbaijan province was witnessing a decreasing trend of tb incidence ( 10 ) . the rate was 9.11 per 100,000 people among men in 2005 and 8.27 per 100,000 people among women in 2010 . the rate also increased from 8.27 per 100,000 among women in 2006 to 10.73 per 100,000 in 2010 . the results of our study show that despite the low percentage of female tb cases , the high number of women contracting the disease in 2006 compared to men shows how vulnerable they are to tuberculosis . it seems that the number of female cases of tb is obviously rising in comparison to men . the findings of our study also showed that the mean age of the recorded patients was 49.6920.68 . overall , the mean age of men was higher and most reported cases were higher than 60 years old . given the rise in the age of tb patients in iran , it seems that one of the features of tuberculosis in developing countries is evident among the population under study . a study conducted in the us between 1994 and 2007 showed that of 18,965 reported cases , 31% were adolescents under 18 . the research found that more than 40% of decrease came about among adolescents ( 16 ) . tb is mainly found in industrial nations among the elderly and it is often caused by the recurrence of old infections . that is due to the weakness of the immunity system , as a result of age . in those countries , although most cases were recorded in urban areas ( see the results of a study in damghan ) ( 17 ) , the incidence rate among urban people decreased from 9.97 in 100 thousand in 2006 to 8.99 in 100 thousand in 2010 . the rate increased among rural people from 6.79 in 100 thousand in 2006 to 11.33 in 100 thousand in 2010 . however , a study showed a higher recovery success rate in the treatment for positive smear lung tb among rural patients as compared to urban patients in the province ( 14 ) . a comparison of results showed that the incidence rate of the disease was higher among rural people . different studies show that the incidence rate of tb among urban people is more than rural people ( 1 ) . a study showed , the results of puissan regression aimed at determining the concurrent effects of such factors as gender , age and place of living were significant only for age and place of living . given the fact that tb is a disease of poverty , economic shortages and lack of knowledge , the decreasing trend of the disease is indicative of a rise in people s awareness about tb and an increase in income and living standards of people . the rise in the arte also stems from social and political changes in the country and in neighboring nations ( 20 ) . it was impossible for us to conduct 10-year calculations that would involve all necessary variables . this was due to lack of access to separate population statistics , which was a major restriction faced by our study . another drawback was that the data recorded with the healthcare deputy office were possibly incomplete . hence , any deficiencies or changes in the system can change the results and cause problems over which the researchers have no control . conside - ring the results of the present study , we can improve the status quo by taking the following measures : most tb patients are poor and may be addicts ; there is no way to get them to follow the right medical regimen . for the reason , we need to make appropriate measures to help them earn a living so that they can afford the expenses of dots treatment . we must prevent test treatments practiced in some parts of iran and authorities must deal with violators appropriately . decisions should be made and directives should be issued as to listing some diseases as a threat to public health and making the treatment of patients particularly tb patients mandatory so that they can not escape treatment . proper knowledge of epidemiological differences and critical parts of towns ; case - detection interventions among vulnerable people , particularly more susceptible age groups ; studying the implementation of tb case - detection programs at healthcare centers ; standardizing sputum microbiology labs and using them optimally ; properly communicating with private healthcare centers ; strengthening infrastructures ; educating the population ; empowering the personnel involved in controlling the disease , and following up on people in contact with the patients are all a necessity . we need to take more effective and comprehensive measures to achieve the goals of the millennium , that is , identifying at least 70% of expected positive smear tb cases , reducing the incidence and mortality rate among tb patients to 50% by 2015 as compared to 1990 and finally eradicating the disease by 2050 ( decreasing the number of tb cases to less than 1 person in a million ) . ethical issues ( including plagiarism , informed consent , misconduct , data fabrication and/or falsification , double publication and/or submission , redundancy , etc . ) have been completely observed by the authors .