nocturnal blood pressure dipping, acculturation, and the metabolic syndrome in hispanic women smriti...
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Nocturnal Blood Pressure Dipping, Acculturation, and the Metabolic Syndrome in
Hispanic Women
Smriti Shivpuri, M.S.
Linda C. Gallo, Ph.D.
San Diego State University/
University of California San Diego
Joint Doctoral Program in Clinical Psychology
Nocturnal Blood Pressure (NBP) Dipping
NBP dipping defined as difference between diurnal and nocturnal levels of BP
Typical NBP dipping in adults 10-20%
Classification “Non-dippers” <10% “Dippers” >/= 10% “Extreme Dippers” >20% “Reverse Dippers” higher nocturnal BP
NBP Dipping and Cardiovascular Disease (CVD) Outcomes
Non-dipping linked to increased risk of a variety of CVD outcomes: Heart failure, Myocardial Infarction1
Stroke2
Sudden Death1
Target Organ damage3
Carotid IMT4
Left ventricular hypertrophy5
Mediating physiological mechanisms poorly understood
Metabolic Syndrome (MetSyn) Syndrome characterized by constellation of risk factors of metabolic
origin
Defined by NCEP ATPIIIa as 3 of following (women):
aNational Cholesterol Education Program Adult Treatment Panel III
Elevated BP Systolic BP (SBP) ≥ 130 OR Diastolic BP (DB )P ≥ 85
Abdominal Obesity Waist Circumference > 88 cm (> 35 in)
Atherogenic Dyslipidemia HDL Cholesterol < 50 mg/d ,L Triglycerides ≥ 150 mg/dL
Insulin Resistance Fasting glucose ≥ 110 mg/dL
Metabolic Syndrome MetSyn may be mediating mechanism between NBP dipping and
CVD
Associated with almost three-fold increased risk of CVD6
Research addressing association between NBP dipping and the MetSyn is limited
Linked to NBP Dipping in some studies Greater prevalence of MetSyn in non-dippers versus dippers7,8, 9
Higher mean score of MetSyn (when measured continuously) in non-dippers than dippers10
No association in other studies11
NBP Dipping in Hispanics Evidence exists that NBP Dipping differs by race
African-Americans more likely to have “blunted” NBP Dipping than non-Hispanic Whites, and be classified as non-dippers12,13
Little to no work to date on NBP Dipping and CVD outcomes in Hispanics Some evidence that Hispanic men may be more likely to be
non-dippers than non-Hispanic Whites, but not true for Hispanic women14
One study found greater odds of stroke in nondippers versus dippers for African-Americans and non-Hispanic Whites, but not in Caribbean Hispanics15
NBP Dipping and MetSyn in Hispanics
Among ethnic minority groups in U.S., Mexican-Americans have one of highest rates of MetSyn16
No studies have looked at link between NBP Dipping and MetSyn in Hispanics or non-diseased populations, or examined whether acculturation, which has been shown to affect the relationship between risk factors and CVD outcomes, moderates relationship
Note. Image courtesy http://img.medscape.com/slide/migrated/editorial/cmecircle/2006/5186/images/caballero/slide032.gif
Current Study Purpose: To examine relationship between NBP dipping and
MetSyn in Mexican-American women and explore whether association is modified by acculturation level
Sample: 277 middle-aged (M=49.56yrs) healthy Mexican-American women, recruited from South San Diego border community Inclusion criteria: age between 40-65 years, Mexican-American
ethnicity, literate in English or Spanish, and free of major health conditions (e.g., CVD, cancer) and medications with autonomic effects
Methods: Completed battery of questionnaires assessing sociodemographic, health history/behavior, and psychosocial factors, and next day underwent assessment of MetSyn components and completed 36hr ambulatory BP (AmBP) protocol
Assessment NBP Dipping
AmBP monitor recorded participants’ BP every half hour during day, every hour during night
Resulted in an average of 60 BP readings per person over 36 hours Calculated as : (average diurnal BP - average NBP)/ average diurnal BP*100
Acculturation Measured using preferred language version of survey (commonly used proxy) Low Acculturated (Spanish) = 0; High Acculturated (English) = 1
MetSyn (defined using NCEP ATP III criteria) Waist circumference, height, weight measured by trained assessors Average SBP, DBP recorded as mean of 3 measurements while seated Glucose, HDL, triglycerides obtained through fasting blood draw
Analyses Hierarchical Linear Modeling (HLM) used to obtain average diurnal
and nocturnal BP levels across repeated measurements while accounting for nesting of measurements within individuals
Logistic Regression used to test effects of NBP dipping (SBP and DBP), acculturation, and their interaction on probability of MetSyn
Covariates (identified from prior research) included: Average daytime BP Age Body Mass Index Socioeconomic status (measured by educational attainment)
Results No significant association between Diastolic BP dipping or Diastolic
NBP dipping*Acculturation interaction and MetSyn
Significant Systolic NBP (NSBP) dipping*Acculturation interaction
95% C.I. for EXP(B)
B S.E. Wald df Sig. Exp(B) Lower Upper Age 0.037 0.027 1.931 1 0.165 1.038 0.985 1.093 Education -0.051 0.044 1.304 1 0.254 0.951 0.872 1.037 Avg Day SBP 0.035 0.015 5.067 1 0.024 1.035 1.004 1.067 BMI 0.187 0.034 29.769 1 0.000 1.206 1.128 1.29 NSBP Dipping 0.012 0.029 0.177 1 0.674 1.012 0.956 1.072 Acculturation 0.047 0.395 0.014 1 0.905 1.048 0.483 2.275 Constant -12.471 2.381 27.432 1 0 0
NSBP Dipping* Acculturation 0.163 0.063 6.841 1 0.009 1.178 1.042 1.331
Results Decreased NSBP dipping associated with increased risk for MetSyn (i.e.,
increased NSBP dipping protective), but only for high acculturated women
Odds Ratios
§
*
*
* p < .05 § p<.10
Association between Gradations of Systolic NBP (NSBP) Dipping and Odds of MetSyn in High Acculturated women
Conclusions Systolic NBP dipping associated with MetSyn in high-acculturated
but not low-acculturated Mexican-American women Each 10% decrease in dipping associated with 3.67 increased odds of
MetSyn Trend for non-dippers having three fold greater odds of MetSyn as
compared to dippers (p=.06)
Diastolic NBP dipping not associated with MetSyn
Finding suggests mechanisms by which NBP dipping relate to MetSyn may differ by acculturation
Less acculturated, more traditional women may be buffered against harmful metabolic effects of increased blood pressure load
Potential Buffering Mechanisms Sociodemographic Factors
Marital Status, Income Psychosocial Factors
Social support, Anger, Hostility, Chronic Stress, Racism Behavioral Factors
Smoking, alcohol consumption, physical activity
Addition of these factors in exploratory follow-up analyses attenuated interaction effect, but it remained statistically significant
Interestingly, for high-acculturated women NSBP dipping associated with DBP, waist circumference and HDL components of MetSyn; for low-acculturated, only waist circumference
Limitations/Future Directions Limitations
Cross-sectional study Ambulatory BP measurement for dipping only 36 hour cycle No gender or ethnic comparisons possible
Future directions Explore whether NBP dipping association with CVD outcomes varies by
acculturation status in Hispanics Determine whether NBP dipping is related to other, non-metabolic
factors in low-acculturated Hispanics (e.g., serum uric acid levels, hyperthyroidism, hyperaldosteronism)17
Cross-gender and cross-ethnic comparisons with Hispanics on association between NBP dipping and CVD outcomes
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