***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    ***EXAMPLES*** 
    Input: R and om measurement error is a pervasive problem in medical research , which can introduce bias to an estimate of the association between a risk factor and a disease or make a true association statistically non-significant . Hutcheon and colleagues explain when , why , and how r and om measurement error introduces bias and provides strategies for research ers to minimise the problem BACKGROUND Previous observational studies of self-reported dairy product consumption and stroke risk have reported mixed findings . Few studies have used circulating biomarkers that provide objective measures of dairy fat intake . OBJECTIVES We tested the hypothesis that the circulating biomarkers of dairy fat , pentadecanoic acid ( 15:0 ) , heptadecanoic acid ( 17:0 ) , and trans palmitoleate ( trans 16:1n-7 ) , were associated with lower incidence of stroke , especially ischemic stroke . Secondarily , we evaluated 14:0 , which is obtained from dairy products and beef , and also endogenously synthesized . DESIGN In participants from 2 large US cohorts ( the Health Professionals Follow-Up Study : 51,529 men ; the Nurses ' Health Study : 121,700 women ) with stored blood sample s in 1993 - 1994 ( n = 18,225 ) and 1989 - 1990 ( n = 32,826 ) , respectively , we prospect ively identified 594 incident stroke cases ( median follow-up : 8.3 y ) and matched them 1:1 to risk-set- sample d control subjects by age , sex , race , and smoking . Total plasma and red blood cell ( RBC ) fatty acids were measured by using gas-liquid chromatography . Covariates were assessed by using vali date d question naires . Stroke events and subtypes were adjudicated by using medical records or other supporting documentation . We used conditional logistic regression to estimate associations of fatty acids with incident stroke , and cohort-specific findings were combined by inverse-variance weights . RESULTS After adjustment for demographic characteristics , lifestyle , cardiovascular disease risk factors , diet , and other circulating fatty acids , no significant associations with total stroke were seen for plasma 15:0 ( pooled HR for highest compared with lowest quartiles : 0.85 ; 95 % CI : 0.54 , 1.33 ) , 17:0 ( 0.99 ; 0.67 , 1.49 ) , trans 16:1 n-7 ( 0.89 ; 0.55 , 1.45 ) , or 14:0 ( 1.05 ; 0.62 , 1.78 ) . Results were similar for ischemic and hemorrhagic stroke subtypes , for RBC fatty acids , and in several different sensitivity analyses . CONCLUSION In 2 large prospect i ve cohorts , circulating biomarkers of dairy fat were not significantly associated with stroke BACKGROUND AND PURPOSE High intakes of calcium , potassium , and magnesium have been hypothesized to reduce risks of cardiovascular disease , but only a few prospect i ve studies have examined intakes of these cations in relation to risk of stroke . METHODS In 1980 , 85 764 women in the Nurses ' Health Study cohort , aged 34 to 59 years and free of diagnosed cardiovascular disease and cancer , completed dietary question naires  from which we calculated intakes of calcium , potassium , and magnesium . By 1994 , after 1.16 million person-years of follow-up , 690 incident strokes ( 129 subarachnoid hemorrhages , 74 intraparenchymal hemorrhages , 386 ischemic strokes , and 101 strokes of undetermined type ) had been documented . RESULTS Intakes of calcium , potassium , and magnesium were each inversely associated with age- and smoking-adjusted relative risks of ischemic stroke , excluding embolic infa rct ion of nonatherogenic origin ( n=347 ) . Adjustment for other cardiovascular risk factors , including history of hypertension , attenuated these associations , particularly for magnesium intake . In a multivariate analysis , women in the highest quintile of calcium intake had an adjusted relative risk of ischemic stroke of 0.69 ( 95 % CI , 0.50 to 0.95 ; P for trend=0.03 ) compared with those in the lowest quintile ; for potassium intake the corresponding relative risk was 0.72 ( 95 % CI , 0.51 to 1.01 ; P for trend=0.10 ) . Further simultaneous adjustment for calcium and potassium intake suggested an independent association for calcium intake . The association of risk with calcium intake did not appear to be log linear ; the increase in risk was limited to the lowest quintile of intake , and intakes > approximately 600 mg/d did not appear to reduce risk of stroke further . The inverse association with calcium intake was stronger for dairy than for nondairy calcium intake . Intakes of calcium , potassium , and magnesium were not related to risk of other stroke subtypes . CONCLUSIONS Low calcium intake , and perhaps low potassium intake , may contribute to increased risk of ischemic stroke in middle-aged American women . It remains possible that women in the lowest quintile of calcium intake had unknown characteristics that made them susceptible to ischemic stroke Background Evidence regarding the role of dairy fat intake in  cardiovascular disease (  CVD ) has been mixed and inconclusive . Most earlier studies have used self‐reported measures of dietary intake and focused on relatively racially homogeneous population s. Circulating biomarkers of dairy fat in a multiethnic cohort provide objective measures of dairy fat intake and facilitate conclusions relevant to population s with different diets and susceptibility to CVD . Methods and Results In a multiethnic cohort of 2837 US adults aged 45 to 84 years at baseline ( 2000–2002 ) , phospholipid fatty acids including 15:0 , 14:0 , and trans‐16:1n7 were measured using st and ardized methods , and the incidence of CVD prospect ively adjudicated . Self‐reported whole‐fat dairy and butter intakes had strongest associations with 15:0 , rather than 14:0 or trans‐16:1n7 . In multivariate models including demographics and lifestyle and dietary habits , each SD‐unit of 15:0 was associated with 19 % lower CVD risk ( hazard ratio [ 95 % CI ] 0.81 [ 0.68 to 0.98 ] ) and 26 % lower coronary heart disease ( CHD ) risk ( 0.74 [ 0.60 to 0.92 ] ) . Associations were strengthened after mutual adjustment for 14:0 and trans‐16:1n‐7 and were similar after adjustment for potential mediators . Plasma phospholipid 14:0 and trans‐16:1n‐7 were not significantly associated with incident CVD or CHD . All findings were similar in white , black , Hispanic , and Chinese American participants .  Conclusion Plasma phospholipid 15:0 , a biomarker of dairy fat , was inversely associated with incident CVD and CHD , while no association was found with phospholipid 14:0 and trans‐16:1n‐7 . These findings support the need for further investigation of CVD effects of dairy fat , dairy‐specific fatty acids , and dairy products in general A major problem in review ing the published results of different epidemiologic studies of the relation between a quantitative variable and the risk of disease is that the results are presented in many different ways . The purpose of this paper is to exemplify methods by which results expressed either as risks ( or rates ) according to quantlle groups of the quantitative variable or as results derived from a  logistic regression analysis can be reexpressed in a uniform manner , as a mean difference in the quantitative variable between the cases of disease and the other subjects in the study . An important assumption of the methods is that the quantitative variable has an approximately normal distribution , and a way of investigating the appropriateness of this assumption is given . The methods can be applied to both prospect i ve and case-control studies and are exemplified by a number of studies of serum albumin concentrations and mortality . In some applications , these methods can be used as a precursor to formal meta- analysis , for example , when differential control of potential confounding factors is not a problem . At the least , the methods can be useful either in quantitatively review ing published studies before undertaking new research or in putting the results of a new study into the context of previously published ones BACKGROUND Although trans fatty acids ( TFAs ) may increase the risk of dyslipidemia and coronary artery disease ( CAD ) , limited data are available on their association with heart failure ( HF ) . OBJECTIVE Our goal was to assess associations of plasma and dietary TFAs with HF and CAD . DESIGN We used a prospect i ve , nested case-control design to select 788 incident HF cases and 788 matched controls from the Physicians ' Health Study for biomarker analyses and a prospect i ve cohort for the dietary analyses .  Plasma fatty acids were assessed by using gas chromatography , and dietary intake was estimated by using a food-frequency question naire . Self-reported HF was ascertained by using annual follow-up question naires with validation in a sub sample . We used conditional logistic ( or Cox ) regression to estimate multivariable-adjusted ORs ( or HRs ) for HF and CAD . RESULTS Multivariable-adjusted ORs ( 95 % CIs ) for HF across consecutive quintiles of plasma trans 18:2 ( linoleic acid ) fatty acids were 1.0 ( reference ) , 1.10 ( 0.79 , 1.54 ) , 0.88 ( 0.62 , 1.25 ) , 0.71 ( 0.49 , 1.02 ) , and 0.67 ( 0.45 , 0.98 ) ( P-trend = 0.01 ) . Each SD of plasma trans 18:2 was associated with a 22 % lower risk of HF ( 95 % CI : 6 % , 36 % ) . Plasma trans 16:1 and 18:1 were not associated with risk of HF ( P > 0.05 ) . Dietary trans fats were not associated with incident HF or CAD . CONCLUSIONS Our data are consistent with a lower risk of HF with higher concentrations of plasma trans 18:2 but not with trans 16:1 or trans 18:1 fatty acids in male physicians .  Dietary TFAs were not related to incident HF or CAD BACKGROUND Some previous prospect i ve studies showed that dietary intake of omega3 polyunsaturated fatty acids was associated with lower risk of heart failure ( HF )  , but no study has examined the association between plasma fatty acids and HF . METHODS We included 3,592 white participants from the Minneapolis field center of the Atherosclerosis Risk in Communities ( ARIC ) Study , aged 45 to 64 at baseline ( 1987 - 1989 ) , initially free of coronary heart disease , stroke , and HF and who had cholesterol ester and phospholipid plasma fatty acids measured . Participants were followed through 2003 , and incident HF was defined by a hospital discharge or death including a HF International Classification of Diseases code . RESULTS During the 14.3-year follow-up , we identified 197 cases of HF ( 110 for men and 87 for women ) . After adjustment for age and other confounders , higher saturated fatty acids , especially myristic ( 14:0 ) acid , were associated positively with incident HF in both men and women . Higher arachidonic ( 20:3,omega6 ) and long-chain omega3 polyunsaturated fatty acids , especially docosahexaenoic ( 22:6,omega3 ) acid , were associated inversely with HF in women but not in men . Neither plasma alpha-linolenic nor eicosapentaenoic acid was associated with incident HF . CONCLUSIONS In both men and women , greater levels of saturated fatty acids may increase risk of HF . In women , arachidonic acid and long-chain omega3 polyunsaturated fatty acids may decrease risk of HF Background and Purpose — Although studies have linked types of fatty acids with coronary heart disease , data on individual fatty acids and risk of ischemic stroke are limited . We aim ed to examine the associations between serum fatty acid concentrations and incidence of ischemic stroke and its subtypes . Methods — We conducted a prospect i ve case – control study nested in the Women ’s Health Initiative Observational Study cohort of postmenopausal US women aged 50 to 79 years . Between 1993 and 2003 , incident cases of ischemic stroke were matched 1:1 to controls on age , race , and length of follow-up ( 964 matched pairs ) . Conditional logistic regression was used to estimate odds ratios and 99.9 % confidence intervals ( CI ) for ischemic stroke and its subtypes . Results — The multivariable-adjusted odds ratios and 99.9 % CI of ischemic stroke associated with a 1-SD increment in serum fatty acid concentration were 1.38 ( 99.9 % CI , 1.05–1.83 ) for linoelaidic acid ( 18:2tt , SD=0.04 % ) , 1.27 ( 99.9 % CI , 1.06–1.51 ) for palmitic acid ( 16:0 , SD= 
    Output:
    
Conclusion :  Higher dairy fat exposure  is not associated with an increased risk of CVD