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Relation of Season and Temperature to Endothelium-Dependent Flow-Mediated Vasodilation in Subjects Without Clinical Evidence of Cardiovascular Disease (from the Framingham Heart Study)

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Multiple studies have documented an increased incidence of cardiovascular events in the winter, but the pathophysiologic mechanisms remain incompletely understood. It was hypothesized that brachial flow and flow-mediated dilation (FMD) would vary by season and temperature. Season and temperature were related to ultrasonic brachial artery endothelium-dependent FMD% (n = 2,587), baseline flow velocity, and maximal reactive hyperemia (n = 1,973) in the Framingham Offspring Cohort (mean age 61 ± 10 years, 53% women). Outdoor temperatures were obtained from National Climate Data Center records for Bedford, Massachusetts (about 14 miles from the testing site), and the examination room temperature was measured. In multivariate models, FMD% was highest in summer and lowest in winter (3.01 ± 0.09% vs 2.56 ± 0.10%, respectively, p = 0.02 for differences across all 4 seasons). FMD% was highest in the warmest and lowest in the coldest outdoor-temperature quartiles. In stepwise models adjusting for risk factors and selecting among season, outdoor temperature, and room temperature, FMD% was associated with season (p = 0.02); temperature did not enter the model. In contrast, hyperemic flow velocity was significantly lower for cooler and higher for warmer room temperatures (p = 0.02 overall); season did not enter the model. Season and outdoor and room temperature were each retained in a stepwise model of baseline flow velocity (p <0.0001, p = 0.02, and p <0.0001, respectively). In conclusion, a significant association was observed between season and FMD%. Microvascular vasodilator function, as reflected by hyperemic flow velocity, was more strongly related to temperature than season. Endothelial dysfunction may be 1 of the mechanisms influencing seasonal variation in cardiovascular events.

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Participants

The design of the Framingham Offspring Study has been described elsewhere.15 Participants receiving the seventh examination (1998 to 2001) were eligible for the present investigation (n = 3,539; 86% of those alive at examination 7). A total of 2,587 participants (73% of those eligible) were available for FMD analyses after exclusions for the following indications: room temperature not recorded at the time of examination (n = 237), missing data for outdoor temperature on examination day (n =

Participant characteristics

Characteristics of the 2,587 eligible participants (1,973 with flow velocity data) from the Framingham Offspring Cohort (53% women, mean age 61 ± 10 years), categorized by season, are listed in Table 1. The vascular measurements were made from 8 a.m. to 1 p.m., and the mean time of the study did not vary according to season (p = 0.55). In winter, participants had higher systolic and diastolic blood pressures (unadjusted). Participants examined during winter and spring were younger than those

Discussion

In the Framingham Offspring Cohort, we observed that brachial artery FMD was lowest in winter and that the relation between season and this measure of conduit artery endothelial function remained significant after adjusting for clinical covariates and baseline flow velocity. Whereas conduit artery dilator function related most strongly to season, we observed that microvascular vasodilator function, as assessed by hyperemic flow, was more strongly related to ambient temperature. Thus, reactive

Refrence (30)

  • N. Gokce et al.

    Acute effects of vasoactive drug treatment on brachial artery reactivity

    J Am Coll Cardiol

    (2002)
  • A.E. Kunst et al.

    Outdoor air temperature and mortality in The Netherlands: a time-series analysis

    Am J Epidemiol

    (1993)
  • T.L. Visscher et al.

    Time trends (1993–1997) and seasonal variation in body mass index and waist circumference in the Netherlands

    Int J Obes Relat Metab Disord

    (2004)
  • J. Minami et al.

    Seasonal variations in office, home and 24 h ambulatory blood pressure in patients with essential hypertension

    J Hypertens

    (1996)
  • I.S. Ockene et al.

    Seasonal variation in serum cholesterol levels: treatment implications and possible mechanisms

    Arch Intern Med

    (2004)
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    This study was supported by Grants N01-HC 25195, HL60040, HL70100, and K24-HL-04334 (to Dr. Vasan) from the National Heart, Lung, and Blood Institute, Bethesda, Maryland, and the Donald W. Reynolds Foundation, Las Vegas, Nevada. Cardiovascular Engineering, Inc., Waltham, Massachusetts, provided image-capture software.

    Conflict of interest: Dr. Mitchell is president of Cardiovascular Engineering, Inc.

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