Jeremy D. Kark

Predictors of All-Cause Mortality in Clinical Ambulatory Monitoring: Unique Aspects of Blood Pressure During Sleep

The prognostic value of sleep blood pressure reported by recent studies is variable. Our aim was to examine the relationship of sleep blood pressure, measured by 24-hour ambulatory blood pressure monitoring, with all-cause mortality. We studied a cohort of 3957 patients aged 55±16 (58% treated) referred for ambulatory monitoring (1991–2005). Sleep, including daytime sleep, was recorded by diary. Linkage with the national population register identified 303 deaths during 27 750 person-years of follow-up. Hazard ratios (HRs) for mortality in Cox proportional hazards models that included age, sex, hypertension, and diabetes treatment were 1.32 (95% CI: 0.99 to 1.76) for awake hypertension (≥135/85 mm Hg), and 1.67 (95% CI: 1.25 to 2.23) for sleep hypertension (≥120/70 mm Hg). By quintile analysis, the upper fifths of systolic and diastolic dipping during sleep were associated with adjusted HRs of 0.58 (95% CI: 0.41 to 0.82) and 0.68 (95% CI: 0.48 to 0.96), respectively. In a model controlling for awake systolic blood pressure, hazards associated with reduced systolic dipping increased from dippers (>10%; HR: 1.0), through nondippers (0% to 9.9%; HR: 1.30; 95% CI: 1.00 to 1.69) to risers (<0%; HR: 1.96; 95% CI: 1.43 to 2.96). Thus, in practice, ambulatory blood pressure predicts mortality significantly better than clinic blood pressure. The availability of blood pressure measures during sleep and, in particular, the pattern of dipping add clinically predictive information and provide further justification for the use of ambulatory monitoring in patient management.

Antioxidants in adipose tissue and risk of myocardial infarction: the EURAMIC study

Laboratory and epidemiological studies suggest that the antioxidants, vitamin E and beta-carotene, protect against coronary heart disease. In a European multicentre case-control study alpha-tocopherol and beta-carotene concentrations were measured in adipose-tissue samples collected in 1991-92 from 683 people with acute myocardial infarction and 727 controls. Mean adipose-tissue beta-carotene concentration was 0.35 microgram/g in cases and 0.42 in controls, with age-adjusted and centre-adjusted mean difference 0.07 microgram/g (95% confidence interval [CI] 0.04-0.10). Mean alpha-tocopherol concentrations were 193 micrograms/g and 192 micrograms/g for cases and controls, respectively. The age-adjusted and centre-adjusted odds ratio for risk of myocardial infarction in the lowest quintile of beta-carotene as compared with the highest was 2.62 (95% CI 1.79-3.83). Additional control for body-mass index and smoking reduced the odds ratio to 1.78 (95% CI 1.17-2.71); other established risk factors did not substantially alter this ratio. The increased risk was mainly confined to current smokers: the multivariate odds ratio in the lowest beta-carotene quintile in smokers was 2.39 (95% CI 1.35-4.25), whereas it was 1.07 for people who had never smoked. A low alpha-tocopherol concentration was not associated with risk of myocardial infarction. Our results support the hypothesis that high beta-carotene concentrations within the normal range reduce the risk of a first myocardial infarction. The findings for alpha-tocopherol are compatible with previous observations of reduced risk among vitamin E supplement users only. The consumption of beta-carotene-rich foods such as carrots and green-leaf vegetables may reduce the risk of myocardial infarction.

Telomeres shorten at equivalent rates in somatic tissues of adults

Telomere shortening in somatic tissues largely reflects stem cell replication. Previous human studies of telomere attrition were predominantly conducted on leukocytes. However, findings in leukocytes cannot be generalized to other tissues. Here we measure telomere length in leukocytes, skeletal muscle, skin and subcutaneous fat of 87 adults (aged 19–77 years). Telomeres are longest in muscle and shortest in leukocytes, yet are strongly correlated between tissues. Notably, the rates of telomere shortening are similar in the four tissues. We infer from these findings that differences in telomere length between proliferative (blood and skin) and minimally proliferative tissues (muscle and fat) are established during early life, and that in adulthood, stem cells of the four tissues replicate at a similar rate.

Genome-wide survey reveals predisposing diabetes type 2-related DNA methylation variations in human peripheral blood

Inter-individual DNA methylation variations were frequently hypothesized to alter individual susceptibility to Type 2 Diabetes Mellitus (T2DM). Sequence-influenced methylations were described in T2DM-associated genomic regions, but evidence for direct, sequence-independent association with disease risk is missing. Here, we explore disease-contributing DNA methylation through a stepwise study design: first, a pool-based, genome-scale screen among 1169 case and control individuals revealed an excess of differentially methylated sites in genomic regions that were previously associated with T2DM through genetic studies. Next, in-depth analyses were performed at selected top-ranking regions. A CpG site in the first intron of the FTO gene showed small (3.35%) but significant (P = 0.000021) hypomethylation of cases relative to controls. The effect was independent of the sequence polymorphism in the region and persists among individuals carrying the sequence-risk alleles. The odds of belonging to the T2DM group increased by 6.1% for every 1% decrease in methylation (OR = 1.061, 95% CI: 1.032-1.090), the odds ratio for decrease of 1 standard deviation of methylation (adjusted to gender) was 1.5856 (95% CI: 1.2824-1.9606) and the sensitivity (area under the curve = 0.638, 95% CI: 0.586-0.690; males = 0.675, females = 0.609) was better than that of the strongest known sequence variant. Furthermore, a prospective study in an independent population cohort revealed significant hypomethylation of young individuals that later progressed to T2DM, relative to the individuals who stayed healthy. Further genomic analysis revealed co-localization with gene enhancers and with binding sites for methylation-sensitive transcriptional regulators. The data showed that low methylation level at the analyzed sites is an early marker of T2DM and suggests a novel mechanism by which early-onset, inter-individual methylation variation at isolated non-promoter genomic sites predisposes to T2DM.

Adipose tissue isomeric trans fatty acids and risk of myocardial infarction in nine countries : the EURAMIC study

Dietary isomeric trans fatty acids-mainly produced by hydrogenation of oils-are suspected of increasing the risk of coronary heart disease. Dietary trans fatty acid intake is reflected in the fatty acid composition of adipose tissue. In an international multicentre study in eight European countries and Israel (EURAMIC), adipose tissue aspiration samples were obtained from 671 men with acute myocardial infarction (AMI), aged 70 years or less, and 717 men without a history of AMI (controls). The proportion of fatty acids, including isomeric trans monoenoic fatty acids with 18 carbon atoms (C18:1), was determined by gas chromatography. Although there were considerable differences between countries in mean (SD) proportion of adipose tissue C18:1 trans fatty acids, there was no overall difference between cases (1.61 [0.92]%) and the controls (1.57 [0.86]%). The risk of AMI did not differ significantly from 1.0 over quartiles of adipose C18:1 trans fatty acids: the multivariate odds ratio was 0.97 (95% CI 0.56-1.67) for the highest versus lowest quartile. After exclusion of subjects from Spanish centres because they had far lower proportions of adipose trans fatty acids than subjects from other countries, there was a tendency to increased risk of AMI in the upper quartiles of C18:1 trans; however, the trend was not statistically significant. Our results reflect considerable differences between countries in dietary intake of trans fatty acids but do not suggest a major overall effect of C18:1 trans fatty acids on risk of AMI. We cannot exclude the possibility that trans fatty acids have a significant impact on risk of AMI in populations with high intake.

Body-Mass Index in 2.3 Million Adolescents and Cardiovascular Death in Adulthood

BACKGROUND In light of the worldwide increase in childhood obesity, we examined the association between body-mass index (BMI) in late adolescence and death from cardiovascular causes in adulthood. METHODS We grouped data on BMI, as measured from 1967 through 2010 in 2.3 million Israeli adolescents (mean age, 17.3±0.4 years), according to age- and sex-specific percentiles from the U.S. Centers for Disease Control and Prevention. Primary outcomes were the number of deaths attributed to coronary heart disease, stroke, sudden death from an unknown cause, or a combination of all three categories (total cardiovascular causes) by mid-2011. Cox proportional-hazards models were used. RESULTS During 42,297,007 person-years of follow-up, 2918 of 32,127 deaths (9.1%) were from cardiovascular causes, including 1497 from coronary heart disease, 528 from stroke, and 893 from sudden death. On multivariable analysis, there was a graded increase in the risk of death from cardiovascular causes and all causes that started among participants in the group that was in the 50th to 74th percentiles of BMI (i.e., within the accepted normal range). Hazard ratios in the obese group (≥95th percentile for BMI), as compared with the reference group in the 5th to 24th percentiles, were 4.9 (95% confidence interval [CI], 3.9 to 6.1) for death from coronary heart disease, 2.6 (95% CI, 1.7 to 4.1) for death from stroke, 2.1 (95% CI, 1.5 to 2.9) for sudden death, and 3.5 (95% CI, 2.9 to 4.1) for death from total cardiovascular causes, after adjustment for sex, age, birth year, sociodemographic characteristics, and height. Hazard ratios for death from cardiovascular causes in the same percentile groups increased from 2.0 (95% CI, 1.1 to 3.9) during follow-up for 0 to 10 years to 4.1 (95% CI, 3.1 to 5.4) during follow-up for 30 to 40 years; during both periods, hazard ratios were consistently high for death from coronary heart disease. Findings persisted in extensive sensitivity analyses. CONCLUSIONS A BMI in the 50th to 74th percentiles, within the accepted normal range, during adolescence was associated with increased cardiovascular and all-cause mortality during 40 years of follow-up. Overweight and obesity were strongly associated with increased cardiovascular mortality in adulthood. (Funded by the Environment and Health Fund.).

Does religious observance promote health? Mortality in secular vs religious kibbutzim in Israel.

OBJECTIVES This study assessed the association of Jewish religious observance with mortality by comparing religious and secular kibbutzim. These collectives are highly similar in social structure and economic function and are cohesive and supportive communities. METHODS In a 16-year (1970 through 1985) historical prospective study of mortality in 11 religious and 11 matched secular kibbutzim in Israel, 268 deaths occurred among 3900 men and women 35 years of age and older during 41347 person-years of observation. RESULTS Mortality was considerably higher in secular kibbutzim. Cox proportional hazards analysis was used to adjust for age and the matched design; rate ratios were 1.67 (95% confidence interval [CI]=1.17, 2.39) for men, 2.67 (95% CI=1.55, 4.60) for women, and 1.93 (95% CI=1.44, 2.59) overall. Kaplan-Meier survival analysis of birth cohorts confirmed the association. The lower mortality in religious kibbutzim was consistent for all major causes of death. CONCLUSIONS Belonging to a religious collective was associated with a strong protective effect not attributable to confounding by sociodemographic factors. Elucidation of mechanisms mediating this effect may provide etiologic insights and leads for intervention.

Omega-3 Fatty Acids in Adipose Tissue and Risk of Myocardial Infarction The EURAMIC Study

Omega-3 fatty acids have potential antiatherogenic, antithrombotic, and antiarrhythmic properties, but their role in coronary heart disease remains controversial. To evaluate the association of omega-3 fatty acids in adipose tissue with the risk of myocardial infarction in men, a case-control study was conducted in eight European countries and Israel. Cases (n=639) included patients with a first myocardial infarction admitted to coronary care units within 24 hours from the onset of symptoms. Controls (n=700) were selected to represent the populations originating the cases. Adipose tissue levels of fatty acids were determined by capillary gas chromatography. The mean (+/-SD) proportion of alpha-linolenic acid was 0.77% (+/-0.19) of fatty acids in cases and 0.80% (+/-0.19) of fatty acids in controls (P=0.01). The relative risk for the highest quintile of alpha-linolenic acid compared with the lowest was 0.42 (95% confidence interval [CI] 0.22 to 0.81, P-trend=0.02). After adjusting for classical risk factors, the relative risk for the highest quintile was 0.68 (95% CI 0.31 to 1.49, P-trend=0.38). The mean proportion of docosahexaenoic acid was 0.24% (+/-0.13) of fatty acids in cases and 0.25% (+/-0.13) of fatty acids in controls (P=0. 14), with no evidence of association with risk of myocardial infarction. In this large case-control study we could not detect a protective effect of docosahexaenoic acid on the risk of myocardial infarction. The protective effect of alpha-linolenic acid was attenuated after adjusting for classical risk factors (mainly smoking), but it deserves further research.

Cigarette smoking as a risk factor for epidemic a(h1n1) influenza in young men.

We studied an outbreak of A(H1N1) influenza in an Israeli military unit of 336 healthy young men to determine the relation of cigarette smoking to the incidence of clinically apparent influenza and to the influenza-antibody response. Of 168 smokers, 68.5 per cent had influenza, as compared with 47.2 per cent of nonsmokers (P less than 0.0001). Influenza was also more severe in the smokers; 50.6 per cent of the smokers lost work days or required bed rest, or both, as compared with 30.1 per cent of the nonsmokers. The proportion of all influenza in smokers that was attributable to smoking was 31.2 per cent (95 per cent confidence intervals, 16.5 to 43.1 per cent). For severe influenza, the attributable risk in the smokers was 40.6 per cent (95 per cent confidence intervals, 21.6 to 54.8 per cent). A quarter of all severe morbidity from influenza in the overall study population was attributable to smoking. Antibody levels to A/USSR/90/77(H1N1) antigen were higher in smokers but not markedly so. We conclude that smoking is a major determinant of morbidity in epidemic influenza and may contribute substantially to incapacitation in outbreaks in populations that smoke heavily.

Nonfasting Plasma Total Homocysteine Level and Mortality in Middle-Aged and Elderly Men and Women in Jerusalem

The metabolism of homocysteine, a sulfur amino acid, is at the intersection of two metabolic pathways: transsulfuration and remethylation (1). McCully (2) first proposed that severe hyperhomocysteinemia is related to both atherosclerosis and vascular thrombosis. Recent evidence (3-5) has shown an association between mildly to moderately elevated blood concentrations of total homocysteine and vascular disease (including its coronary, cerebral, and peripheral manifestations). Much of the supporting evidence for this association has been obtained from casecontrol studies; reports of prospective studies of cardiovascular disease, however, are inconsistent (6-12). It remains to be established whether this relation is causal and whether reduction of plasma homocysteine level will decrease risk. Most studies have been done in Europe and North America. Only two recent reportsone from the Framingham Study (13) and one on patients with coronary heart disease in Norway (14)have used total mortality as an end point with which to assess health outcomes associated with a modestly elevated homocysteine level. We addressed the question of this relation in a study of nonfasting plasma homocysteine levels and 9- to 11-year all-cause mortality in a cohort of Jewish men and women 50 years of age and older living in Jerusalem. The study sample is ethnically heterogeneous, consisting mainly of persons from central and eastern Europe, northern Africa, and the Middle East who immigrated in the 1950s and 1960s, as well as those born in Israel. Methods Study Sample The third round of examinations of the Kiryat Yovel Community Health Study took place from 1985 to 1987. A neighborhood sample in western Jerusalem was identified by conducting a household census of dwelling units. All identified residents 50 years of age or older were invited for an interview and examination and were asked to give informed consent to participate (15-17). Data Collection A structured interview, administered by trained interviewers during the afternoon, was followed by an examination that included standardized measurements of blood pressure, anthropometric indexes, 12-lead electrocardiography, and a nonfasting blood sample (16, 17). Biochemical Measurements Blood was drawn into plain Vacutainers (Becton Dickinson, Carlsbad, California) and Vacutainers that contained EDTA; 90% of the samples were taken between 1:00 p.m. and 6:00 p.m. The EDTA tubes were immediately refrigerated for up to 2 to 3 hours until centrifugation. Aliquots were stored at 20 C for 9 to 11 years until they were shipped on dry ice to Boston, Massachusetts, for analysis of homocysteine. Plasma total homocysteine, the sum of protein-bound and free homocysteine, was measured by using high-performance liquid chromatography with fluorometric detection, as described by Araki and Sako (18), except for isocratic column elution. Pooled plasma was used for quality control. The interassay and intra-assay coefficient of variation for this method is less than 5%. Serum glucose level, cholesterol level, thiocyanate level, creatinine concentration, blood urea nitrogen level, and albumin level were measured on a Technicon SMAC (Technicon Instruments Corp., Tarrytown, New York). High-density lipoprotein cholesterol level was measured enzymatically (Laboratoires Biotrol, Paris, France) on a Cobas Bio autoanalyzer (F. Hoffman-La Roche Ltd., Basel, Switzerland). Physical Measurements and Interview Data Blood pressure was measured with a mercury sphygmomanometer (16). Body mass index was computed (17). Participants were asked whether a physician had ever told them that they had diabetes. They were also asked, Is your general health at present very good, good, not so good, poor, or very poor? The first two categories were combined as good health, and the last two categories were combined as poor health. Simple self-appraisals, which are common indexes of general health, are correlated with health ratings on the basis of objective measures and are predictors of subsequent death (19-23). Prevalence of cardiovascular disease was defined as typical angina (24) confirmed by a physician, reported history of heart attack, or reported history of stroke. A food-frequency questionnaire included assessment of the usual intake of fruit, fresh vegetables, and cooked vegetables. Follow-up and Causes of Death Deaths that occurred before April 1996 and the underlying cause of death as coded by the Israel Central Bureau of Statistics (International Classification of Diseases, Ninth Revision [ICD-9] codes) were identified by linkage with the national population registry. Statistical Analysis Skewed distribution of plasma homocysteine level was corrected by natural logarithmic transformation. Mean homocysteine levels, when presented, are geometric unless otherwise specified. Associations of homocysteine level with covariates were assessed by age-adjusted partial Pearson correlations and analysis of variance. Kaplan-Meier survival curves were computed for quintiles of homocysteine level after age adjustment by regression. The main analyses used Cox proportional-hazards regression to model survival according to sex-pooled quintiles of homocysteine level, adjusting for possible confounders. In these models, the outcome variable was time to event. Tests for trend were assessed with the logarithm of homocysteine level introduced as a continuous variable. Uniformity in the association of homocysteine level with survival over time was tested by introduction of time-dependent terms. Differences in hazard ratios between the sexes, age groups (<65 years of age and 65 years of age), and ethnic groups were tested by using multiplication terms. Analyses were implemented by using SPSS (SPSS, Inc., Chicago, Illinois). The population attributable fractionthat is, the proportion of all deaths in the population associated with elevated homocysteine levels (cut-off points used elsewhere [25, 26], 13 and 14 mol/L)was computed as Pe (HR 1)/1 + [Pe (HR 1)], where Pe is the proportion of patients with a plasma homocysteine level of at least 13 mol/L or at least 14 mol/L and HR is the respective hazard ratio computed from Cox models. Results Participant Characteristics All 2303 persons identified in 3434 dwelling units in the Kiryat Yovel community who were at least 50 years of age were invited to participate in our study. The response rate for the original census was 96%. A total of 1948 men and women gave informed consent and agreed to participate (85% response rate). Nonrespondents were similar to respondents with regard to age and sex. Plasma total homocysteine was measured in blood samples obtained from 1788 participants (92% of the total); the 160 participants with missing measurements did not differ significantly from those with no missing measurements with respect to age, reported diabetes, or self-appraised health. Covariate data were incomplete for 77 of the 1788 participants in the multivariate-adjusted models. The age distribution of the study sample is shown in Table 1. The mean age was 64.6 years for men and 64.5 years for women (range for both sexes, 50 to 92 years). Table 2 shows the heterogeneity of the sample with respect to place of birth and level of education. Of the 1788 participants, 13% (n=239) reported having received a physicians diagnosis of diabetes, 16% (n=283) had a history of cardiovascular disease, and 30% had hypertension (defined as systolic blood pressure 160 mm Hg, diastolic pressure 95 mm Hg, or current treatment for hypertension). Distributions of smoking and self-appraised health are shown in Table 2. Nineteen percent of men and 41% of women had a total serum cholesterol level of 6.5 mmol/L or greater ( 251 mg/dL) . The prevalence of obesity (body mass index 30.0 kg/m2) was high (32% in women and 16% in men). Table 1. Plasma Total Homocysteine Levels and Number of Deaths during 9- to 11-Year Follow-up, according to Age at Initial Examination (1985-1987) Table 2. Predictors of All-Cause Death during 9- to 11-Year Follow-up Correlates of Total Plasma Homocysteine Level We examined the relation of plasma homocysteine level to the time that had elapsed since food or drink was last consumed. A weak age-adjusted association (r=0.06; P=0.049) was restricted to women. Homocysteine levels increased with age, were higher in men than in women (Table 1), and were not significantly associated with place of birth or level of education (not shown). The strongest age-adjusted correlations were with serum creatinine concentration (r=0.21 in men and r=0.29 in women; P<0.001). The inverse relation with serum glucose level (r= 0.09 in men [P=0.011] and r= 0.15 in women [P<0.001]) was not affected by the amount of time that had passed since the participants last meal. Age- and sex-adjusted mean homocysteine levels were lower among persons who reported that they had diabetes than among those who did not (1.1 mol/L; P<0.001). Homocysteine levels were 1.1 mol/L higher in men who smoked (P=0.004) than in men who did not smoke and were positively correlated with serum thiocyanate level (r=0.12; P<0.001); these associations were weaker and nonsignificant in women. No significant associations were seen with blood pressure, body mass index, or serum lipid levels. Correlations with intake of fruit, fresh vegetables, cooked vegetables, and total vegetables were weak (r= 0.08 [P=0.045], r= 0.10 [P=0.014], r= 0.04 [P>0.2], and r= 0.10 [P=0.015], respectively, in men; r= 0.06, r= 0.04, r= 0.05, and r= 0.04, respectively, in women [for all comparisons P>0.2]). Participants with poor self-appraised health had higher age-adjusted homocysteine levels than participants in fair health or good health (1.8 mol/L and 1.5 mol/L, respectively, for men [P=0.05] and 1.0 mol/L and 0.9 mol/L, respectively, for women [P=0.2]; P=0.012 in the total sample [sex-adjusted]). Homocysteine Level and Death during 9 to 11 Years of Follow-up Among the 1788 participants,