If you want to view the entire study, send me a pm.
Published in Medscape:
http://www.medscape.com/viewarticle/724156?src=mp&spon=17&uac=119123DV
This study addressed the prevalence and correlates of prevalent AF in a well-defined multiracial cohort of US individuals with CKD who are not receiving long-term dialysis treatments. Most of the previous studies that examined associations between AF and CKD were conducted either in ESRD patients on dialysis or in a general population sample, or were restricted to a single racial/ethnic group.[10,13,32,33] Our study revealed 3 main findings. First, the prevalence of AF was high in this sample of participants with mild-moderate CKD, affecting nearly 1 in 5 persons overall and >1 in 4 participants ≥70 years old. This prevalence estimate is 2- to-3-fold higher than estimates from the general population using AF ascertainment methods similar to those used in our study.[8] In the REGARDS study, a national US cohort study with >30,000 participants, the prevalence of AF was only 7.8% despite the fact that REGARDS participants were approximately 7 years older than CRIC Study participants.
Second, the high prevalence of AF observed in our study sample is similar to estimates among patients with ESRD receiving long-term dialysis, which range from 13% to 23%.[10–13] This finding suggests that processes influencing the development of AF likely occur early in the course of CKD. Interestingly, when examining eGFR level and prevalent AF, the graded association with lower eGFR was no longer significant after adjustment for age, sex, race/ethnicity, and study center. Similar results were obtained when eGFR was modeled as a continuous variable (1-SD increase) or categorized into different strata (data not shown). Because CKD is substantially more common than ESRD in the United States, these findings are of particular significance from clinical and public health perspectives.
Third, risk factors for AF in this CKD population do not mirror those reported in the general population. In our multivariable logistic regression analysis, although selected risk factors for AF in the general population were independent correlates in our sample (ie, older age, heart failure, other cardiovascular disease), others were not (ie, race/ethnicity, hypertension, diabetes, body mass index, physical activity, education, hs-CRP, total cholesterol, and alcohol intake). These findings suggest the need for further investigation of the risk factors for AF in the setting of CKD, as various AF risk prediction models developed in the general population[34] may not apply.
Of interest, we found that black race was significantly associated with a higher prevalence of AF in crude analyses, but was no longer a significant correlate after adjustment for other covariates. Although this observation contrasts with the reported higher prevalence of AF among whites in the general population,[1,9,35–37] our finding is consistent with the high rate of stroke among blacks,[38] the high prevalence of AF and stroke risk factors among blacks, and the strong association between AF and stroke.[39–42] The observed prevalence of ethnic/racial distribution of AF in our study is consistent with the possibility that studies of the general population may have disproportionately underdiagnosed AF in nonwhite populations.[7,8,43] Underdiagnosis of AF in blacks might be a result of black having a higher prevalence of paroxysmal or asymptomatic AF, the difficult-to-detect patterns of AF.[7, 8] Future longitudinal evaluation of incident AF is needed among large, diverse populations with CKD to provide further clarification of the racial/ethnic epidemiology of AF in the setting of CKD.
The strong and unique association of AF with CKD could be explained by the fact that AF and CKD share a number of risk factors.[6,10,12,15–20,32] Although mechanical stress on atria due to volume overload could be the mediating factor that leads to development of AF in patients with ESRD, this may not be the case in less advanced stages. One possible mechanism for a higher prevalence of AF in early stages of CKD could be related to inflammation.[36] Elevated levels of inflammatory markers have been reported in CKD even in its early stages,[44, 45] inflammatory markers predict progression of kidney dysfunction,[46, 47] and inflammation plays a significant role in the pathogenesis of AF.[48, 49] Nevertheless, the negative association between high hs-CRP (an inflammatory marker) with AF in our study is not concordant with such an explanation. It is not clear, however, whether other inflammatory markers other than hs-CRP have stronger associations with AF or not, a possibility that needs testing.
Our results should be interpreted in the context of a number of limitations. As a cross-sectional analysis, we cannot establish a causal inference between CKD and AF or the temporal sequence of the 2 conditions. In addition, residual confounding might have affected some of the associations in the multivariable models. However, we adjusted for many of the most common risk factors for AF. Furthermore, we controlled for the geographic location of the study clinical centers (7 clinical centers) to adjust for possible differences in unmeasured characteristics of the participants related to the residence location of care.
Standard 12-lead ECG, which was 1 of the 2 AF ascertainment methods in our study, has a major limitation in detecting paroxysmal AF, which is common among CKD patients.[11, 50] We supplemented ECG data with self-reported AF to increase the sensitivity of AF ascertainment. Defining AF cases as "the presence of AF by self report and/or ECG" has been shown as a more sensitive method to detect AF.[8] Self-report is a common method for AF ascertainment in epidemiologic studies, and it is known that the associations of morbidity and mortality with self-reported AF are similar to those with ECG-detected AF.[37, 51] Having said that, because we could not validate the self-reported AF, there could be some misclassification of AF using this method, which is another study limitation.
Although it would be interesting to stratify AF correlates by the method of AF detection (ECG vs self-report), the small number of AF detected by ECG alone did not allow us to make appropriate inferences because of statistical power considerations. Despite these limitations, this analysis provided a number of significant findings that shed light on the epidemiology of AF in patients with pre-ESRD.
In conclusion, the prevalence of AF in patients with less advanced CKD is very high and is similar to that observed in patients with ESRD. Many known predictors of AF observed in the general population were not significantly correlated with AF in the setting of CKD. These findings emphasize the underappreciated clinical and public health burden of AF among individuals with CKD and the need to delineate additional predictors of developing AF in CKD to provide more robust AF risk prediction models for patients with kidney dysfunction.
[ CLOSE WINDOW ]
References
Go AS, Hylek EM, Phillips KA, et al. Prevalence of diagnosed atrial fibrillation in adults: national implications for
Published in Medscape:
http://www.medscape.com/viewarticle/724156?src=mp&spon=17&uac=119123DV
This study addressed the prevalence and correlates of prevalent AF in a well-defined multiracial cohort of US individuals with CKD who are not receiving long-term dialysis treatments. Most of the previous studies that examined associations between AF and CKD were conducted either in ESRD patients on dialysis or in a general population sample, or were restricted to a single racial/ethnic group.[10,13,32,33] Our study revealed 3 main findings. First, the prevalence of AF was high in this sample of participants with mild-moderate CKD, affecting nearly 1 in 5 persons overall and >1 in 4 participants ≥70 years old. This prevalence estimate is 2- to-3-fold higher than estimates from the general population using AF ascertainment methods similar to those used in our study.[8] In the REGARDS study, a national US cohort study with >30,000 participants, the prevalence of AF was only 7.8% despite the fact that REGARDS participants were approximately 7 years older than CRIC Study participants.
Second, the high prevalence of AF observed in our study sample is similar to estimates among patients with ESRD receiving long-term dialysis, which range from 13% to 23%.[10–13] This finding suggests that processes influencing the development of AF likely occur early in the course of CKD. Interestingly, when examining eGFR level and prevalent AF, the graded association with lower eGFR was no longer significant after adjustment for age, sex, race/ethnicity, and study center. Similar results were obtained when eGFR was modeled as a continuous variable (1-SD increase) or categorized into different strata (data not shown). Because CKD is substantially more common than ESRD in the United States, these findings are of particular significance from clinical and public health perspectives.
Third, risk factors for AF in this CKD population do not mirror those reported in the general population. In our multivariable logistic regression analysis, although selected risk factors for AF in the general population were independent correlates in our sample (ie, older age, heart failure, other cardiovascular disease), others were not (ie, race/ethnicity, hypertension, diabetes, body mass index, physical activity, education, hs-CRP, total cholesterol, and alcohol intake). These findings suggest the need for further investigation of the risk factors for AF in the setting of CKD, as various AF risk prediction models developed in the general population[34] may not apply.
Of interest, we found that black race was significantly associated with a higher prevalence of AF in crude analyses, but was no longer a significant correlate after adjustment for other covariates. Although this observation contrasts with the reported higher prevalence of AF among whites in the general population,[1,9,35–37] our finding is consistent with the high rate of stroke among blacks,[38] the high prevalence of AF and stroke risk factors among blacks, and the strong association between AF and stroke.[39–42] The observed prevalence of ethnic/racial distribution of AF in our study is consistent with the possibility that studies of the general population may have disproportionately underdiagnosed AF in nonwhite populations.[7,8,43] Underdiagnosis of AF in blacks might be a result of black having a higher prevalence of paroxysmal or asymptomatic AF, the difficult-to-detect patterns of AF.[7, 8] Future longitudinal evaluation of incident AF is needed among large, diverse populations with CKD to provide further clarification of the racial/ethnic epidemiology of AF in the setting of CKD.
The strong and unique association of AF with CKD could be explained by the fact that AF and CKD share a number of risk factors.[6,10,12,15–20,32] Although mechanical stress on atria due to volume overload could be the mediating factor that leads to development of AF in patients with ESRD, this may not be the case in less advanced stages. One possible mechanism for a higher prevalence of AF in early stages of CKD could be related to inflammation.[36] Elevated levels of inflammatory markers have been reported in CKD even in its early stages,[44, 45] inflammatory markers predict progression of kidney dysfunction,[46, 47] and inflammation plays a significant role in the pathogenesis of AF.[48, 49] Nevertheless, the negative association between high hs-CRP (an inflammatory marker) with AF in our study is not concordant with such an explanation. It is not clear, however, whether other inflammatory markers other than hs-CRP have stronger associations with AF or not, a possibility that needs testing.
Our results should be interpreted in the context of a number of limitations. As a cross-sectional analysis, we cannot establish a causal inference between CKD and AF or the temporal sequence of the 2 conditions. In addition, residual confounding might have affected some of the associations in the multivariable models. However, we adjusted for many of the most common risk factors for AF. Furthermore, we controlled for the geographic location of the study clinical centers (7 clinical centers) to adjust for possible differences in unmeasured characteristics of the participants related to the residence location of care.
Standard 12-lead ECG, which was 1 of the 2 AF ascertainment methods in our study, has a major limitation in detecting paroxysmal AF, which is common among CKD patients.[11, 50] We supplemented ECG data with self-reported AF to increase the sensitivity of AF ascertainment. Defining AF cases as "the presence of AF by self report and/or ECG" has been shown as a more sensitive method to detect AF.[8] Self-report is a common method for AF ascertainment in epidemiologic studies, and it is known that the associations of morbidity and mortality with self-reported AF are similar to those with ECG-detected AF.[37, 51] Having said that, because we could not validate the self-reported AF, there could be some misclassification of AF using this method, which is another study limitation.
Although it would be interesting to stratify AF correlates by the method of AF detection (ECG vs self-report), the small number of AF detected by ECG alone did not allow us to make appropriate inferences because of statistical power considerations. Despite these limitations, this analysis provided a number of significant findings that shed light on the epidemiology of AF in patients with pre-ESRD.
In conclusion, the prevalence of AF in patients with less advanced CKD is very high and is similar to that observed in patients with ESRD. Many known predictors of AF observed in the general population were not significantly correlated with AF in the setting of CKD. These findings emphasize the underappreciated clinical and public health burden of AF among individuals with CKD and the need to delineate additional predictors of developing AF in CKD to provide more robust AF risk prediction models for patients with kidney dysfunction.
[ CLOSE WINDOW ]
References
Go AS, Hylek EM, Phillips KA, et al. Prevalence of diagnosed atrial fibrillation in adults: national implications for
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