Seasonal Variation

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 164895 Experts worldwide ranked by ideXlab platform

Ira S Ockene - One of the best experts on this subject based on the ideXlab platform.

  • Seasonal Variation in food intake physical activity and body weight in a predominantly overweight population
    European Journal of Clinical Nutrition, 2006
    Co-Authors: Barbara C Olendzki, David E Chiriboga, James R Hebert, Andrea R Hafner, Maryjane Campbell, M Sarnie, Ira S Ockene
    Abstract:

    To describe Seasonal Variation in food intake, physical activity, and body weight in a predominantly overweight population. A longitudinal observational study. Most of the study participants were recruited from a health maintenance organization (HMO) in central Massachusetts, USA. Additional individuals of Hispanic descent were recruited from outside of the HMO population to increase the ethnic diversity of this sample. Data from 593 participants, aged 20–70, were used for this investigation. Each participant was followed quarterly (five sampling points: baseline and four consecutive quarters) for 1-year period. Body weight measurements and three 24-h dietary and physical activity recalls were obtained on randomly selected days (including 2 weekdays and 1 weekend day) per quarter. Sinusoidal regression models were used to estimate peak-to-trough amplitude and phase of the peaks. Daily caloric intake was higher by 86 kcal/day during the fall compared to the spring. Percentage of calories from carbohydrate, fat and saturated fat showed slight Seasonal Variation, with a peak in the spring for carbohydrate and in the fall for total fat and saturated fat intake. The lowest physical activity level was observed in the winter and the highest in the spring. Body weight varied by about 1/2 kg throughout the year, with a peak in the winter (P<0.001 winter versus summer). Greater Seasonal Variation was observed in subjects who were male, middle aged, nonwhite, and less educated. Although there is Seasonal Variation in diet, physical activity and body weight, the magnitude of the change is generally small in this population. US National Heart, Lung and Blood Institute.

  • Seasonal Variation in serum cholesterol levels treatment implications and possible mechanisms
    JAMA Internal Medicine, 2004
    Co-Authors: Ira S Ockene, David E Chiriboga, Edward J Stanek, Morton G Harmatz, Robert J Nicolosi, Gordon M Saperia, Arnold D Well, Patty S Freedson, Philip A Merriam, George W Reed
    Abstract:

    Background A variety of studies have noted Seasonal Variation in blood lipid levels. Although the mechanism for this phenomenon is not clear, such Variation could result in larger numbers of people being diagnosed as having hypercholesterolemia during the winter. Methods We conducted a longitudinal study of Seasonal Variation in lipid levels in 517 healthy volunteers from a health maintenance organization serving central Massachusetts. Data collected during a 12-month period for each individual included baseline demographics and quarterly anthropometric, blood lipid, dietary, physical activity, light exposure, and behavioral information. Data were analyzed using sinusoidal regression modeling techniques. Results The average total cholesterol level was 222 mg/dL (5.75 mmol/L) in men and 213 mg/dL (5.52 mmol/L) in women. Amplitude of Seasonal Variation was 3.9 mg/dL (0.10 mmol/L) in men, with a peak in December, and 5.4 mg/dL (0.14 mmol/L) in women, with a peak in January. Seasonal amplitude was greater in hypercholesterolemic participants. Seasonal changes in plasma volume explained a substantial proportion of the observed Variation. Overall, 22% more participants had total cholesterol levels of 240 mg/dL or greater (≥6.22 mmol/L) in the winter than in the summer. Conclusions This study confirms Seasonal Variation in blood lipid levels and suggests greater amplitude in Seasonal variability in women and hypercholesterolemic individuals, with changes in plasma volume accounting for much of the Variation. A relative plasma hypervolemia during the summer seems to be linked to increases in temperature and/or physical activity. These findings have implications for lipid screening guidelines. Further research is needed to better understand the effects of a relative winter hemoconcentration.

  • Seasonal Variation in household occupational and leisure time physical activity longitudinal analyses from the Seasonal Variation of blood cholesterol study
    American Journal of Epidemiology, 2001
    Co-Authors: Charles E Matthews, Edward J Stanek, Patty S Freedson, Philip A Merriam, James R Hebert, Milagros C Rosal, Cara B Ebbeling, Ira S Ockene
    Abstract:

    The authors examined Seasonal Variation in physical activity in longitudinal analyses of 580 healthy adults from Worcester, Massachusetts (the Seasonal Variation of Blood Cholesterol Study, 1994-1998). Three 24-hour physical activity recalls administered five times during 12 months of follow-up were used to estimate household, occupational, leisure time, and total physical activity levels in metabolic equivalent (MET)-hours/day. Trigonometric models were used to estimate the peak-to-trough amplitude and phase of the peaks in activity during the year. Total activity increased by 1.4 MET-hours/day (121 kcal/day) in men and 1.0 MET-hours/day (70 kcal/day) in women during the summer in comparison with winter. Moderate intensity nonoccupational activity increased by 2.0-2.4 MET-hours/day in the summer. During the summer, objectively measured mean physical activity increased by 51 minutes/day (95% confidence interval: 20, 82) in men and by 16 minutes/day (95% confidence interval: -12, 45) in women. The authors observed complex patterns of Seasonal change that varied in amplitude and phase by type and intensity of activity and by subject characteristics (i.e., age, obesity, and exercise). These findings have important implications for clinical research studies examining the health effects of physical activity and for health promotion efforts designed to increase population levels of physical activity.

Peter R. Woodhouse - One of the best experts on this subject based on the ideXlab platform.

  • Seasonal Variation in 25-Hydroxyvitamin D and Parathyroid Hormone Concentrations in Healthy Elderly People
    Age and Ageing, 1994
    Co-Authors: V. Hegarty, Peter R. Woodhouse, Kay-tee Khaw
    Abstract:

    Seasonal Variation in serum 25-hydroxyvitamin D and parathyroid hormone concentration was examined longitudinally in 96 community-dwelling men and women aged 65-74 years. Mean 25-hydroxyvitamin D concentration was lowest in winter (22.7 mmol/l) and highest in summer (35.4 mmol/l); mean parathyroid hormone concentration was highest in winter (3.55 pmol/l) and lowest in summer (3.24 pmol/l): these Seasonal Variations were highly significant (p < 0.0001). Parathyroid hormone concentrations were inversely related to 25-hydroxyvitamin D concentrations (p < 0.0001). Seasonal Variation of 25-hydroxyvitamin D and parathyroid hormone concentration is marked in older healthy adults in Britain. Even in summer, mean 25-hydroxyvitamin D concentrations are low; maintaining more optimal vitamin D levels in the general population may have clinical and public health benefits.

  • Seasonal Variation of blood pressure and its relationship to ambient temperature in an elderly population
    Journal of Hypertension, 1993
    Co-Authors: Peter R. Woodhouse, Kay-tee Khaw, Martyn Plummer
    Abstract:

    Objective: To measure the magnitude and timing of Seasonal Variation of blood pressure and related factors in the elderly living in the community, and to assess their potential impact on cardiovascular risk. Design: Prospective study; from January 1991 to February 1992 blood pressure and other variables were measured at 2-monthly intervals in each subject in their own homes. Subjects: Ninety-six men and women, age range 65-74 years, recruited from a single group general practice in Cambridge. Main outcome measures: Seasonal Variation of blood pressure, Seasonal Variation of prevalence of hypertension, Seasonal Variation of ambient temperature and body mass index

G A Kerkhof - One of the best experts on this subject based on the ideXlab platform.

  • absence of Seasonal Variation in the phase of the endogenous circadian rhythm in humans
    Chronobiology International, 1998
    Co-Authors: H P A Van Dongen, G A Kerkhof
    Abstract:

    Humans may be subject to Seasonal Variations, as evidenced by the existence of Seasonal affective disorder (SAD) and midwinter insomnia. However, some recent studies have shown that the Seasonal Variation in the phase of the circadian rhythm is relatively weak in healthy humans. In the present study, evidence is found that there is no Seasonal Variation in the phase of the endogenous circadian rhythm at all. Body temperature, cortisol excretion, and subjective alertness of six subjects recorded under constant routine conditions showed no systematic Seasonal Variation in circadian phases. This finding indicates that secondary zeitgebers blocked or counterbalanced the Seasonal Variation in the entrainment effect of the natural photo-period. The human being may live in an environment in which the photoperiod has lost its status of primary zeitgeber. (Chronobiology International, 15(6), 623-632, 1998)

Ewa Magnuski - One of the best experts on this subject based on the ideXlab platform.

Martyn Plummer - One of the best experts on this subject based on the ideXlab platform.

  • Seasonal Variation of blood pressure and its relationship to ambient temperature in an elderly population
    Journal of Hypertension, 1993
    Co-Authors: Peter R. Woodhouse, Kay-tee Khaw, Martyn Plummer
    Abstract:

    Objective: To measure the magnitude and timing of Seasonal Variation of blood pressure and related factors in the elderly living in the community, and to assess their potential impact on cardiovascular risk. Design: Prospective study; from January 1991 to February 1992 blood pressure and other variables were measured at 2-monthly intervals in each subject in their own homes. Subjects: Ninety-six men and women, age range 65-74 years, recruited from a single group general practice in Cambridge. Main outcome measures: Seasonal Variation of blood pressure, Seasonal Variation of prevalence of hypertension, Seasonal Variation of ambient temperature and body mass index

Related terms

Seasonal Variation - 15 days free trial to Access Experts & Abstracts