Temperature Extremes Associated with Premature CVD Mortality

Temperature extremes can lead to premature death due to cardiovascular disease, according to a study in Circulation: Cardiovascular Quality and Outcomes.

Researchers collected publicly available data on daily temperatures and CVD deaths between 1996 and 2004 in Brisbane, Australia. They estimated the years of life lost for each CVD death by using national age- and sex-matched life expectancies.

The relationship between temperature and years of life lost was U-shaped, with the fewest years lost at 75 degrees Fahrenheit (24 degrees Celsius). The rise in years lost was greater with hot than with cold temperatures: When the mean temperature was 90 Fahrenheit (32 Celsius), there were 45 years of life lost per day; when it was 50 Fahrenheit (10 Celsius), there were 31 years of life lost per day.

The authors note that "exposure to extreme temperatures can act as a trigger for CVD events due to changes in blood pressure, blood viscosity, blood cholesterol, and heart rate."

Work Stress Adds Modestly to Coronary Risk

Job stress contributes — albeit modestly — to coronary risk, according to a Lancet meta-analysis.

Researchers examined 13 European cohort studies conducted between 1985 and 2006 and comprising almost 200,000 people. About 15% reported job strain — the combination of high demands and low control in their work lives. By a mean follow-up of nearly 8 years, the presence of job strain at the start of the study was associated with an increased risk for coronary disease, relative to no job strain (age- and sex-adjusted hazard ratio, 1.23).

The authors estimate that roughly 3% of the coronary events in this population were attributable to job strain — a proportion much smaller than that attributed to smoking (36%), abdominal obesity (20%), and physical inactivity (12%) in previous research.

Aspirin and Cancer Mortality: New Data Indicate Modest Benefit

Daily aspirin use is associated with a modest reduction in cancer mortality, but the benefit is not as great as that observed previously, according to a prospective study in the Journal of the National Cancer Institute.

Some 100,000 adults who were free of cancer at baseline were followed for 11 years. About a quarter reported taking aspirin daily at baseline, with most continuing its use during follow-up.

Overall, 5% died from cancer during follow-up. Current daily aspirin use was associated with a small but significant reduction in overall cancer mortality, compared with nonuse (relative risk, 0.84). The lower risk was largely driven by a reduction in gastrointestinal cancer mortality, although deaths due to liver and bladder cancers were also reduced significantly.

Aspirin's benefit was limited to nonsmokers. Duration of use showed no effect.

An editorialist, a consultant to Bayer, calls the results "an echo of other data on aspirin and cancer mortality, not a resounding confirmation." He adds: "Nonetheless, the big picture on aspirin use and cancer is very positive."

Diabetes in Normal-Weight Patients Associated with Higher Mortality Risk

People who are at a normal weight when they develop diabetes have higher rates of mortality than those who are overweight or obese when diagnosed, according to an analysis of five cohort studies in JAMA.

The studies included 2500 adults over age 40 with incident diabetes; roughly 10% were normal weight. During 27,000 person-years of follow-up, adjusted hazard ratios among normal-weight patients were significantly increased for total mortality (2.08) and noncardiovascular mortality (2.32), compared with the overweight and obese group. Cardiovascular mortality was also elevated (1.52), but not significantly so.

The mechanism for the paradoxical increase is unknown and may, according to editorialists, lie in a phenotype characterized as "metabolically obese normal weight."

Glycated Hemoglobin Better Than Fasting Glucose for Predicting Cardiovascular Risk

Glycated hemoglobin levels, especially above 6.0%, are better than fasting glucose for predicting long-term cardiovascular risk, the New England Journal of Medicine reports.


Researchers measured glycated hemoglobin and fasting glucose in some 11,000 adults without diabetes or cardiovascular disease and followed them for a median of 14 years. Compared with hemoglobin levels of 5.0% to 5.5%, higher values — especially above 6% — were associated with significantly increased risks for diabetes, coronary heart disease, and stroke. Associations between hemoglobin and all-cause mortality were also significant, but formed a J-shaped curve, with the lowest and highest levels being predictive of death.


These findings held true even after adjustment for fasting glucose.


The authors say their findings "may add to the evidence supporting the use of glycated hemoglobin as a diagnostic test for diabetes."

A1C less than 4% increased mortality

Low hemoglobin A1c and risk of all-cause mortality among US adults without diabetes.
Carson AP, Fox CS, McGuire DK, Levitan EB, Laclaustra M, Mann DM, Muntner P.

Department of Epidemiology, University of Alabama at Birmingham, 35294-0022, USA. apcarson@uab.edu

Abstract
BACKGROUND: Among individuals without diabetes, elevated hemoglobin A1c (HbA1c) has been associated with increased morbidity and mortality, but the literature is sparse regarding the prognostic importance of low HbA1c.

METHODS AND RESULTS: National Health and Nutrition Examination Survey III (NHANES III) participants, 20 years and older, were followed up to 12 years (median follow-up, 8.8 years) for all-cause mortality. Cox proportional hazards regression was used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for the association between HbA1c levels and all-cause mortality for 14 099 participants without diabetes. There were 1825 deaths during the follow-up period. Participants with a low HbA1c (<4 data-blogger-escaped-.0="" data-blogger-escaped-1.25="" data-blogger-escaped-1.45="" data-blogger-escaped-2.90="" data-blogger-escaped-3.73="" data-blogger-escaped-4.0="" data-blogger-escaped-5.0="" data-blogger-escaped-5.4="" data-blogger-escaped-6.4="" data-blogger-escaped-6.76="" data-blogger-escaped-9.63="" data-blogger-escaped-95="" data-blogger-escaped-adjustment="" data-blogger-escaped-after="" data-blogger-escaped-age="" data-blogger-escaped-all-cause="" data-blogger-escaped-an="" data-blogger-escaped-and="" data-blogger-escaped-associated="" data-blogger-escaped-association="" data-blogger-escaped-attenuated="" data-blogger-escaped-between="" data-blogger-escaped-blood="" data-blogger-escaped-br="" data-blogger-escaped-but="" data-blogger-escaped-cardiovascular="" data-blogger-escaped-cell="" data-blogger-escaped-cholesterol="" data-blogger-escaped-ci="" data-blogger-escaped-compared="" data-blogger-escaped-counterparts="" data-blogger-escaped-diastolic="" data-blogger-escaped-enzymes="" data-blogger-escaped-factors="" data-blogger-escaped-ferritin="" data-blogger-escaped-for="" data-blogger-escaped-function="" data-blogger-escaped-further="" data-blogger-escaped-had="" data-blogger-escaped-hba1c="" data-blogger-escaped-highest="" data-blogger-escaped-increased="" data-blogger-escaped-indices="" data-blogger-escaped-iron="" data-blogger-escaped-levels="" data-blogger-escaped-lifestyle="" data-blogger-escaped-liver="" data-blogger-escaped-lowest="" data-blogger-escaped-mean="" data-blogger-escaped-metabolic="" data-blogger-escaped-mortality="" data-blogger-escaped-multivariable="" data-blogger-escaped-of="" data-blogger-escaped-pressure="" data-blogger-escaped-race-ethnicity="" data-blogger-escaped-red="" data-blogger-escaped-remained="" data-blogger-escaped-risk="" data-blogger-escaped-sex.="" data-blogger-escaped-significant="" data-blogger-escaped-statistically="" data-blogger-escaped-storage="" data-blogger-escaped-the="" data-blogger-escaped-their="" data-blogger-escaped-this="" data-blogger-escaped-to="" data-blogger-escaped-total="" data-blogger-escaped-versus="" data-blogger-escaped-volume="" data-blogger-escaped-was="" data-blogger-escaped-with="">
CONCLUSIONS: In this nationally representative cohort, low HbA1c was associated with increased all-cause mortality among US adults without diabetes. Additional research is needed to confirm these results and identify potential mechanisms that may be underlying this association.

A1c concentrations less than 5% had the lowest rates of cardiovascular disease and mortality.

Ann Intern Med. 2004 Sep 21;141(6):413-20.

Association of hemoglobin A1c with cardiovascular disease and mortality in adults: the European prospective investigation into cancer in Norfolk.
Khaw KT, Wareham N, Bingham S, Luben R, Welch A, Day N.

University of Cambridge, School of Clinical Medicine, Medical Research Council Epidemiology Unit, Addenbrooke's Hospital, Cambridge, United Kingdom. kk101@medschl.cam.ac.uk.

Comment in:

Ann Intern Med. 2004 Sep 21;141(6):I12.
Ann Intern Med. 2004 Sep 21;141(6):475-6.
ACP J Club. 2005 Mar-Apr;142(2):52.

Abstract
BACKGROUND: Increasing evidence suggests a continuous relationship between blood glucose concentrations and cardiovascular risk, even below diagnostic threshold levels for diabetes.

OBJECTIVE: To examine the relationship between hemoglobin A1c, cardiovascular disease, and total mortality.

DESIGN: Prospective population study.

SETTING: Norfolk, United Kingdom.

PARTICIPANTS: 4662 men and 5570 women who were 45 to 79 years of age and were residents of Norfolk.

MEASUREMENTS: Hemoglobin A1c and cardiovascular disease risk factors were assessed from 1995 to 1997, and cardiovascular disease events and mortality were assessed during the follow-up period to 2003.

RESULTS: In men and women, the relationship between hemoglobin A1c and cardiovascular disease (806 events) and between hemoglobin A1c and all-cause mortality (521 deaths) was continuous and significant throughout the whole distribution. The relationship was apparent in persons without known diabetes. Persons with hemoglobin A1c concentrations less than 5% had the lowest rates of cardiovascular disease and mortality. An increase in hemoglobin A1c of 1 percentage point was associated with a relative risk for death from any cause of 1.24 (95% CI, 1.14 to 1.34; P &lt; 0.001) in men and with a relative risk of 1.28 (CI, 1.06 to 1.32; P &lt; 0.001) in women. These relative risks were independent of age, body mass index, waist-to-hip ratio, systolic blood pressure, serum cholesterol concentration, cigarette smoking, and history of cardiovascular disease. When persons with known diabetes, hemoglobin A(1c) concentrations of 7% or greater, or a history of cardiovascular disease were excluded, the result was similar (adjusted relative risk, 1.26 [CI, 1.04 to 1.52]; P = 0.02). Fifteen percent (68 of 521) of the deaths in the sample occurred in persons with diabetes (4% of the sample), but 72% (375 of 521) occurred in persons with HbA1c concentrations between 5% and 6.9%.

LIMITATIONS: Whether HbA1c concentrations and cardiovascular disease are causally related cannot be concluded from an observational study; intervention studies are needed to determine whether decreasing HbA1c concentrations would reduce cardiovascular disease.

CONCLUSIONS: The risk for cardiovascular disease and total mortality associated with hemoglobin A1c concentrations increased continuously through the sample distribution. Most of the events in the sample occurred in persons with moderately elevated HbA1c concentrations. These findings support the need for randomized trials of interventions to reduce hemoglobin A1c concentrations in persons without diabetes.