around the world , populations have changed rural areas for cities , becoming more sedentary and consuming great amounts of industrialized foods and beverages , which have contributed for the increase of obesity and chronic diseases , such as cancer . these changes began in europe , north america , and other countries that became industrialized in xix century . in recent decades , there was acceleration in urbanization process around the world , especially in low - middle - income countries , like brazil . patterns of physical activity , body composition , and breastfeeding are determined by environmental ( urbanization , urban planning , which includes transport systems ) , economic ( social status ) , and social ( education level ) factors , influencing , thus , the occurrence of several types of cancer [ 1 , 2 ] . breast cancer is the most common cancer in women worldwide and has been associated with higher socioeconomic status and urbanized populations [ 2 , 3 ] . family history of breast cancer and gynecological variables , such as early menarche , late menopause , not bearing children , and late first pregnancy are well established risk factors for breast cancer [ 2 , 4 ] . besides these variables , according to the world cancer research fund ( wcrf ) and the american institute for cancer research ( aicr ) , drinking alcoholic beverages is a risk factor , whereas breastfeeding is a protective factor for breast cancer . however , regarding the body fatness , adult attained height , abdominal fatness , adult weight gain , and physical activity , the evidences are not sufficiently clear . body fatness is a convincing risk factor only for postmenopausal breast cancer , and the protective influence of physical activity is not convincing yet . most studies on the determinant factors for breast cancer , especially related to physical activity , have been conducted in high - income countries [ 58 ] . thus , some risk factors pointed by the wcrf and the aicr   may be different from that found in low - middle - income countries , such as brazil , which has a different epidemiological profile . in most of latin american countries , the transition experience is unlike that of the developed countries and is distinguished by the coexistence of infectious diseases and chronic diseases as important causes of death . in brazil and other latin american countries , there are few recent analytical studies on the risk and protective factors for breast cancer . according to a 2009 report by brazilian national cancer institute , in goinia , capital of gois state ( midwest of brazil ) , the estimated risk for breast cancer was 51.87 new cases per 100  000 women , which was close to the national mean estimate ( 49.27 new cases per 100  000 women ) . knowledge of risk and protective factors among populations is important to identify groups that are more susceptible and to develop strategies for primary prevention . thus , the objective of this study was to investigate some risk and protective factors for breast cancer among women from midwest of brazil and with recent diagnosis of breast cancer . this outpatient - based case - control study was conducted in 2 reference public hospitals of goinia , capital of gois state , situated in midwest of brazil . cases were interviewed at the conjunctive tissue sector and gynecology and breast clinic of arajo jorge hospital ( haj ) , a public institution that specializes in the prevention , diagnosis , and treatment of cancer , that provides health service to people from throughout midwest of brazil . cases were also interviewed at the breast service of the general hospital of the federal university of gois ( hospital das clnicas da universidade federal de gois , hc / ufg ) . controls were selected among users of the gynecology clinic at hc / ufg . both hospitals ( haj and hc / ufg ) attend to unique health system ( sus ) users , which have a similar socioeconomic profile . to calculate the sample size , the following criteria were considered : significance level of 5% , study power ( 1- ) of 80% , 2 controls for each case , an odds ratio ( or ) of 2.5 , and a prevalence of risk for consumption of alcohol among controls of 14.4% . according to these parameters , the total sample must include 186 controls and 93 cases of women with breast cancer . the inclusion and exclusion criteria ( cases and controls ) are shown in table 1 . data were collected between may 2008 and june 2010 , through a questionnaire that had been previously tested in a pilot study . this questionnaire included socioeconomic variables ( per capita income  in american dollar  education level , and area of residence ) , family history of cancer and breast cancer , gynecological variables ( number of children , age at first pregnancy , age of menarche , and age of menopause ) , breastfeeding information , anthropometric measures , alcoholic drink consumption , physical activity , and smoking habit . questions about alcoholic drink consumption , physical activity , and smoking habit were asked regarding the 6 months prior to the interview date . data on body weight and physical activity were also investigated considering the young age ( 20 years old ) . interviewees provided data on occurrence and duration of breastfeeding ( in months ) for each of their children , which were added up to provide lifetime duration of breastfeeding . anthropometric variables included height , current and previous ( at 20 years - old ) body weight , waist circumference , current and previous body mass index ( bmi ) , and adult weight gain . the first 3 variables were obtained according to the protocol reported by lohman et al . . the cut - off points used to classify nutritional status and waist circumference were established based on the world health organization . weight gain in adulthood was estimated by the difference between weight at the time of research and weight at 1820 years old . the daily intake of ethanol was calculated as follows : the amount of each alcoholic beverage consumed per week was multiplied by its alcohol content and divided by 7 . we considered only beer , because it was the only alcoholic beverage reported by consumers . the following parameters were adopted : a can of beer equivalent to 350  ml ; a bottle , 600  ml ; a glass , 250  ml . we considered the alcohol content of beer to be 5 per cent ( 5  g/100  ml )   and consumption of more than 15  g of ethanol / day as excessive consumption . the subjects were questioned about physical activity ( past 6 months ) and were classified into 4 categories : active ( moderated activities 30 minutes / session and 5 days / week , or vigorous activities 20 minutes / session and 3 days / week , or any activity adding up 150 minutes / week and 5 days / week ) ; irregularly active a ( any physical activity 150 minutes / week or 5 days / week ) ; irregularly active b ( any physical activity , but did not reach any criteria recommendation related to frequency and duration ) ; sedentary ( did not practice any physical activity at least 10 continuous minutes during the week ) . this classification was defined according to the eighth version of the international physical activity questionnaire ( ipaq ) , validated to brazilian adult women . we also evaluated previous physical activity ( at 20 years old ) , considering the practice or not of occupational , housework , and leisure physical activities . we considered smokers as those who smoked regularly for at least 1 year   and ex - smokers as those who had stopped smoking at least 2 years before the interview date . data were analyzed using statistical software for professional 8.0 ( stata corp . , college station , tx , usa ) . the normality test for quantitative variables was performed using normal curves in the stata software . variables were analyzed in the whole sample , without considering the menopausal status , like found in some studies [ 2123 ] , and because some controls did not know about their menopausal status , due to the surgical extraction of their womb . in bivariate analyses , to compare the 2 groups ( case and control ) in relation to quantitative variables , we applied student 's t - test ( parametric distribution ) and the mann whitney test ( nonparametric distribution ) . regarding the qualitative variables , we used the chi - square test or fisher 's exact test to compare case and control groups , according to frequency distribution . for all variables related to outcome , we calculated the wald statistic and the odds ratio ( or ) , with a significance level of 5% and a confidence interval ( ci ) of 95% . all variables with a p value lower than 0.20 for bivariate analyses were included in multivariate analyses . socioeconomic variables , such as education level , per capita income , and area of residence were included in the first level ( distal ) . height , physical activity , family history of cancer and of breast cancer , bearing children , and number of children were grouped in the second level ( proximal ) . bearing children and number of children , although considered as demographic variables , were included in the second level because they are influenced by socioeconomic status . variables whose p value was lower than 0.05 remained in the logistic regression model . we invited 98 cases and 186 controls to participate in research , but 5 cases ( 5.1% ) refused to be interviewed , adding up 279 women ( 93 cases and 186 controls ) . the average age among cases was 51.93 years ( range 3083 years ) and that among controls was 51.73 years ( range 2881 years ) . there were no significant differences between the case and control groups in relation to socioeconomic , gynecological , and anthropometric variables . the median family income per capita was lower than the brazilian minimum wage ( r$ 510 per month , approximately us$ 300 ) , being us$ 147 for cases ( range us$ 01,470 ) and us$ 200 for controls ( range us$ 01,029 ) ( table 2 ) . education level , per capita income , area of residence , family history of any kind of cancer , and family history of breast cancer in the first degree were significantly associated with breast cancer in the bivariate analysis ( table 3 ) . anthropometric and lifestyle variables , such as alcohol consumption , smoking habit , and physical activity , are shown in table 3 . physical activity ( past 6 months ) and previous leisure physical activity ( at 20 years old ) were associated significantly with breast cancer in the bivariate analysis ( table 4 ) . we considered the following variables in the multivariate analysis : education level , per capita income , area of residence , bearing children , number of children , family history of cancer ( any type ) , history of breast cancer , height , physical activity ( past 6 months ) , and previous occupational and leisure physical activities . after adjusting the or values , per capita income , area of residence , family history of breast cancer , physical activity ( past 6 months ) , and previous leisure physical activity remained associated with breast cancer ( table 5 ) . per capita income equal to or lower than 1/2 brazilian minimum wage ( or = 1.88 ; 95% ci = 1.063.29 ) , residence in rural area ( or = 4.93 ; 95% ci = 1.6514.73 ) , and presence of family history of breast cancer ( or = 5.38 ; 95% ci = 1.4619.93 ) were considered risk factors for breast cancer . active women were at lower risk of developing breast cancer , compared to sedentary women ( or = 0.23 ; ci = 0.100.55 ) , and that ones who had practiced leisure physical activity at young age ( 20 years - old ) were less likely to develop the disease , compared to who had ever practiced ( or = 0.13 ; ci = 0.030.54 ) ( table 5 ) . the sample was very homogeneous concerning socioeconomic , anthropometric , and gynecological variables ( table 2 ) . this can be explained by the fact that all interviews were conducted with users of public hospitals , which serve a quite similar population . women in this sample are of low socioeconomic status , which makes up 29.3% of brazilian midwest families with a per capita income of 0.51.0 minimum brazilian wage . in table 6 , we have summarized the findings of the present study , comparing to wcrf and the aicr evidences . although nutritional status was not significantly associated with breast cancer ( tables 3 and 5 ) , it is important to emphasize that the prevalence of current overweight ( bmi 25  kg / m ) in both groups ( cases and controls ) was greater than 60% , and the prevalence of obesity ( bmi 30  kg / m ) was approximately 28% among cases and 24% among controls . these values are higher than those found in brazil , since the proportion of obesity in adult brazilian women , between 2008 and 2009 , was 16.9% . obesity statistic found in this sample is troubling , because excessive body fat can promote chronic diseases such as type 2 diabetes and increase the level of proinflammatory substances that may enhance carcinogenesis . the prevalence of excessive alcoholic drinking intake was low , under 3% , for both cases and controls ( table 4 ) , and may be related with the low socioeconomic status of the sample . in the present study , we found that having a low per capita income ( under 1/2 brazilian minimum wage ) and living in a rural area were risk factors for breast cancer ( table 5 ) . one possible explanation for these findings may be the lesser access to health care and health information of poor women who live in rural areas . nevertheless , previous studies report that breast cancer is positively associated with urbanization and high socioeconomic status [ 24 ] . these associations are mainly due to variation in known risk factors , such as late pregnancy and not bearing children , found in women from urban and high - income areas . it should be added that approximately 2/3 of brazilian population is exposed to pesticides , and the most vulnerable group to this exposure is rural workers . according to peres , peres et al . the indiscriminate use of these substances by the rural population could explain the occurrence of some cancers . moreover , in most brazilian inner cities , including from gois state , a large proportion of women is from rural area , where there are no reference breast services . so that , suspected breast cancer cases move up to capital cities to receive health attendance . furthermore , it should be emphasized that goinia 's urbanization process was initiated in 1950 and occurred quickly , which was called thus , this population does not have the same characteristics as urban areas in developed countries . besides , the brazilian epidemiological transition model , called  transition polarized model ,  is different from the high - income countries models , named  classic or occidental transition model .  in the  transition polarized model ,  both chronic and infectious diseases coexist as important cause of death , and the decrease in mortality rate is slower . in the  classic or occidental transition model , therefore , risk factors may differ according to the epidemiological profile of each population [ 9 , 29 ] . we also found that family history of breast cancer in first degree is a risk factor for breast cancer ( table 5 ) , and this result is reinforced by other ones [ 12 , 30 ] . according to the  theory of two stages  in the genetic determinism of carcinogenesis , it is necessary that mutations occur at the same locus of homologous chromosomes for the development of a malignant tumor . thus , in nonhereditary cases ( also called sporadic cases ) , 2 mutagenic processes are required , whereas , in hereditary cases , 1 genetic mutation already exists and only 1 more mutation in the other chromosome is necessary . according to brandt et al . , 1520% of breast cancer cases are associated with family history of breast cancer , but only 15% can be explained by mutations in the brca1 and brca2 genes , known tumor suppressors . a woman who carries a mutation in brca-1 has a risk of 6080% for developing breast cancer [ 12 , 31 ] . regarding physical activity , we found that women who practiced at least 150 minutes / week and/or 5 days / week of physical activity were at lower risk of developing breast cancer , compared to sedentary women . moreover , that ones who practiced leisure physical activity at young age ( 20 years old ) were also at lower risk , compared to that women who did not practice leisure activity . these results show that physical activity , in general , may protect against breast cancer . this protective effect is supported by wcrf and aicr 's report and by other case - control studies [ 2 , 58 ] . this result is important because wcrf and aicr   concluded that the protective effect of physical activity is not convincing yet ( probable in postmenopausal women , but limited in premenopausal women ) , and our study supports this evidence , which may increase the consistency of this association ( table 6 ) . regular physical activity probably has a protective effect on breast cancer by delaying menarche , promoting irregular and anovulatory cycles , reducing serum estrogen , increasing globulins that bind to sex hormones , reducing inflammation , improving immune function , and helping to control weight and to improve sensitivity to insulin [ 2 , 6 ] . considering the importance of physical activity practice in prevention of breast cancer and other chronic diseases , and that health is a determinant key of development and a precursor of economic growth , it is necessary to perform programs aimed at promoting health lifestyle . to implement these policies , it is necessary the collaboration between the health sector and other key sectors , such as education , urban planning , transportation , and communication . the lack of an association of some variables with breast cancer can be explained partially by the recall bias , which is very common in case - control studies . another difficulty of case - control studies is the time required to consider exposure factors . some studies [ 22 , 33 ] considered exposure factors over 1 year . in the present study , we adopted 6 months preceding the interview to minimize memory bias . although the exposure time considered in this study was shorter than most previous case - control studies , we interviewed cases immediately after the positive diagnosis of breast cancer to avoid misconceptions about the exposure time . in fact , it represents a great strength of the present study , since in the other studies previously cited [ 22 , 33 ] , cases were interviewed 3 - 4 months after diagnosis . we recommend that other breast cancer case - control studies are conducted on populations of higher socioeconomic status from the same region of brazil . the risk and protective factors published by wcrf and aicr   may apply better to such segment of the population , because their lifestyles are more similar to those from developed countries , where most case - control and cohort studies are performed . furthermore , it is necessary to better explore the question of area of residence to clarify the association of this variable with breast cancer in the present population . this investigation is the first case - control study on the risk and protective factors for breast cancer in a population from midwest of brazil . findings from our research reinforce the associations between physical activity and family history of breast cancer , in first degree , and breast cancer . moreover , our results reveal new data that can contribute to elucidate determinant factors for breast cancer , and to prevent this disease in epidemiological transition countries , such as brazil ( table 6 ) . low per capita income , living in a rural area , and family history of breast cancer are risk factors for breast cancer , whereas practicing physical activity , including at 20 years old , is a protective factor for the disease in women from midwest of brazil .
patterns of physical activity , body composition , and breastfeeding are closely related to health and are influenced by environmental , economic , and social factors . with the increase of sedentary lifestyle and overweight , 
 many chronic diseases have also increased , including cancer . 
 breast cancer is the most common cancer in women worldwide , and the knowledge of its risk and protective factors is important to the adoption of primary prevention strategies . 
 we aimed to investigate some risk and protective factors for breast cancer among women from midwest brazil . 
 it is a case - control study of outpatient basis , carried out with 93 breast cancer cases and 186 controls . 
 socioeconomic , gynecological , anthropometric , and lifestyle variables were collected , and odds ratios ( ors ) values were estimated ( significance level , 5% ; confidence interval ( ci ) , 95% ) . per capita 
 income equal to or lower than 1/2 brazilian minimum wage ( or = 1.88 ; ci = 1.063.29 ) , residence in rural area ( or = 4.93 ; ci = 1.6514.73 ) , and presence of family history of breast cancer ( or = 5.38 ; ci = 1.4619.93 ) are risk factors for breast cancer . in turn , 
 physical activity ( past 6 months ) ( or = 0.23 ; ci = 0.100.55 ) and leisure physical activity at 20 years old ( or = 0.13 ; ci = 0.030.54 ) are protective factors for the disease in women who live in midwest of brazil .