Continuing Colorado plateau uplift by delamination-style convective lithospheric downwelling.

The Colorado plateau is a large, tectonically intact, physiographic province in the southwestern North American Cordillera that stands at ∼1,800-2,000 m elevation and has long been thought to be in isostatic equilibrium. The origin of these high elevations is unclear because unlike the surrounding provinces, which have undergone significant Cretaceous-Palaeogene compressional deformation followed by Neogene extensional deformation, the Colorado plateau is largely internally undeformed. Here we combine new seismic tomography and receiver function images to resolve a vertical high-seismic-velocity anomaly beneath the west-central plateau that extends more than 200 km in depth. The upper surface of this anomaly is seismically defined by a dipping interface extending from the lower crust to depths of 70-90 km. The base of the continental crust above the anomaly has a similar shape, with an elevated Moho. We interpret these seismic structures as a continuing regional, delamination-style foundering of lower crust and continental lithosphere. This implies that Pliocene (2.6-5.3 Myr ago) uplift of the plateau and the magmatism on its margins are intimately tied to continuing deep lithospheric processes. Petrologic and geochemical observations indicate that late Cretaceous-Palaeogene (∼90-40 Myr ago) low-angle subduction hydrated and probably weakened much of the Proterozoic tectospheric mantle beneath the Colorado plateau. We suggest that mid-Cenozoic (∼35-25 Myr ago) to Recent magmatic infiltration subsequently imparted negative compositional buoyancy to the base and sides of the Colorado plateau upper mantle, triggering downwelling. The patterns of magmatic activity suggest that previous such events have progressively removed the Colorado plateau lithosphere inward from its margins, and have driven uplift. Using Grand Canyon incision rates and Pliocene basaltic volcanism patterns, we suggest that this particular event has been active over the past ∼6 Myr.

Reported Weight Change in Older Adults and Presence of Frailty.

OBJECTIVE: A 5% change in weight is a significant predictor for frailty and obesity. We ascertained how self-reported weight change over the lifespan impacts rates of frailty in older adults. METHODS: We identified 4,984 subjects ≥60 years with body composition measures from the National Health and Nutrition Examination Survey. An adapted version of Fried's frailty criteria was used as the primary outcome. Self-reported weight was assessed at time current,1 and 10 years earlier and at age 25. Weight changes between each time point were categorized as ≥ 5%, ≤5% or neutral. Logistic regression assessed the impact of weight change on the outcome of frailty. RESULTS: Among 4,984 participants, 56.5% were female, mean age was 71.1 years, and mean BMI was 28.2kg/m2. A weight loss of ≥ 5% had a higher association with frailty compared to current weight, age 25 (OR 2.94 [1.72,5.02]), 10 years ago (OR 1.68 [1.05,2.69]), and 1 year ago (OR 1.55 [1.02,2.36]). Weight gain in the last year was associated with increased rate of frailty (1.59 [1.09,2.32]). CONCLUSION: There is an association between frailty and reported weight loss over time while only weight gain in the last year has an association with frailty.

Association of Obesity and Frailty in Older Adults: NHANES 1999-2004.

OBJECTIVES: Body composition changes with aging can increase rates of obesity, frailty and impact function. Measuring adiposity using body fat (%BF) or central adiposity using waist circumference (WC) have greater diagnostic accuracy than traditional measures such as body mass index (BMI). DESIGN: This is an observational study. SETTING: This study focused on older community-dwelling participants. PARTICIPANTS: We identified individuals age ≥ 60 years old using the 1999-2004 cross-sectional National Health and Nutrition Survey (NHANES). INTERVENTION: The primary analysis evaluated the association between frailty and %BF or WC. Frailty was the primary predictor (robust=referent) and %BF and WC were considered continuous outcomes. Multiple imputation analyses accounted for missing characteristics. MEASUREMENT: Dual energy x-ray absorptiometry was used to assess %BF and WC was objectively measured. Frailty was defined using an adapted version of Fried's criteria that was self-reported: (low BMI<18.5kg/m2; slow walking speed [<0.8m/s]; weakness [unable to lift 10lbs]; exhaustion [difficulty walking between rooms on same floor] and low physical activity [compared to others]). Robust, pre-frail and frail persons met zero, 1 or 2, and ≥3 criteria, respectively. RESULTS: Of the 4,984 participants, the mean age was 71.1±0.2 (SE) years and 56.5% were females. We classified 2,246 (50.4%), 2,195 (40.3%), and 541 (9.2%) individuals as robust, pre-frail and frail, respectively. Percent BF was 35.9±0.13, 38.3±0.20 and 40.0±0.46 in the robust, pre-frail and frail individuals, respectively. WC was 99.5±0.32 in the robust, 100.1±0.43 in pre-frail, 104.7±1.17 in frail individuals. Compared to robust individuals, only frail individuals had greater %BF on average (ß=0.97±0.43,p=0.03); however, pre-frail and frail individuals had 2.18 and 4.80 greater WC, respectively (ß=2.18±0.64,p=0.002, and ß=4.80±1.1,p<0.001). CONCLUSION: Our results demonstrate that in older adults, frailty and pre-frailty are associated with a greater likelihood of high WC (as dichotomized) and a greater average WC (continuous).

Low heart rate variability in a 2-minute rhythm strip predicts risk of coronary heart disease and mortality from several causes: the ARIC Study. Atherosclerosis Risk In Communities.

BACKGROUND: Low heart rate variability (HRV) is associated with a higher risk of death in patients with heart disease and in elderly subjects and with a higher incidence of coronary heart disease (CHD) in the general population. METHODS AND RESULTS: We studied the predictive value of HRV for CHD and death from several causes in a population study of 14 672 men and women without CHD, aged 45 to 65, by using the case-cohort design. At baseline, in 1987 to 1989, 2-minute rhythm strips were recorded. Time-domain measures of HRV were determined in a random sample of 900 subjects, for all subjects with incident CHD (395 subjects), and for all deaths (443 subjects) that occurred through 1993. Relative rates of incident CHD and cause-specific death in tertiles of HRV were computed with Poisson regression for the case-cohort design. Subjects with low HRV had an adverse cardiovascular risk profile and an elevated risk of incident CHD and death. The increased risk of death could not be attributed to a specific cause and could not be explained by other risk factors. CONCLUSIONS: Low HRV was associated with increased risk of CHD and death from several causes. It is hypothesized that low HRV is a marker of less favorable health.

Prognostic value of exercise electrocardiogram in men at high risk of future coronary heart disease: Multiple Risk Factor Intervention Trial experience.

The prognostic value of the exercise electrocardiogram was examined in the 6,438 usual care men of the Multiple Risk Factor Intervention Trial in relation to fatal and nonfatal coronary heart disease events, rest electrocardiographic abnormalities and coronary heart disease risk factors. An abnormal response to exercise, defined as an ST depression integral of 16 microV-s or more, was observed in 12.2% of the men. There was a nearly fourfold increase in 7 year coronary mortality among men with an abnormal response to exercise compared with men with a normal ST segment in exercise (risk ratio 3.8, 95% confidence limits 2.5 to 5.5). The risk ratio for coronary death, adjusted for age, diastolic blood pressure, serum cholesterol and smoking status at baseline was 3.5, and the corresponding adjusted risk ratio for death from all causes was 1.6. A similar trend toward excess coronary events was seen for angina pectoris (risk ratio of 1.6). The trend was not significant for nonfatal myocardial infarction. Multivariate analyses indicated that the ST depression integral was a strong independent predictor of future coronary death (p less than 0.001). Men with an abnormal electrocardiogram at rest (mainly high amplitude R waves) and with an abnormal ST response to exercise had an over sixfold relative risk for coronary death compared with men with an abnormal electrocardiogram at rest and a normal ST response to exercise. These results suggest that exercise testing may be indicated for improved risk assessment and the assessment of the significance of minor rest electrocardiographic abnormalities in middle-aged men with elevated levels of coronary heart disease risk factors.

Prognostic value of heart rate adjustment of exercise-induced ST segment depression in the multiple risk factor intervention trial.

OBJECTIVES: We sought to assess the effect of heart rate adjustment of ST segment depression on risk stratification for the prediction of death from coronary artery disease. BACKGROUND: Standard analysis of the ST segment response to exercise based on a fixed magnitude of horizontal or downsloping ST segment depression has demonstrated only limited diagnostic sensitivity for the detection of coronary artery disease and has variable test performance in predicting coronary artery disease mortality. Heart rate adjustment of the magnitude of ST segment depression has been proposed as an alternative approach to increase the diagnostic and prognostic accuracy of the exercise electrocardiogram (ECG). METHODS: Exercise ECGs were performed in 5,940 men from the Usual Care Group of the Multiple Risk Factor Intervention Trial at entry into the study. An abnormal ST segment response to exercise was defined according to standard criteria as > or = 100 micro V of additional horizontal or downsloping ST segment depression at peak exercise. The ST segment/heart rate index was calculated by dividing the change in ST segment depression from rest to peak exercise by the exercise-induced change in heart rate. An abnormal ST segment/heart rate index was defined as >1.60 micro V/beats per min. RESULTS: After a mean follow-up of 7 years there were 109 coronary artery disease deaths. Using a Cox proportional hazards model, a positive exercise ECG by standard criteria was not predictive of coronary mortality (age-adjusted relative risk [RR] 1.5, 95% confidence interval [CI] 0.6 to 3.6, p = 0.39). In contrast, an abnormal ST segment/heart rate index significantly increased the risk of death from coronary artery disease (age-adjusted RR 4.1, 95% CI 2.7 to 6.0, p < 0.0001). Excess risk of death was confined to the highest quintile of ST segment/heart rate index values, and within this quintile, risk was directly related to the magnitude of test abnormality. After multivariate adjustment for age, diastolic blood pressure, serum cholesterol and cigarettes smoked per day, the ST segment/heart rate index remained a significant independent predictor of coronary death (RR 3.6, 95% CI 2.4 to 5.4, p < 0.001). CONCLUSIONS: Simple heart rate adjustment of the magnitude of ST segment depression improves the prediction of death from coronary artery disease in relatively high risk, asymptomatic men. These findings strongly support the use of heart rate-adjusted indexes of ST segment depression to improve the predictive value of the exercise ECG.

Hyperinsulinemia and the development of ST-T electrocardiographic abnormalities. An 11-year follow-up study.

OBJECTIVE: It has been suggested that insulin resistance and consequent hyperinsulinemia promote atherosclerosis, but few prospective studies have reported the relationships between hyperinsulinemia and the development of ST-T abnormalities in the 12-lead resting electrocardiogram (ECG) in populations in which atherosclerosis is rare. RESEARCH DESIGN AND METHODS: A total of 304 Japanese men and women, aged 20-69 years, selected for having high blood glucose or more than a trace-positive urine glucose from a population-based health examination in 1981, were followed for 11 years. Of these, 33 died, 1 from myocardial infarction, while 260/271 living were reexamined in 1992. The 237 subjects with a normal ECG at the baseline examination were analyzed. RESULTS: Incident ST-T abnormalities occurred in 13/237 people. Insulin concentrations were positively associated with the development of ST-T abnormalities (relative risk approximately 8, comparing those in the highest versus lowest quartile of insulin values). Adjustment for age, sex, and systolic blood pressure or other risk factors had little effect on this relationship. CONCLUSIONS: Hyperinsulinemia was related to the development of ST-T abnormalities in ECGs in the absence of the development of clinical signs of atherosclerosis, independent of blood pressure and other risk factors in men and women with mild glucose intolerance.

Safety and characteristics of exercise testing early after acute myocardial infarction.

Five hundred and seventy physicians, researchers and clinicians (42% response) responded to a mailed questionnaire about the safety and nature of exercise testing conducted less than or equal to 4 weeks after acute myocardial infarction (AMI). Of 570 institutions, 193 reported that they routinely performed testing early after AMI and data were provided on 151,949 tests. A majority (111 or 58%) used a low-level testing protocol, 50 (26%) used symptom-limited testing and 32 (16%) used both types. Testing was routinely conducted less than or equal to 14 days after AMI by 147 (76%) respondents, whereas 46 (24%) tested 15 to 28 days after AMI. Thirty-three (17%) respondents used a standardized research protocol and 160 (83%) did not. There were 41 (0.03%) fatal, 141 (0.09%) major nonfatal and 2,124 (1.4%) other cardiac complications reported during testing. No difference in incidence of major complications was observed at centers using a clinical versus research protocol. Compared with clinic-based testing, hospital-based testing had an increased risk for all major (2.1) and nonfatal major complications (2.1). Although a symptom-limited protocol increased the overall risk for major cardiac complications by 1.9 times compared with a low-level protocol, the incidence of fatal complications during symptom-limited testing (0.03%) was quite low and this greater risk is of dubious clinical importance.

A new epidemiologic classification system for interim myocardial infarction from serial electrocardiographic changes.

Many clinical trials or population studies have used change in Minnesota Q code, ST-segment depression code or T-wave inversion code as evidence of new myocardial infarction or new coronary heart disease event. Direct electrocardiogram (ECG) waveform comparison is a new standardized procedure for diagnosing interim myocardial infarction from ECGs classified according to the Minnesota code (serial Q-wave pattern change). This procedure was investigated for its application in epidemiologic studies. Use of this procedure in the Multiple Risk Factor Intervention Trial resulted in a 50% increase in the positive predictive accuracy, improved agreement with clinically defined myocardial infarction and a strong independent prognostic association with total and coronary heart disease mortality. Among those with major Minnesota Q-code findings, there was substantial variation in mortality. The 5-year coronary heart disease death rates estimated by life table analysis were 8.5% for those with major serial Q-wave pattern change, 5.1% for those with minor serial Q-wave pattern change and 1.5 to 2.6% for those with major or minor Minnesota Q-code change not substantiated by direct waveform comparison, compared with 2.4% for those with no Minnesota Q-code findings. The coronary heart disease death rate for those with major serial Q-wave pattern change was greater than that for the other ECG groups (p less than 0.01). Adjustment for age and other risk factors did not qualitatively alter these findings. This new approach is eminently suitable for export to other investigators, for incorporation into computer analysis programs and for statistical analysis.

Relation between ventricular premature complexes and sudden cardiac death in apparently healthy men.

The association between ventricular premature complexes (VPCs) detected on a rest 2-minute lead I electrocardiographic rhythm strip and sudden cardiac death (SCD), occurring within 1 hour of onset of symptoms, was evaluated in a prospective study of 15,637 apparently healthy white men, aged 35 to 57 years, at the first screening examination (1973 to 1975) to determine eligibility for the Multiple Risk Factor Intervention Trial in Minneapolis/St. Paul, Minnesota. The prevalence of any VPC was 4.4% (681 of 15,637). Over an average follow-up period of 7.5 years, a total of 381 deaths occurred. Of these, 34% (131 of 381) were ascribed to coronary artery disease (CAD) and 31% of the CAD deaths (41 of 131) occurred suddenly. The presence of any VPC was associated with a significantly higher risk for SCD (adjusted relative risk = 3.0; p less than 0.025). On the other hand, the presence of any VPC was not associated with any significant increase in the risk of non-SCD or of total deaths from CAD (adjusted relative risk = 1.0 and 1.6, respectively). When VPC characteristics such as frequency (2 or more uniform VPCs every 2 minutes) and complexity (multiforms, pairs, runs, R-on-T) were examined, those with frequent or complex VPCs were at a significantly increased risk of SCD (adjusted relative risk = 4.2; p less than 0.005), whereas for non-SCD no significant increase in risk was found (adjusted relative risk = 1.6; p = 0.28).(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between electrocardiography and echocardiography for left ventricular mass in mild systemic hypertension (results from Treatment of Mild Hypertension Study).

Clinical recognition of hypertensive cardiac involvement depends primarily on use of noninvasive methods. The performance of 8 electrocardiographic (ECG) criteria sets were compared with an echocardiographic standard in the treatment of Mild Hypertension Study. Electrocardiograms were computer processed to define the following ECG criteria sets: (1) Casale/Devereux, (2) Cornell product, (3) Cornell voltage, (4) 12-lead voltage product, (5) sum of 12-lead voltage, (6) Rautaharju, (7) Sokolow-Lyon, and (8) Romhilt-Estes. Echocardiographic left ventricular (LV) mass index was calculated by using the Penn convention on a biracial population of 834 men and women. Correlations between ECG and echocardiographic LV mass index were modest (<0.40). ECG-LV hypertrophy sensitivity at 95% specificity was < 34%. The Casale/Devereux ECG criteria showed the highest average sensitivity (17%) at 95% specificity for all race-sex groups. Whites had significantly higher correlation values than blacks. ECG correlations with LV mass index were consistently improved by including systolic blood pressure and body mass index. ECG criteria sets appear to be optimized for white men. The study findings confirm the poor ECG sensitivity and correlation with echocardiographic LV mass and suggest: (1) further refinement of ECG criteria alone in white men is unlikely to improve its relationship with LV mass; and (2) combining the electrocardiogram with other non-ECG variables or noninvasive measurements offers the best strategy for improving ECG sensitivity and its prognostic value.

Prognostic associations of Minnesota Code serial electrocardiographic change classification with coronary heart disease mortality in the Multiple Risk Factor Intervention Trial.

A central requirement for epidemiologic studies and clinical trials is a bias-free, objective determination of cardiac incidence rates between comparison groups. Epidemiologic studies and clinical trials frequently use changes in the Minnesota Code to document incident ischemic events. An electrocardiographic (ECG) classification system was developed to document significant ECG pattern change using objective comparison rules for side-by-side annual ECG comparison. Previously, we showed that major evolving Q waves were strongly and independently associated with total and coronary disease mortality. Using baseline-to-annual ECG comparisons in the Multiple Risk Factor Intervention Trial, we evaluated major evolving Q waves, minor evolving Q waves combined with major evolving ST-T waves and major evolving ST-T waves alone for their prognostic associations with coronary, cardiovascular, and total mortality during 16 years of follow-up. The 16-year coronary mortality rate in men with evolving minor Q waves plus evolving ST-T waves had an average adjusted relative risk of 4, equivalent to that of a major evolving Q wave. These risk ratios held whether a clinical infarction had occurred. Silent evolving ST-T waves without Q-wave change had an average adjusted relative coronary mortality risk of 1.6. Serial comparison methodology documents additional incident ischemic ECG events beyond the traditional major Minnesota Q-code change used in older epidemiologic studies. The procedure is standardized, quantitative, and repeatable. It is applicable for any study, present or past, that used Minnesota coding. The method is also well suited for incorporation in computer analysis programs.

Validation of death certificate diagnosis of out-of-hospital sudden cardiac death.

The validity of death certificate diagnosis of out-of-hospital sudden cardiac death (OOH-SCD) was studied among 108,676 30- to 74-year-old residents in 5 Minnesota communities using 6-year mortality data (1985 to 1990). Among 4,244 total deaths, location of death was listed on the certificate as out of hospital in 2,035 cases. Of those, 911 were judged not to have OOH-SCD because they had actually been admitted to the hospital or were noncardiovascular deaths. Among the remaining 1,124, 254 were diagnosed as OOH-SCD using a thorough, physician-based procedure that used clinical records, autopsy reports, and an informant (next-of-kin) interview. We used only death certificate information to define OOH-SCD simply and inexpensively as ICD-9 code 427.5 (cardiac arrest) plus location of death listed as out-of-hospital. Compared with the physician diagnosis, sensitivity was only 24%, whereas specificity was 85%. When the definition of OOH-SCD was expanded to include ICD codes 410-414 (acute myocardial infarction and chronic coronary artery disease), sensitivity improved to 87%, whereas specificity became 66%. However, even with this higher sensitivity and specificity, only 27% of the cases labeled OOH-SCD by death certificate agreed with the physician diagnosis. Death certificate diagnosis of OOH-SCD included many erroneous cases, and may not have been suitable for study of etiologic factors, such as cardiac dysrhythmias. Death certificate diagnosis may be useful to assess population time trends in OOH-SCD, provided that misclassification (false-positive rate) remains constant over time.

Risk factors, exercise fitness and electrocardiographic response to exercise in 12,866 men at high risk of symptomatic coronary heart disease.

The association between coronary heart disease (CAD) risk factors with submaximal exercise performance was examined among 12,866 men at high risk in the Multiple Risk Factor Intervention Trial (MRFIT). Men were selected from a risk score based on serum cholesterol level, diastolic blood pressure and number of cigarettes smoked per day. Multivariate analysis using exercise ST depression as the dependent variable showed age, diastolic blood pressure and serum cholesterol level were significant positive predictors of ST depression and cigarettes per day, body mass index and heart rate at rest were significant negative predictors of ST depression. Similarly, multivariate analysis, using exercise duration as the dependent variable, revealed that age, cholesterol level, body mass index and heart rate at rest were significant negative predictors of exercise duration, whereas cigarettes per day and leisure-time physical activity were significant positive predictors. Some of these relationships with exercise performance are consistent with established epidemiologic CAD risk factor associations and others are not. The MRFIT selection process, which resulted in smokers who were significantly younger and who had significantly lower levels of other CAD risk factors than nonsmokers, was partially responsible.

Association of ventricular premature complexes with electrocardiographic-estimated left ventricular mass in a population of African-American and white men and women (The Atherosclerosis Risk in Communities.

Increased left ventricular (LV) mass is often found in adults and is a powerful predictor of cardiovascular mortality. To test the hypothesis that an electrocardiographic estimate of LV mass--the Cornell voltage--is associated with ventricular premature complexes (VPCs) in free-living adults, a cross-sectional analysis of the predictors of VPCs on a 2-minute rhythm strip in a population-based sample of 13,606 middle-aged, African-American and white men and women from 4 US communities in the Atherosclerosis Risk in Communities Study baseline examinations was performed. In adults without known coronary artery disease, the prevalence of VPCs increases monotonically with increasd Cornell voltages within ethnicity and gender groups. Independent of systemic hypertension, serum electrolytes, age, heart rate, educational attainment, gender, and ethnicity, a millivolt increase in Cornell voltage was associated with a 20% to 30% increase in the prevalence odds ratio of VPCs on the 2-minute electrocardiogram. Thus, Cornell voltage is associated with VPCs on a 2-minute electrocardiogram. The association is consistent in African-Americans, whites, men, and women.

Assessment of QT dispersion as a prognostic marker for sudden death in a regional nonreferred hypertrophic cardiomyopathy cohort.

In a consecutive, prospectively assessed and unselected hypertrophic cardiomyopathy (HC) cohort closely resembling the true disease state, QTc dispersion (and QTc) on the 12-lead electrocardiogram did not prove to be a reliable predictor of HC-related sudden death. Therefore, QT dispersion would not appear to be useful in devising future risk stratification strategies for predicting sudden death in HC.

Electrocardiographic findings in a healthy biracial population. Atherosclerosis Risk in Communities (ARIC) Study Investigators.

It has been well documented that the prevalence of certain electrocardiographic (ECG) findings among individuals free of coronary heart disease (CHD) differs by race. However, it is not known whether these differences exist independently of CHD risk factors (e.g., hypertension). We examined the ECG tracings of 2,686 apparently healthy, middle-aged African-American and white men and women who participated in the Atherosclerosis Risk in Communities Study and were at low risk of CHD. Using the Minnesota Code, among men, 46% of African-Americans, but only 25% of whites, had a minor ECG finding (p < 0.001). In women, 32% of African-Americans and 23% of whites had a minor ECG finding (p < 0.01). Specifically, the age-adjusted prevalences of high-amplitude R wave, ST elevation, T-wave findings, and prolonged P-R interval were statistically significantly higher in African-Americans. As for continuous ECG measurements, the R wave in leads V5 and V6, the S wave in V1, the J-point amplitude in leads V2 and V5, the P-R interval, and the Cornell voltage (¿S V3¿ + R aVL) for left ventricular hypertrophy were all significantly greater in African-Americans than in whites. However, in both men and women, the heart rate corrected QT interval was shorter in African-Americans than in whites. All of these findings remained statistically significant after further adjustment for traditional CHD risk factors. These results suggest that racial differences in electrocardiograms may not be explained entirely by differences in established CHD risk factors, and because current diagnostic ECG criteria are largely based on data from middle-aged white men and women, race should be considered in the interpretation of ECG findings.

The effects of diagnostic criteria on trends in coronary heart disease morbidity: the Minnesota Heart Survey.

The Minnesota Heart Survey assessed attack rates of MI in Twin Cities residents ages 30-74 years in 1970 and 1980. The age-adjusted attack rate per 100,000 of definite MI was similar in 1970 (174.2) and 1980 (179.9) p greater than 0.05, using ECG, chest pain, and blood enzyme concentrations of aspartate transaminase and/or lactic dehydrogenase as criteria. The attack rate of definite MI also remained constant when autopsy findings were included in the algorithm, 197.0 in 1970 and 191.4 in 1980 (p greater than 0.05). Adding creatine phosphokinase (CPK) and CPK-MB isoenzyme to the algorithm increased the rate of definite MIs from 209.0 in 1970 to 277.0 in 1980 (p less than 0.001). Interpretation of long-term trends in coronary heart disease morbidity is highly dependent upon variables used to validate cases. Care must be taken to maintain consistent criteria to avoid bias due to improvements in diagnostic techniques over time which increase sensitivity for detection of cardiac ischemia.

Seven-year change in graded exercise treadmill test performance in young adults in the CARDIA study. Cardiovascular Risk Factors in Young Adults.

PURPOSE: Most studies of physical fitness change have been relatively small, not population-based, and lacking in women and nonwhites. The purpose of this analysis was to evaluate the 7-yr change in physical fitness in a biracial (black and white) population of young men and women. METHODS: We evaluated change in exercise treadmill test performance in a biracial (black and white) population of 1,962 young adults, ages 18-30 yr at baseline, who completed symptom-limited graded exercise treadmill tests at the baseline (1985-1986) and year 7 (1992-1993) examinations of the CARDIA study. RESULTS: Mean test duration decreased 58 s (9.5%) over 7 yr (black men, 13.6% decrease, white men, 7.4%; black women, 11.1%; white women, 7.0%). Mean time to heart rate 130 (WL130), a measure of submaximal performance, decreased 31 s (11.3%) (black men, 16.9%; white men, 10.0%; black women, 12.3%; white women, 6.1%). Baseline body mass index (BMI) and physical activity were not statistically significant predictors of test duration change in any race-gender group, but change in BMI and activity were. Seven-year weight gain >20 lbs (31% of cohort) was associated with a large decrease in fitness (18.5% decrease in mean duration, 21.8% decrease in WL130). CONCLUSION: These data suggest that fitness declines during young adulthood in blacks and whites and that fitness changes are related to changes in weight and physical activity.

Cigarette smoking and submaximal exercise test duration in a biracial population of young adults: the CARDIA study.

Symptom-limited, graded exercise treadmill testing was performed by 4,968 white and black adults, ages 18-30 yr, during the baseline examination for the Coronary Artery Risk Development in Young Adults (CARDIA) study. Compared with nonsmokers, the mean exercise test duration of smokers was 29-64 s shorter depending on race/gender group (all P < 0.001), but mean duration to heart rate 130 (beats.min-1) ranged from 20-50 s longer (P < 0.05). In each race/gender group, test duration to heart rates up to 150 was 15-35 s longer (P < 0.05) in smokers than in nonsmokers after adjustment for age, sum of skinfolds, hemoglobin, and physical activity score. The mean maximum heart rate was lower in smokers than in nonsmokers (difference ranging from 6.7 beats.min-1 in white men to 11.2 beats.min-1 lower in black women, P < 0.001), although maximum rating of perceived exertion was nearly identical in smokers and nonsmokers. Chronic smoking appears to blunt the heart rate response to exercise, so that exercise duration to submaximal heart rates is increased even though maximal performance is impaired. This may result from downloading of beta-receptors caused by smoking. Smoking status should be considered in the evaluation of physical fitness data utilizing submaximal test protocols, or else the fitness of smokers relative to nonsmokers is likely to be overestimated.