***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    Input: Background We investigated the association between hypertension , antihypertensive ( AH ) medication use , and breast cancer  in a large prospect i ve study , the California Teachers Study ( CTS ) . Methods Information on history of hypertension and lifetime regular use of AH medications was collected from 114,549 women in 1995–1996 . Among them , 4,151 invasive breast cancers were diagnosed between 1995 and 2006 . Additional information on AH  use was collected from 73,742 women in 2000–2001 , and 1,714 of these women were subsequently diagnosed with breast cancer . Cox proportional hazards regression was used to estimate relative risks ( RR ) and 95 % confidence intervals ( CI ) for breast cancer . Results Use of AH medication for ≥5 years , when compared with no use , was associated with a modest increased risk of invasive breast cancer ( RR = 1.18 , 95%CI 1.02–1.36 ) . This increased risk appeared to be confined to estrogen receptor (ER)-positive tumors ( RR = 1.21 , 95%CI 1.03–1.43 ) and pre-/peri-menopausal women ( RR = 1.58 , 95%CI 1.11–2.25 ) . Conclusions Increased risk of invasive breast cancer was observed for long-term ( ≥5 years ) AH use , and this appeared to be confined to ER + breast cancer and younger women Background In a recent case – control study , long-term use of calcium channel blocking drugs was associated with a greater-than-twofold increased breast cancer risk . If prospect ively collected data confirm that calcium channel blocker use increases breast cancer risk , this would have major implication s for hypertension treatment . The objective of this study was to determine whether women using calcium channel blockers for 10 years or more were at increased risk of developing breast cancer compared with women not using calcium channel blockers . Methods The Sister Study is a prospect i ve volunteer cohort study of women from the USA and Puerto Rico design ed to evaluate environmental and genetic risk factors for breast cancer . Beginning in 2003 , women between the ages of 35 and 74 were recruited . They were eligible to participate if they had a sister with breast cancer but had not been diagnosed with breast cancer themselves . In total , 50,884 women enrolled in the cohort between 2003 and 2009 ; 50,757 women with relevant baseline data and available follow-up data are included in this study . The exposure of interest is current use of calcium channel blocking drugs and the reported duration of use at entry into the cohort . Secondary exposures of interest were the duration and frequency of use for all other subclasses of antihypertensive drugs . Our main outcome is a self-reported diagnosis of breast cancer during the study follow-up period . With patient permission , self-reported diagnoses were confirmed using medical records . Results Results showed 15,817 participants were currently using an antihypertensive drug , and 3316 women were currently using a calcium channel blocker  at study baseline ; 1965 women reported a breast cancer diagnosis during study follow-up . Using Cox proportional hazards modeling , we found no increased risk of breast cancer among women who had been using calcium channel blockers for 10 years or more compared with never users of calcium channel blockers ( HR 0.88 , 95 % CI 0.58–1.33 ) . Conclusions We saw no evidence of increased risk of breast cancer from 10 years or more of current calcium channel blocker use . Our results do not support avoiding calcium channel blocking drugs in order to reduce breast cancer risk It is unclear whether hypertension and antihypertensive medication use are associated with breast cancer . In order to examine these associations , we conducted a case – control study among women aged 50–75 years . Breast cancer cases were ascertained via a population -based cancer registry ( n=523 ) and controls were ascertained via r and om-digit-dialing ( n=131 ) . Participants completed a self-administered question naire which queried history of hypertension , antihypertensive medication use and risk factors . Unconditional logistic regression was used to estimate the odds ratio ( OR ) and 95 % confidence intervals ( CI ) , adjusted for age , body mass index ( BMI ) , diabetes , smoking , alcohol use , menopausal status , family history of breast or ovarian cancer , age at first full-term pregnancy and education . History of treated hypertension was associated with significant increased risk of breast cancer ( OR , 1.77 ; 95 % CI , 1.04–3.03 ) and this association appeared only in women with BMI ⩾25 kg/m2 ( OR , 2.30 ; 95 % CI , 1.12–4.71 ) . Diuretic use was also associated with elevated breast cancer risk ( OR , 1.79 ; 95 % CI , 1.07–3.01 ) . The risk associated with diuretic use increased with duration of use ( P for trend , < 0.01 ) . Use of other blood pressure medications was not found to be associated with breast cancer risk . These results support a positive association between treated hypertension , diuretic use and breast cancer risk among women aged 50–75 years Most cross-sectional studies have shown an association between obesity and hypertension , and the prevalence of hypertension seems to increase with the degree of obesity [ 1 , 2 ] . In prospect i ve studies , obesity has been strongly related to future risk for hypertension [ 3 - 5 ] . Several clinical trials have found that short-term weight loss reduces blood pressure in hypertensive patients or persons with high normal blood pressure [ 6 - 8 ] . However , the long-term efficacy of this approach for controlling blood pressure is not well established . Because treating hypertension over a long period is costly [ 9 ] , the best approach for the control of hypertension in the general population is primary prevention . The degree to which long-term weight loss effectively prevents or delays the onset of hypertension in a normotensive population has important public health implication s. We prospect ively investigated  body mass index ( BMI ) at 18 years of age and at midlife , as well as long-term and medium-term weight changes , in relation to subsequent risk for hypertension in a large cohort of U.S. female nurses without diagnosed hypertension at baseline . In a previous analysis of this cohort [ 10 ] , higher BMI at midlife strongly increased the risk for developing hypertension during the subsequent 4 years of follow-up . However , this analysis did not examine BMI in early adulthood and weight changes in relation to the occurrence of hypertension . In the present analysis , we extended the follow-up to 16 years and included 13 120 additional incident cases of hypertension . The substantially greater power of this study allowed us to investigate the association of weight change with risk for hypertension and to examine whether weight loss could more effectively prevent hypertension in subgroups of the population ( especially those defined by baseline BMI and age ) . Methods The Nurses ' Health Study is a long-term follow-up study of female registered nurses who were 30 to 55 years of age at study entry . In 1976 , 121 700 nurses responded to a mailed question naire on medical history and health behaviors . Follow-up question naires have been sent to participants every 2 years to identify incident diagnoses of hypertension and other medical events and to up date information on risk factors . Further details have been reported elsewhere [ 11 ] . As of 1 June 1992 , the follow-up rate was 95 % of potential person-years . For the current analysis , we excluded women who , at baseline , reported high blood pressure ( or use of antihypertensive medications ) or a history of myocardial infa rct ion , angina pectoris , stroke , coronary artery surgery , diabetes mellitus , or any cancer other than nonmelanoma skin cancer ( n = 19 654 ) . If any of these conditions developed during follow-up , the women were excluded from subsequent follow-up intervals . We also excluded women for whom information on height ( n = 127 ) or weight at age 18 years ( n = 19 447 ) was missing . The analytic cohort consisted of 82 473 women . Measurement of Exposures The baseline question naire solicited information on age , current weight , height , parity , oral contraceptive use , smoking status , family history of myocardial infa rct ion , menopausal status , postmenopausal use of hormones , and other variables . Up date d information on most of these variables was collected on biennial follow-up question naires . In 1980 , we asked participants about weight at 18 years of age and current alcohol consumption . Starting in 1986 , we assessed the level of physical activity  in detail . Body mass index was used as a measure of obesity . Current BMI was up date d every 2 years by using the most recent body weight . Women were categorized into 10 groups by using whole-number cut-points of current BMI and by deciles of BMI at age 18 years to provide a reasonable number of participants in each category . The lowest category was used as the referent . We calculated long-term weight changes ( from 18 years of age to the beginning of each 2-year follow-up interval ) and medium-term weight changes ( from 1976 to the beginning of each 2-year follow-up interval ) . Women were divided into nine groups : weight loss of 10 kg or more , loss of 5.0 to 9.9 kg , loss of 2.1 to 4.9 kg , loss or gain of 2.0 kg or less , gain of 2.1 to 4.9 kg , gain of 5.0 to 9.9 kg , gain of 10.0 to 19.9 kg , gain of 20.0 to 24.9 kg , and gain of 25 kg or more . The stable weight group ( loss or gain 2.0 kg ) was the referent . For medium-term weight change , we examined the effects of weight loss sustained for a longer period by grouping women according to weight changes from 1976 to the beginning of the current interval and from 1976 to the beginning of the previous interval . Thus , in this analysis , women were categorized into a specific weight-change group only if their weight changes from 1976 to the current interval and to the previous interval fell into the same category . Otherwise , they were classified into an unstable weight group . In a sub sample of 184 participants living in the Boston area , self-reported weights were highly correlated with measured weights ( r = 0.96 ; mean difference , 1.5 kg ) [ 12 ] . In another sample of 118 younger nurses aged 25 to 42 years , recalled weights at 18 years of age were highly correlated with weights at 17 to 21 years of age that were recorded on nursing-school physical examination forms ( r = 0.87 ; mean difference , 1.4 kg ) [ 13 ] . Ascertainment of Hypertension Incident cases of hypertension were identified by self-reports of physician-diagnosed high blood pressure . On biennial follow-up question naires , we asked whether high blood pressure ( except that occurring during pregnancy ) had been diagnosed by a physician and , if so , the date of diagnosis . By 1992 , 16 395 incident cases of hypertension had been diagnosed . The validity of self-reported diagnosis of hypertension was assessed in a r and om sample of 100 nurses who had reported a diagnosis of high blood pressure on the 1982 question naire [ 14 ] . Of the 85 women who responded to a supplementary question naire , all but 1 confirmed their previous reports of hypertension ; 62 of the 85 women gave written permission for review of their medical records . We obtained records for 51 women ; all of them had  blood pressure measurements  higher than 140/90 mm Hg , and 39 ( 77 % ) had blood pressure measurements greater than 160/95 mm Hg . To investigate the likelihood of false-negative responses , blood pressure was measured in another sample of 194 nurses living in the Boston area . Among the 161 women without a previous self-report of hypertension , 7 % had a blood pressure higher than 140/90 mm Hg but none had a blood pressure greater than 160/95 mm Hg . In addition , self-reported physician diagnosis of hypertension is a strong predictor of myocardial infa rct ion and stroke in this cohort [ 15 ] ; this finding provided further biological evidence that the self-reported diagnosis of hypertension is a valid measure in our study . Statistical Analysis Follow-up started in 1976 when the baseline question naire was returned ; follow-up time accrued until the date of diagnosis of hypertension , use of antihypertensive medications , myocardial infa rct ion , angina pectoris , coronary artery surgery , stroke , diabetes mellitus , any cancer other than nonmelanoma skin cancer , death , or 1 June 1992 , whichever came first . Women were not included in the analysis during an interval if information on their current weight was missing or if they had been pregnant for at least 6 months during the previous 2-year interval . These women , however , could reenter the analyses in the subsequent follow-up intervals . Relative risk was used as the measure of association and was computed as the incidence in a specific category of BMI or weight change divided by the rate in the reference category . We used proportional hazards analyses to compute age-adjusted and multivariate-adjusted relative risks with 95 % CIs [ 16 , 17 ] . Weight change and BMI were treated as continuous variables in the models to test linear trends and to compute relative risks for each one-unit increase in BMI and weight change . We calculated the population attributable risk percentages that were attributable to long-term and medium-term weight gain compared with weight change of 2 
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In contrast , hypertension was not associated with risk of breast cancer  among premenopausal women ( RR : 0.97 ; 95 % CI : 0.84 , 1.12 ) and Asian population ( RR : 1.07 ; 95 % CI : 0.94 , 1.22).This meta- analysis collectively suggests a significantly association between hypertension and breast cancer risk , specifically for postmenopausal hypertensive women