Nocturnal Blood Pressure Dipping, Acculturation, and the Metabolic Syndrome in

Hispanic WomenSmriti 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 (DBP) ≥ 85

Abdom inal Obesity Waist Circum ference > 88 cm (> 35 in)

Atherogenic Dyslipidem ia HDL Cholesterol < 50 m g/dL, Triglycerides ≥ 150 m g/dL

Insulin Resistance Fasting glucose ≥ 110 m g/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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