***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The frequency of the 235 T and 174 M alleles of the angiotensinogen gene , previously reported to be associated with hypertension in Caucasians and Japanese , was compared between 57 hypertensive African Americans and 130 normotensive African Americans sample d as part of a community survey of hypertension in the Chicago area . The frequency of the 235 T allele was unrelated to hypertension status ( cases , 83 % , control subjects , 82 % ) , as was true for the 174 M allele . Compared with Caucasians , the frequency of the 235 T allele was twice as high in this African American population , while the frequency of the 174 M allele was similar . Even higher frequencies of the 235 T allele ( 93 % ) were noted in a sample of 122 Nigerians . It appears that the 235 T allele is very common in population s of West African origin , although we found no evidence that it confers risk of hypertension Abstract —The genes of the renin-angiotensin system have been subjected to intense molecular scrutiny in cardiovascular disease studies , but their contribution to risk is still uncertain . In this study , we sample d 192 African American and 153 European American families ( 602 and 608 individuals , respectively ) to evaluate the contribution of variations in genes that encode renin-angiotensin system components of susceptibility to hypertension . We genotyped 25 single-nucleotide polymorphisms in the renin-angiotensin system genes ACE , AGT , AGTR1 , and REN . The family-based transmission/disequilibrium test was performed with each single-nucleotide polymorphism and with the multilocus haplotypes . Two individual single-nucleotide polymorphisms were significantly associated with  hypertension among African Americans , and this result persisted when both groups were combined . The associations were confirmed in haplotype analysis for REN , AGTR1 , and ACE in African Americans . Consistent but less significant evidence was found in European Americans . We also r and omly sample d unrelated individuals across families to obtain 84 cases and 108 controls among the African Americans and 41 cases and 113 controls in the European Americans .  Single-nucleotide polymorphism and haplotype analyses again showed consistent , albeit weaker , results . Thus , in this biracial population sample , we find evidence that interindividual variation in the renin-angiotensin system genes contributes to hypertension risk BACKGROUND The angiotensin II type 1 receptor A1166C polymorphism has been associated with increased risks of hypertension and myocardial infa rct ion in several small studies . We examined the association between this polymorphism and new-onset hypertension , blood pressure ( BP ) control , and incident cardiovascular events in a large population -based cohort of older adults . METHODS Eight hundred self-identified African Americans and 1,371 r and omly selected white participants in the Cardiovascular Health Study were genotyped . The median duration of follow-up was 8.1 years . RESULTS The A1166C polymorphism was not associated with new-onset hypertension , with BP control , or with incident cardiovascular events in the overall population . In white participants , the CC genotype was associated with higher baseline systolic BP and pulse pressure , compared to the AC or AA genotype . In whites with treated hypertension at baseline , compared to the AA genotype , the CC genotype was associated with increased risks of incident congestive heart failure ( hazard ratio = 2.5 , 95 % confidence interval [ CI ] 1.3 - 4.9 ) and incident ischemic stroke ( hazard ratio = 2.6 , 95 % CI 1.1 - 6.0 ) . These associations were not observed among white participants without treated hypertension , but the interaction of genotype with treated hypertension on ischemic stroke and heart failure was only marginally significant . CONCLUSIONS On the whole , in this large cohort of older adults , the A1166C polymorphism was not associated with BP control or incident cardiovascular events . The subgroup findings in treated hypertensives need to be confirmed in additional studies 
    Output:
    
Concordance between these two population s was found for some SNPs .