  with the rapid economic development , elevated standard of living , dietary shifts , lifestyle alterations , and aging , diabetes mellitus ( dm ) has become an important public health problem worldwide [ 13 ] , which is estimated to be the third most challenging disease threatening public health after malignant tumors and cardiocerebral vascular diseases .
it has been estimated that the global number of individuals with diabetes will double from 171 million in 2000 to 366 million in 2030 among adults aged 20 years .
data from european countries have indicated that the health care expenditure for patients with diabetes mellitus was significantly higher than for those who were not diagnosed with this disease [ 68 ] .
also , in the united states , it has been estimated that approximately 17.5 million people were diagnosed with insulin - dependent diabetes mellitus ( iddm ) or non - insulin - dependent diabetes mellitus ( niddm ) in 2007 , and the total annual cost in higher medical costs and lost productivity was estimated to be $ 174.4 billion , including $ 159.5 billion for the 16.5 million people with niddm and $ 14.9 billion for the 1 million people with iddm .   
a recent global study indicated that the prevalence of diabetes mellitus was rising rapidly , particularly in developing countries .
moreover , more than 60% of the population with diabetes mellitus all worldwide comes from asia , as this remains the world 's most populous region .
the number of persons living with diabetes will increase substantially in each asian country over the next few decades .
china is the world 's largest developing economy and the most populous country , with one - fifth of the global population . due to the rapid westernization of diet and lifestyle ,
the total number of people with diabetes in china is projected to increase from 20.8 million in 2000 to 42.3 million in 2030 .
diabetes and its complications also result in significant economic burden among individuals , families , and health care systems . according to who estimates
, china will lose $ 558 billion of its national income to heart disease , stroke , and diabetes from 2006 to 2015 .
therefore , there is an urgent need to reduce the future diabetes burden by providing adequate financial resources and structures of health care delivery in china , particularly within the context of continued rapid urbanization .  
diabetes can affect many organ systems throughout the body ( e.g. , nervous system , renal system , and eyes ) and can lead to serious complications over time [ 14 , 15 ] .
recently , a meta - analysis confirmed that individuals with diabetes mellitus have an approximately 2-fold higher risk of large - vessel disease , such as coronary heart disease ( chd ) and stroke , and nonvascular mortality .
thus , control of the growing prevalence of diabetes mellitus has been widely promoted in order to reduce the risk of large - vessel disease .
the pharmacological treatment of diabetes mellitus   and lifestyle modification   have been shown to decrease the incidence of diabetes mellitus .
however , it is very important to first determine the prevalence of diabetes mellitus in the general population , the levels of awareness , treatment , and control of diabetes mellitus .
the key elements of effective control include an improvement in the awareness of diabetes mellitus among both health professionals and the general population .
some studies [ 2123 ] have revealed that more than half of the individuals with diabetes mellitus were unaware of the condition .
furthermore , the percentage of patients with diabetes mellitus who were treated and controlled to target levels was substantially low . moreover , knowing factors associated with the conditions should be useful for health services and public health action in terms of management and prevention .
an improvement in the awareness , treatment , and control of diabetes is , therefore , essential for the management and reduction of its prevalence .   
recently , a systematic review on the prevalence of diabetes was published which included 22 cross - sectional studies .
however , there was no information provided about the trends in the prevalence of diabetes and the awareness , treatment , and control of the disease .
to date , there has been no systematic review or meta - analysis on the level of awareness , treatment , and control of diabetes in mainland china .
thus , the purpose of the current paper was to perform a systematic review and meta - analysis of the published literature regarding the prevalence , awareness , treatment , and control of diabetes in mainland china .
the objectives of our study were ( i ) to estimate the trends in prevalence , awareness , treatment , and control of diabetes from 1979 to 2012 in mainland china ; and ( ii ) to estimate the gender , location , and age distributions of patients with diabetes .
this systematic review and meta - analysis could provide an overview of the epidemiology of diabetes in the past thirty years in china on the level above the provincial .
  pubmed , embase , chinese biomedical database ( cbm ) , cnki database , chinese wanfang database , and chongqing vip database were searched from the date of establishment up to february 2013 using the search terms  chronic disease ,   metabolic syndrome ,   diabetes ,   diabetes  mellitus , 
 prevalence ,   epidemiology ,   awareness ,   treatment ,   control ,   cross - sectional survey ,   longitudinal study  and  china  .
all included studies were required to meet the following selection criteria : ( i ) cross - sectional or longitudinal studies that provided the prevalence , awareness , treatment , and control of diabetes in mainland china ; ( ii ) based on population samples rather than volunteers ; and ( iii ) the study population being representative of the provincial or national population .
exclusion criteria were ( 1 ) reviews , editorials , letters , commentaries , or reports ; ( 2 ) articles repeating data from other articles that were already included ; ( 3 ) self - reporting data ; and ( 4 ) studies based on special populations , that is , physical examination crowds , industry , or occupational groups , ethnicity , or age groups .
we contacted the authors of eligible studies to request further or missing information if needed for subsequent analysis .
data regarding the first author , year of publication , study location , survey date , age range , sampling method , location ( urban / rural ) , diagnostic criteria , diagnosis method , total sample size , total case size , gender distribution , age distribution , and prevalence , awareness , treatment , and control of the diabetes were extracted wherever available .
an awareness of dm was considered a self - reported previous diagnosis of dm by a physician or other healthcare practitioner among participants with dm .
treatment of dm was determined as self - reported if taking oral hypoglycemic medications , using insulin , or other nonpharmacological treatments for the management of high glucose levels .
the management of fasting plasma glucose ( fpg ) at levels lower than 7.0  rnmol / l ( 126  mg / dl ) in patients of dm in treatment was defined as control of dm .
stata software version 11.1 ( stata , college station , tx , usa ) and review manager ( revman ) version 5.1   were used to calculate the pooled prevalence , awareness , treatment , and control of diabetes from all of the eligible studies .
a summary of the prevalence , awareness , treatment , and control estimates was obtained using random - effects meta - analysis .
we identified 45,947 references through electronic searches of pubmed ( n = 3,541 ) , embase ( n = 4,013 ) , chinese biomedical database ( cbm ) ( n = 9,547 ) , china national infrastructure database ( cnki ) ( n = 8,189 ) , chinese wanfang database ( n = 9,165 ) , and chongqing vip database
after excluding duplicates and following examination of titles , abstracts , and full texts , 172 potentially eligible studies were identified .
in addition , with a manual search of references , two more studies [ 27 , 28 ] were obtained from the papers .
57 included repetitive data , 54 studies were researched in specific populations , and 7 studies were self - reports of diabetes prevalence .
therefore , we obtained 56 studies in total that were suitable for inclusion in our study [ 2123 , 2779 ] . among the included studies , one study   contained survey data for two periods , with the data for 2002 - 2003 being duplicated in another study .
we summarized the characteristics of the 56 included studies which contained 7 nationwide studies and 49 provincial studies conducted in the general chinese population . among the included studies ,
there were 56 concerning the prevalence of diabetes , 10 regarding the awareness of diabetes , 8 involving the treatment of diabetes , and 8 regarding the control of diabetes .
a total population of 2,058,243 individuals was investigated , and 120,992 patients with diabetes were detected .
the 56 studies were conducted among all of the provinces of mainland china , and included 22 provinces , 4 municipalities , and 5 autonomous regions .
four studies were conducted among all ages , with the age of participants in 9 studies being greater than 30 years old ; 3 studies did not provide information regarding the age range investigated .
the sampling methods applied in the studies included random sampling , stratified sampling , cluster sampling , multistage - stratified sampling , or combinations of these and general surveys . in terms of diagnostic criteria for diabetes ,
7 studies used the american diabetes association criteria ( ada ) from 1997 or 2009 , 31 studies used the criteria of the world health organization ( who ) from 1985 , 1988 , 1995 , or 1999 , one study used the international diabetes federation criteria ( idf ) from 2005 , and one study was performed according to the criteria outlined in the lanzhou conference on diabetes in china ; however , 12 studies did not provide clear information on the diagnostic criteria employed .
eighteen studies used fasting plasma glucose ( fpg ) and oral glucose tolerance tests ( ogtt ) as the methods of diagnosis , 17 studies used fpg alone , 13 studies used ogtt , and one study used fpg , ogtt , and urine glucose tests . the prevalence of diabetes in 56 studies varied from 0.61% to 20.85% .
levels of awareness , treatment , and control ranged from 28.50 to 62.54% , 17.72 to 92.50% , and 6.86 to 35.87% , respectively ( table 1 ) .
as shown in table 2 , the overall prevalence of diabetes was 6.41% ( 95%ci : 5.507.33 ) .
table 2 and figure 1(a ) illustrate the trend in the overall prevalence of diabetes in mainland china from 1979 to 2012 , showing that it increased as time progressed .
the lowest prevalence of 0.81% was found in 1979 initially and showed a stable increase until 2001 . after a slight decrease
, the prevalence increased quickly from 2002 to 2009 ( with the highest prevalence of 15.60% in 2009 ) , before decreasing rapidly again from 2009 to 2012 .
the prevalence of diabetes in males was 6.91% ( 95%ci = 5.728.09 ) , and the prevalence in females was 6.43% ( 95%ci = 5.127.74 ) ; there was no significant difference in the prevalence of diabetes between males and females ( or = 1.07 , 95%ci = 0.981.16 ) .
overall , trends in the prevalence of diabetes between males and females were increased and similar to the overall trend for the prevalence of diabetes ; no significant differences could be observed between males and females ( figure 1(b ) ) .  
the prevalence of diabetes in urban and rural areas was 7.82% ( 95%ci = 5.939.72 ) and 6.26% ( 95%ci = 4.258.27 ) , respectively .
a statistically significant difference could be found in the prevalence of diabetes between urban and rural areas ( or = 1.61 , 95%ci = 1.252.06 ) . as shown in figure 1(c ) , trends in the prevalence of diabetes in both urban and rural areas increased over time , and the prevalence of diabetes in urban areas was consistently higher than that in rural areas .  
the prevalence of diabetes in the groups aged less than 39 , 4059 , and over 60 was 1.98% , 6.96% , and 13.24% , respectively .
table 2 and figure 1(d ) show the information and trends in the prevalence of diabetes by age .
an increasing tendency could be observed in all age groups over time . also , the prevalence of diabetes increased with age ( figure 1(d ) ) .   
however , no obvious increasing trend could be observed in awareness of diabetes from 1998 to 2012 ( figure 2(a ) ) .
overall , the rate of awareness of diabetes in males was 40.86% and was 41.58% for females .
no significant difference could be found in the awareness of diabetes between males and females ( or = 0.99 , 95%ci = 0.871.13 ) ( table 3 ) .  
the awareness rate in urban areas was 44.25% ( 95%ci = 32.655.9 ) , while it was 34.27% ( 95%ci = 2147.54 ) in rural locations ( table 3 ) .
the combined result for the treatment rate of diabetes was 42.54% ( 95%ci = 13.6971.38 ) ( table 3 ) .
as shown in figure 2(b ) , an increasing tendency in the treatment of diabetes could be observed from 2001 to 2005 .
however , it decreased quickly after 2008 and then rapidly increased again from 2010 to 2011 .  
the treatment rate of diabetes in males was 38.48% , whereas it was 41.18% for females . comparing the treatment rate of diabetes for males to that of females ,
no significant difference could be observed ( or = 0.9 , 95%ci = 0.721.14 ) ( table 3 ) .  
the treatment rates in urban and rural areas were 50.18% ( 95%ci = 31.22100.39% ) and 45.42% ( 95%ci = 12.7% and 103.6% ) , respectively ( table 3 ) . comparing the treatment rate of diabetes between rural and urban areas
, there was no significant difference ( or = 1.30 , 95%ci = 0.772.20 ) .  
the pooled control rate was 20.87% ( 95%ci = 10.7630.97 ) for diabetes from the combined information of eight studies ( table 3 ) .
there was an increasing tendency in the control of diabetes from 2001 to 2008 , whereas the trend of control from 2008 to 2011 was similar to that of the treatment ( figure 2(b ) ) .  
overall , the control rate of diabetes in males was 19.26% and was 19.03% for females .
there was no significant difference between males and females ( or = 1.06 , 95%ci = 0.981.15 ) ( table 3 ) .  
the control rate of diabetes in urban areas was 16.7% ( 95%ci = 2.3935.8% ) and 18.59% ( 95%ci = 1.238.39 ) in rural locations .
no significant differences were found between urban and rural populations ( or = 18.59 , 95%ci = 1.2038.39 ) ( table 3 ) .
due to the rapid development of the economy in china , the dietary habits and lifestyles of individuals have changed remarkably , which might have contributed to the increase in many chronic diseases such as diabetes [ 11 , 80 ] .
overall , the results of our study showed that the prevalence , awareness , treatment , and control of diabetes in mainland china were 6.41% , 45.81% , 42.54% , and 20.87% , respectively .
a higher prevalence of diabetes was found in urban areas than in rural locations . as for the awareness of diabetes , this was also higher among residents in urban than in rural areas .
there were no significant differences when data were stratified by gender or location in the subgroup analysis with regard to the treatment and control of diabetes .
to the best of our knowledge , our study is the first systematic review on the awareness , treatment , and control of the diabetes and covers the longest time period from 1979 to 2012 in mainland china on the level of survey above the provincial .
the diabetes prevalence in our study ranged from 0.61%   to 20.85%   with an average of 6.41% ; however , many authors have shown different findings when studying other countries in asia .
similar to our results , it was reported that the prevalence of diabetes in indonesia is 5.7% .
in contrast , a survey conducted in vietnam indicated a prevalence of 1.4% to 2.5% , which is relatively lower than that of our study . on the contrary , epidemiological data from thailand and japan show that diabetes prevalence estimates were approximately 11.9% and 10% , which were higher than our study [ 82 , 83 ] .
the wide variation in the prevalence could be explained by the heterogeneity of the studies , geographical differences , and the application of different diagnostic and sampling methods . according to the statistics of the idf
, nationwide epidemiological surveys of diabetes were conducted in china and the prevalence showed a 5-fold increase [ 27 , 32 , 8587 ] . in accordance with this , an increasing trend in the prevalence of diabetes was found in our study .
however , limited studies were included for pooled prevalence estimates ; therefore , more studies with high quality and larger sample sizes are required to further confirm our findings .   as to the prevalence by gender , no significant difference could be found in our study between males and females , which is similar to the results of most studies according to the international diabetes federation ( idf ) . however , the study reported by yang et al . in 2010   showed a difference in the prevalence of diabetes between males and females .
this might partly be explained by the fact that men are more accustomed to unhealthy diets due to their work and also smoke more frequently than women , which are the main risk factors for diabetes .
moreover , men are much more careless with regard to their health . however , further studies are required to confirm our findings .    in the analysis stratified by location , the prevalence of diabetes in urban areas was higher than in rural locations , with an odds ratio of 1.61 for residents in urban and rural areas , which suggests that residents in urban areas were more likely to suffer from diabetes than those in rural regions . in accordance with our findings ,
many studies worldwide have also reported a higher prevalence of diabetes in urban areas than in rural populations [ 32 , 86 , 88 ] . with the rapid development of the economy
urbanization is related to the change in the food supply and lifestyles which could lead to an unhealthy diet , sedentary habits , and overnutrition [ 72 , 90 ] .
the prevalence of overweight and obesity has increased over the past two decades , especially in urban areas and high - income groups , which are the risk factors for diet - related disease and contribute to the development of diabetes .  
it was reported that the prevalence of diabetes increased with age [ 85 , 86 ] .
a nationwide epidemiology survey showed that prevalence of diabetes in the age group of 2039 was 1.01% , while it reached 6.31% in the age group over 40 ; however , the highest prevalence of 11.34% could be found in the age group over 60 .
results of our study further confirm these findings . with the largest population in the world
, china has become an ageing country ; therefore , the prevalence of diabetes will increase as a result of the aging population in china .
ten studies provided information on the awareness of diabetes . among the included study subjects , 45.81% were aware of having diabetes . from 1998 to 2011 , there was no obvious improvement in the awareness rate of diabetes .
however , we report a difference between the urban and rural areas when conducting stratified analysis by location .
this difference in awareness may be a result of a lack of access to health care and knowledge in rural areas .
increasing the awareness through health education remains an effective method for the prevention and treatment of diabetes .    among the participants who had diabetes in our study , 42.54% of them were undergoing treatment
this is high compared with the study which first reported the treatment rate of diabetes ( 27.2% ) in china .
the results of our study also showed an increasing trend in the treatment rate of diabetes from 2001 to 2011 .
convenient , economic , and effective detection tools could improve the treatment rate of this disease .  
it was reported that controlling blood glucose at a normal level can prevent many diabetes - related complications , such as retinopathy , nephropathy , neuropathy , and macroangiopathy .
the control rate of diabetes in our study is 20.87% , which is higher than that reported from a previous study with a control rate of 9.7% , but lower than that identified in another study ( 40.3% ) .
the control of diabetes can be influenced by many factors , for example , obesity , smoking , insufficient exercise , and genetic susceptibility .
moreover , adjusting dietary habits , changing lifestyles , and giving up smoking are essential when taking the risk factors for diabetes into account .   
coory   stated that it was very difficult to avoid heterogeneity in a meta - analysis , and this is also true for the meta - analysis of data from epidemiologic studies due to methodological problems .
there were several methodological problems that might help to explain the heterogeneity : ( 1 ) different degrees of urbanization and socioeconomic conditions existed ; ( 2 ) the included studies were carried out in different cities at various time points ; ( 3 ) large differences existed in the age range , sampling methods , sample sizes , and response rates ; ( 4 ) different diagnostic criteria and diagnosis methods were used in studies , with other studies not mentioning them at all ; and ( 5 ) not all of the included studies provided sufficient information on gender , location , and age for subgroup analysis
.   there are some limitations of the current study which need to be highlighted .
firstly , the present study might have underestimated the true prevalence of diabetes , since some of the studies included in the present review only used fasting plasma glucose ( fpg ) levels to diagnose new cases of diabetes ; also , some studies did not provide any information about the diagnostic methods .
thus , more accurate measurements in the detection of undiagnosed diabetes are necessary in future research , for example , the two - hour glucose tolerance test and the oral glucose tolerance test ( ogtt ) .
secondly , in addition to the subgroups of gender , location , and age , we did not report any positive risk factors associated with the prevalence of diabetes and the awareness , treatment , and control of the diabetes ( e.g. , overweight , obesity , hypertension , and hyperlipidemia ) ; thus , we were unable to assess the association between them .
the age distribution in the sample population could markedly affect the results , since some locations contain a large number of individuals > 40 years old ; therefore , the prevalence of diabetes in some studies is likely to be higher than in others .
fourthly , limited studies were included in our meta - analysis for the pooled estimates ; for example , only one study was included for analysis in 2009 and 2012 as studies from that time are possibly yet to be published .
this could also be seen with regard to the trends in awareness of diabetes in 2001 and in the treatment and control of diabetes in 2011 .
a further limitation of the present study is that information in the subgroup analysis of awareness , control , and treatment by gender , location , and age was limited ; therefore , we did not perform the relevant trend analyses .
the study showed an increasing trend for the prevalence , treatment , and control of diabetes among the population of mainland china from 1979 to 2012 , but not in the awareness .
this review will help us understand the gaps in the current research , which is useful for investigators and health care providers regarding aboriginal health .
thus , urgent measures are needed to prevent the high prevalence of diabetes and to improve diabetes awareness , control , and treatment among the chinese populations .
 diabetes mellitus ( dm ) is one of the primary causes of premature death and disability worldwide . 
 we performed a systematic review and meta - analysis of the published literature regarding the trends in prevalence , awareness , treatment , and control of diabetes mellitus in mainland china . 
 pubmed , embase , chinese biomedical database , china national infrastructure database , chinese wan fang database , and chongqing vip database were searched . 
 fifty - six eligible studies were included . 
 increasing trends in the prevalence , treatment , and control of diabetes in mainland china from 1979 to 2012 were observed . 
 the pooled prevalence , awareness , treatment , and control of diabetes mellitus were 6.41% , 45.81% , 42.54% , and 20.87% , respectively . a higher prevalence of diabetes mellitus was found in urban ( 7.48% , 95%ci = 5.45~9.50 ) than rural ( 6.53% , 95%ci = 4.30~8.76 ) areas . 
 furthermore , an increasing chronological tendency was shown in different subgroups of age with regard to the prevalence of diabetes . 
 a higher awareness of dm was found in urban ( 44.25% , 95%ci = 32.60~55.90 ) than rural ( 34.27% , 95%ci = 21.00~47.54 ) populations , and no significant differences were found in the treatment , and control of diabetes among the subgroups stratified by gender and location . from 1979 to 2012 , the prevalence , treatment , and control of diabetes mellitus increased ; nevertheless , there was no obvious improvement in the awareness of diabetes . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion