Seasonal variation of serum lipids in an elderly population

Physiological Rhythms and Biological Variation of Biomolecules: The Road to Personalized Laboratory Medicine

The concentration of biomolecules in living systems shows numerous systematic and random variations. Systematic variations can be classified based on the frequency of variations as ultradian (<24 h), circadian (approximately 24 h), and infradian (>24 h), which are partly predictable. Random biological variations are known as between-subject biological variations that are the variations among the set points of an analyte from different individuals and within-subject biological variation, which is the variation of the analyte around individuals’ set points. The random biological variation cannot be predicted but can be estimated using appropriate measurement and statistical procedures. Physiological rhythms and random biological variation of the analytes could be considered the essential elements of predictive, preventive, and particularly personalized laboratory medicine. This systematic review aims to summarize research that have been done about the types of physiological rhythms, biological variations, and their effects on laboratory tests. We have searched the PubMed and Web of Science databases for biological variation and physiological rhythm articles in English without time restrictions with the terms “Biological variation, Within-subject biological variation, Between-subject biological variation, Physiological rhythms, Ultradian rhythms, Circadian rhythm, Infradian rhythms”. It was concluded that, for effective management of predicting, preventing, and personalizing medicine, which is based on the safe and valid interpretation of patients’ laboratory test results, both physiological rhythms and biological variation of the measurands should be considered simultaneously.

Effects of ambient temperature on cardiovascular disease: a time-series analysis of 229288 deaths during 2009-2017 in Qingdao, China

The association between ambient temperature and cardiovascular mortality varied by regions, populations, and climates. We estimated the relative risk (RR) of cardiovascular mortality using 229,288 death cases of cardiovascular disease in Qingdao China from 1 January 2009, to 31 December 2017. A distributed lag non-linear model was used. The temperature showed a negative association with the cardiovascular mortality. The RR of cardiovascular death at -4.8 °C was 2.05 (95% CI: 1.55, 2.69). The high temperature had acute and short-term effects with the maximum risk occurring 0 day of exposure. The low temperature had the greatest effect on the 4th lag day. The cold temperature effect was stronger for males than females. The estimates of temperature-related cardiovascular mortality risk were higher in people age ≥75 years. Our study showed that the cold and hot ambient temperature had a relationship with the risk of cardiovascular mortality.

Data mining: traditional spring festival associated with hypercholesterolemia

BACKGROUND

Serum lipid concentrations are affected by long-term high-fat diets; thus, we hypothesize that lipid levels increase after the Spring Festival in China.

METHOD

In total, 20,192 individuals (male: n=10,108, female: n=10,084) were enrolled in this retrospective cross-sectional study based on clinical data from the Laboratory Information System (LIS) and Hospital Information System (HIS) in Peking Union Medical College Hospital from 2014 to 2018. Total cholesterol (TC), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were analyzed.

RESULTS

The serum TC [male vs. female: (4.71 ± 0.90 vs. 4.56 ± 0.85) mmol/L], TG [male vs. female: (1.71 ± 1.56 vs. 1.02 ± 0.68) mmol/L], and LDL-C [male vs. female: (3.01 ± 0.77 vs. 2.73 ± 0.74) mmol/L] levels were significantly higher in males than in females (P < 0.001); serum HDL-C [male vs. female: (1.18 ± 0.28 vs. 1.50 ± 0.34) mmol/L] was significantly lower in males (P < 0.001). In February, the TC, TG, and LDL-C levels were 8.4%, 16.3%, and 9.3% higher than the lowest levels recorded, respectively. The prevalence of dyslipidemia of the two weeks before the Spring festival was significantly lower than that of the first week after the Spring festival (43.6% (168/385) vs. 54.1% (126/233), P=0.007). Additionally, the prevalence of dyslipidemia was statistically higher in the first week after the Spring Festival than in May-January.

CONCLUSION

Higher TC, TG, and LDL-C in winter could be associated with high-fat diets during the Spring Festival. The Spring Festival was immediately followed by a higher lipid concentrations. Thus, we don't recommend lipid assessment or physical examination immediately after the holiday especially Spring festival.

Physiological and hematological responses to cold exposure in young subjects

BACKGROUND

In this study we have investigated the effect of cold exposure on young healthy subjects, with particular emphasis on the hematological system.

STUDY DESIGN

The lightly clothed subjects were seated in a thermally controlled climatic chamber for three hours.

METHODS

One group (control) was exposed to three hours at 28 degrees C, while the other group was first exposed to one hour at 28 degrees C, and then two hours of decreasing temperature, ending at 6 degrees C. Mean body temperature decreased, blood pressure increased, and metabolism increased by 60% in the cold exposure group compared to the control group. Blood samples were taken through an arterial catheter every hour during the exposure, one hour before and 1.5, 3 and 25 hours after the exposure.

RESULTS

Red blood cell counts increased, due to hemo-concentration. In the cold neutrophil counts did not increase during the day, but were stable at a lower level compared to the controls.

CONCLUSIONS

It is suggested that the cold induced decrease in neutrophil count is caused by an activation and increased adhesion of the neutrophils to the endothelial wall. This finding is supported by the cold exposure-induced increases in IL-8 and Thromboxane B2 in LPS-stimulated blood, and an increase in the plasma concentration of P-selectin.

[Occurrence of acute cardiovascular diseases under different atmospheric parameters]

INTRODUCTION

Research on the effects of meteorological parameters on cardiovascular diseases may allow the development of novel prevention strategies.

AIM

The aim of the authors was to examine the correlation between meteorological parameters and the occurrence of acute cardiovascular diseases.

METHOD

A retrospective analysis was performed in 343 patients diagnosed with acute cardiovascular disease and treated at the Department of Vascular Surgery, Semmelweis University in 2010.

RESULTS

Acute cardiovascular diseases showed a seasonal variation with the highest occurrence in winter months (p = 0.0001). The daily increase of the events (n ≥ 3) were associated with front movements days (in 62.5% of cases). A significant correlation was found between the intraday temperature difference (p<0.0001), the intraday atmospheric pressure difference (p = 0.0034), the lowest maximum daily temperature (p<0.0001) and the occurrence of acute cardiovascular diseases. During the days with front movements 64% of the patients were older than 66 years of age. Among risk factors, hypertension showed front sensitivity.

CONCLUSIONS

Meteorological parameters are minor risk factors in the occurrence of acute cardiovascular diseases.

Seasonal variation of peripheral blood leukocyte telomere length in Costa Rica: A population-based observational study

OBJECTIVES

Peripheral blood leukocyte telomere length (LTL) is increasingly being used as a biomarker of aging, but its natural variation in human populations is not well understood. Several other biomarkers show seasonal variation, as do several determinants of LTL. We examined whether there was monthly variation in LTL in Costa Rica, a country with strong seasonal differences in precipitation and infection.

METHODS

We examined a longitudinal population-based cohort of 581 Costa Rican adults age 60 and above, from which blood samples were drawn between October 2006 and July 2008. LTL was assayed from these samples using the quantitative PCR method. Multivariate regression models were used to examine correlations between month of blood draw and LTL.

RESULTS

Telomere length from peripheral blood leukocytes varied by as much as 200 base pairs depending on month of blood draw, and this difference is not likely to be due to random variation. A moderate proportion of this association is statistically accounted for by month and region specific average rainfall. We found shorter telomere length associated with greater rainfall.

CONCLUSIONS

There are two possible explanations of our findings. First, there could be relatively rapid month-to-month changes in LTL. This conclusion would have implications for understanding the natural population dynamics of telomere length. Second, there could be seasonal differences in constituent cell populations. This conclusion would suggest that future studies of LTL use methods to account for the potential impact of constituent cell type.

Metabolic syndrome and skin: psoriasis and beyond

Metabolic syndrome (Met S) is a clustering of risk factors comprising of abdominal obesity, dyslipidemia, elevated blood pressure, and abnormal glucose tolerance. The prevalence of Met S has been increasing in the last few years throughout the world. Psoriasis has consistently been associated with Met S as well as its various components. However, the association is no longer limited to psoriasis alone. Various dermatological conditions such as lichen planus, androgenetic alopecia, systemic lupus erythematosus, skin tags, acanthosis nigricans, and even cutaneous malignancies have also been found to be associated with this syndrome. Though chronic inflammation is thought to be the bridging link, the role of oxidative stress and endocrine abnormalities has recently been proposed in bringing them together.

Winter Hypertension: Potential mechanisms

Hypertension exhibits a winter peak and summer trough in countries both north and south of the equator. A variety of explanations have been proposed to account for the seasonal nature of hypertension. It is likely that this reflects seasonal variations in risk factors. Seasonal variations have been demonstrated in a number of risk factors may play essential roles for seasonality of hypertension such as noradrenalin, catecholamine and vasopressin, vitamin D, and serum cholesterol. However, a number of studies have also suggested a direct effect of environmental temperature and physical activity on blood pressure. This paper was design to review the available evidence on seasonal variations in hypertension and possible explanations for them.

Environmental factors and stroke: A selective review

Despite numerous prior stroke risk factor investigations, much remains unknown about the effect of environmental factor changes on stroke incidence and mortality rates. Yet these data might be important for defining a number of measures to prevent stroke and for developing a greater understanding of the origin and incidence trends of stroke in different regions and populations. In this paper we review the current state of knowledge about certain environmental stroke risk factors.

Association of cold ambient temperature and cardiovascular markers

Cardiovascular mortality has been shown to increase in the winter. However, it is unclear whether cold temperature affects indicators known as cardiovascular markers. We evaluated the association between ambient temperature and cardiovascular markers using data collected retrospectively from 55,567 adults who had visited a health check-up clinic between 1995 and 2008. Non-parametric smoothing regressions were fitted to determine the shapes of association between temperature and cardiovascular markers such as blood pressure, lipid profiles, platelet count, and high sensitivity C-reactive protein (hsCRP). Mixed effect model was used to investigate the significance of the relationship between temperature and cardiovascular markers. Decreased ambient temperature was associated with an increase in systolic and diastolic blood pressures, platelet count and serum low density lipoprotein-cholesterol concentration. In contrast, high density lipoprotein-cholesterol level declined with decreasing temperature. The hsCRP level increased with decreasing temperature in the minimum temperatures below 0°C, but revealed a reverse association above. Our study suggests that excess cardiovascular mortality in cold weather might be associated with temperature-related variations of cardiovascular markers.

Human immunodeficiency virus, atherosclerosis and Chlamydophila pneumoniae

Chlamydophila pneumoniae (C. pneumoniae) is an obligate, intracellular bacterium associated with a wide variety of acute and chronic diseases. C. pneumoniae infection is characterized by persistence and immunopathological damage to host target tissues, including the lung. Over the past 20 years, a variety of studies have investigated a possible link between C. pneumoniae infection and atherosclerosis, because of its role in all stages of atherosclerosis, from initial inflammatory lesions to plaque rupture. In the current highly active antiretroviral therapy (HAART) era, many human immunodeficiency virus (HIV)-infected patients are experiencing health problems that accompany the aging process, mainly the risk of cardiovascular disease (CVD). There is renewed interest in a link between atherosclerotic CVD and as yet poorly defined environmental exposures, including infectious agents. On the one hand, the patient with HIV and lipodystrophy caused by HAART and exacerbated by C. pneumoniae infection could be a factor of risk for atherosclerosis. An assessment of the therapy against C. pneumoniae and HAART should always be conducted. It is advisable that HIV-acquired immune deficiency syndrome patients undergo a serological test to determine exposure to C. pneumoniae and to assess treatment options. On the other hand, in patients with a positive serology to C. pneumoniae, an increment of the body mass index has been found; therefore, it is probable that the recurrent infection may play an important role in creating adverse endothelial conditions allowing the infection by C. pneumoniae in its chronic form, to damage the endothelial surface. Vascular studies would be necessary for corroboration.

Interference with RhoA-ROCK signaling mechanism in autoreactive CD4+ T cells enhances the bioavailability of 1,25-dihydroxyvitamin D3 in experimental autoimmune encephalomyelitis

Vitamin D deficiency is a major risk factor for central nervous system (CNS) demyelinating diseases including multiple sclerosis (MS) and its animal model, that of experimental autoimmune encephalomyelitis (EAE). Both vitamin D(3) and 1, 25-dihydroxyviatmin-D(3) (calcitriol) had beneficial effects in EAE/MS. However, the exact cause of vitamin D deficiency in EAE/MS is not clear. Previously, we documented that lovastatin (LOV) provides protection in EAE animals via inhibition of RhoA-ROCK signaling. Herein, we demonstrate that LOV prevents the lowering of circulating 25-hydroxyvitamin-D(3) and 1,25-dihydroxyviatmin-D(3) levels including 1,25-dihydroxyviatmin-D(3) levels in the peripheral lymphoid organs and CNS of treated EAE animals. These effects of LOV were attributed to enhanced expression of vitamin D synthesizing enzyme (1α-hydroxylase) in kidney and the CNS, with corresponding reduction of vitamin D catabolizing enzyme (24-hydorxylase) expression in the CNS of EAE animals via inhibition of RhoA-ROCK signaling. Ex vivo and in vitro studies established that autoreactive Th1/Th17 cells had higher expression of 24-hydroxylase than Th2/T regulatory cells, that was reverted by LOV or ROCK inhibitor. Interestingly, LOV-mediated regulation of vitamin D metabolism had improved vitamin D(3) efficacy to confer protection in EAE animals and that was ascribed to the LOV- and calcitriol-induced immunomodulatory synergy. Together, these data provide evidence that interfering with RhoA-ROCK signaling in autoreactive Th1/Th17 cells can improve vitamin D(3) efficacy in clinical trials of MS and related neurodegenerative disorders.

The skin function: a factor of anti-metabolic syndrome

The body's total antioxidant capacity represents a sum of the antioxidant capacity of various tissues/organs. A decrease in the body's antioxidant capacity may induce oxidative stress and subsequent metabolic syndrome, a clustering of risk factors for type 2 diabetes and cardiovascular disease. The skin, the largest organ of the body, is one of the major components of the body's total antioxidant defense system, primarily through its xenobiotic/drug biotransformation system, reactive oxygen species-scavenging system, and sweat glands- and sebaceous glands-mediated excretion system. Notably, unlike other contributors, the skin contribution is variable, depending on lifestyles and ambient temperature or seasonal variations. Emerging evidence suggests that decreased skin's antioxidant and excretory functions (e.g., due to sedentary lifestyles and low ambient temperature) may increase the risk for metabolic syndrome. This review focuses on the relationship between the variability of skin-mediated detoxification and elimination of exogenous and endogenous toxic substances and the development of metabolic syndrome. The potential role of sebum secretion in lipid and cholesterol homeostasis and its impact on metabolic syndrome, and the association between skin disorders (acanthosis nigricans, acne, and burn) and metabolic syndrome are also discussed.

Cumulative effects of weather on stroke incidence: a multi-community cohort study in Japan

Background

Although seasonal variation in stroke incidence has been reported, it is not known whether year-long exposure to particular meteorological conditions affects the risk of stroke independently of conventional cardiovascular risk factors.

Methods

We conducted a cohort study involving 4849 men and 7529 women residing in 12 communities dispersed throughout Japan. Baseline data were obtained from April 1992 through July 1995. Follow-up was conducted annually to capture first-ever-in-life stroke events. Weather information during the period was also obtained for each community. Multilevel logistic regression analysis was conducted to evaluate the association between stroke incidence and each meteorological parameter adjusted for age, obesity, smoking status, total cholesterol, systolic blood pressure, diabetes, and other meteorological parameters.

Results

Over an average of 10.7 years of follow-up, 229 men and 221 women had stroke events. Among women, high annual rainfall (OR per 1000 mm, 1.46; 95% confidence interval, 1.05–2.03), low average ambient temperature (OR per 1 °C, 0.79; 0.66–0.94), and number of cold days per year (OR per 10 days, 3.37; 1.43–7.97) were associated with increased risk of stroke incidence, independent of conventional risk factors. Among men, number of cold days (OR per 10 days, 1.07; 1.02–1.12) was associated with an increased risk of stroke incidence, but the association became nonsignificant after adjustment for other risk factors. Similar results were obtained for cerebral infarction and cerebral hemorrhage.

Conclusions

Long-term exposure to some meteorological conditions may affect the risk of stroke, particularly in women, independent of conventional risk factors.

Cold-related cardiac mortality in King County, Washington, USA 1980–2001

BACKGROUND

Studies have shown that cardiac deaths increase during the winter months and that death rates can be tightly predicted from temperature rather than other atmospheric phenomena such as barometric pressure, humidity, or pollution.

AIM

The object of this study is to examine the possible relationship between temperature and cardiac death rates in King County, Washington, USA and suggest possible public health measures that can decrease the number of cardiac deaths associated with cold exposure.

SUBJECTS AND METHODS

State death records show that 62,125 total out-of-hospital cardiac-related deaths among persons 55 years and older occurred in King County between 1980 and 2001. We use Poisson regression to examine the association between same-day daily average temperature and death rate after adjusting for seasonal effects.

RESULTS

We identified a significant negative association between daily average temperature and cardiac mortality among persons over 55 years of age. A 5 degrees C increase in temperature was associated with a decrease in death rate by a factor of 0.971 (95% CI: 0.961, 0.982).

CONCLUSION

Cold temperatures may be an important triggering factor in bringing on the onset of life-threatening cardiac events, even in regions with relatively mild winters. Public health efforts stressing cold exposure while out of doors may play a prominent role in encouraging a reduction in cold stress, especially among seniors and those already at higher risk of cardiac death.

Seasonal Variation in Onset of Myocardial Infarction—A 7‐year single‐center study in Italy

Like many other serious acute cardiovascular and cerebrovascular events, acute myocardial infarction (AMI) shows seasonal variation, being most frequent in the winter. We sought to investigate whether age, gender, and hypertension influence this pattern. We studied 4014 (2259 male and 1755 female) consecutive patients with AMI presenting to St. Anna Hospital of Ferrara, Italy between January 1998 and December 2004. Some 1131 (28.2%) of the AMI occurred in persons <65 yrs of age, and 2883 (71.8%) in those > or =65 yrs of age. AMI was over-represented in males (82% in the <65 yr group vs. 56.6% in the > or =65 yr group (chi2=13.99; p<0.001). Hypertension had been previously documented in 964 (24%) of the cases. There were 691 (17.2%) fatal case outcomes; fatal outcomes were significantly higher among the 3054 normotensive (n=614 or 20.1%) than the 964 hypertensive cases (n=77 or 8%; chi2=74.94, p<0.001). AMIs were most frequent in the winter (n=1076 or 26.8% of all the events) and least in the summer (n=924 or 23.0% of all the events; chi2=12.36, p=0.007). The greatest number of AMIs occurred in December (n=379 or 9.44%), and the lowest number in September (n=293 or 7.3%; chi2=11.1, p=0.001). Inferential chronobiological (Cosinor) analysis identified a significant annual pattern in AMI in those > or =65 yrs of age, with a peak between December and February-January for the total sample (p<0.005), January for the sample of males (p=0.014), February for fatal infarctions (p=0.017), and December for non-fatal infarctions (p=0.006). No such temporal variations were detected in any of these categories in those <65 yrs of age. The annual pattern in AMI was also verified by Cosinor analysis in the following hypertensive subgroups: hypertensive males (n=552: January, p=0.014), non-fatal infarctions in hypertensive patients (n=887: January, p=0.018), and elderly normotensives (n=1556: November, p=0.007).

Seasonal variation in lipids in patients following acute coronary syndrome on fixed doses of Pravastatin (40 mg) or Atorvastatin (80 mg) (from the Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis In Myocardial Infarction 22 [PROVE IT-TIMI 22] Study)

Previous studies have shown seasonal variation in lipids. To understand whether this variation exists in patients with acute coronary syndromes receiving statins, we examined data from the PROVE IT-TIMI 22 Study. At baseline, no significant difference in low-density lipoprotein (LDL) cholesterol was observed when stratified by season. However, a statistically significant difference in high-density lipoprotein cholesterol between winter (37 mg/dl) and summer (39 mg/dl) was observed (p <0.001) at baseline. On treatment, median LDL cholesterol was 102 mg/dl in winter versus 96 mg/dl in summer (p <0.001) for the pravastatin group and 68 mg/dl in winter versus 62 mg/dl in summer (p <0.001) for the atorvastatin group. Median high-density lipoprotein cholesterol was 43 mg/dl in summer versus 41 mg/dl in winter in the pravastatin group and 42 mg/dl in summer versus 39 mg/dl in winter in the atorvastatin group (p <0.001). More patients achieved LDL cholesterol <100 mg/dl in summer at 56% versus 47% in winter in the pravastatin group (p <0.001) and 89% versus 87% in winter for the atorvastatin group (p = 0.11). Achievement of LDL cholesterol <70 mg/dl was also higher in summer than winter. In conclusion, this was the first evidence of seasonal variability in cholesterol in patients with acute coronary syndromes treated with statins. This variability affected achievement of National Cholesterol Education Program goals and may affect management decisions based on season of collection.

The impact of exercise training on blood lipids in older adults

Increasing physical activity is often prescribed to improve blood lipids; however, the efficacy of exercise in improving blood lipids in older adults is not clear. The objective of this study was to examine the effects of different exercise modes on blood lipid levels in previously sedentary older adults engaging in a 16-week exercise intervention. One hundred thirty-one subjects (mean age 74.6+/-6 years) were randomly assigned to a resistance training group, aerobic walking group, combined exercise group, or nonexercising control group. Blood lipids were measured at baseline, 8 weeks, and postintervention. Exercise mode did not impact blood lipids. All groups had lower lipid levels over time. Total cholesterol, low- and high-density lipoprotein, and triglycerides were significantly lower. The decrease in all groups, including the controls, may be due to a seasonal effect in older adults that has been documented in younger individuals.

Community-based study on summer-winter differences of component of metabolic syndrome in Kinmen, Taiwan

BACKGROUND

A community-based study was conducted to investigate summer-winter differences of component of metabolic syndrome in Kinmen, Taiwan.

METHODS

A total of 8251 residents aged 40 and over were enrolled in the mass survey in Kinmen. They were investigated while on summer (July and August) and winter vacation (January and February) during 2000-2003. Demographics, physical examination findings, lifestyle variables and biochemical data were collected.

RESULTS

After controlling for age, body mass index, diet, lifestyle and other risk factors for component of metabolic syndrome, there were independent and significant relationships between summer-winter difference and component of metabolic syndrome. Winter season was positively correlated with blood pressure, fasting plasma glucose level, high-density lipoprotein-cholesterol (HDL-C) and waist circumference, but was negatively associated with fasting triglycerides and metabolic syndrome.

CONCLUSIONS

Summer season is positively associated with hypertriglyceridemia, low HDL-C and metabolic syndrome. These findings imply that cross-sectional, experimental and cohort studies of component of metabolic syndrome or metabolic syndrome should take season into account as possible confounding effects.

Effects of intake of a mixture of thiamin, arginine, caffeine, and citric acid on adiposity in healthy subjects with high percent body fat

We assessed the effects of intake of thiamin, arginine, caffeine, and citric acid (TACC) on lipid metabolism in healthy subjects. Thirty-one subjects with high percent body fat (> or = 25.0%) were randomly assigned to a 12-wk intervention with daily intake of TACC-supplemented tea (1.1, 1240, 52, and 540 mg, respectively; n=16) or control tea (n=15). The percent body fat decreased significantly during the intervention in both groups, especially in the TACC group. A percentage decrease in triceps skinfold was significantly greater in the TACC group than in the control group. The decrease in abdominal visceral fat in obese subjects was significantly greater in the TACC group than in the control group. Serum triglyceride was significantly lower during intervention than that during the non-intervention period in the TACC group. These results suggest that TACC may be effective in reducing body fat in obese subjects.

Seasonal variation in total energy expenditure and physical activity in Dutch young adults

OBJECTIVE

The impact of season on energy expenditure and physical activity is not well quantified. This study focused on summer-winter differences in total energy expenditure (TEE) and physical activity.

RESEARCH METHODS AND PROCEDURES

Twenty-five healthy Dutch young adults, living in an urban environment, were measured in the summer season and the winter season. TEE was measured using doubly labeled water, and sleeping metabolic rate (SMR) was measured during an overnight stay in a respiration chamber. Subsequently, the physical activity level (PAL = TEE/SMR) and activity-related energy expenditure [(0.9 x TEE) - SMR] were calculated. Maximal mechanical power (Wmax) was determined with an incremental test on a cycle ergometer. Body composition was measured with hydrostatic weighing and deuterium dilution using Siri's three-compartment model.

RESULTS

There was no difference in TEE between seasons. PAL was higher in summer than in winter (1.87 +/- 0.22 vs. 1.76 +/- 0.18; p < 0.001), and the difference was higher for men than for women (0.20 +/- 0.14 vs. 0.05 +/- 0.16; p = 0.04). The difference in PAL between seasons was dependent on the initial activity level. There was a strong linear relation (R2 = 0.48) between PAL and physical fitness (Wmax/fat-free mass), but Wmax/fat-free mass did not change between seasons in response to the lower PAL in winter.

DISCUSSION

The extent of the changes in PAL is of physiological significance, and seasonality in physical activity should be taken into account when studying physical activity patterns or relationships between physical activity and health.

Correlates of plasma homocysteine, cysteine and cysteinyl-glycine in respondents in the British National Diet and Nutrition Survey of young people aged 4-18 years, and a comparison with the survey of people aged 65 years and over

Plasma total homocysteine (tHcy), cysteine and cysteinyl-glycine were measured in a representative sample of 922 young people aged 4-18 years, participating in the National Diet and Nutrition Survey in mainland Britain in 1997. Both tHcy and cysteine increased markedly with age; cysteinyl-glycine less so. Neither tHcy nor cysteine differed between genders; cysteinyl-glycine was higher in males. tHcy concentrations were lowest in the winter; cysteine and cysteinyl-glycine varied only slightly with season. In respondents aged >15 years, tHcy was higher in smokers, but in respondents aged 7-11 years, tHcy was higher in those whose mothers smoked. tHcy was inversely correlated with serum folate, serum vitamin B12 and vitamin B6 status, but neither cysteine nor cysteinyl-glycine shared these relationships. The relationships between tHcy and B-vitamin status indices ran parallel with those of the 65 years and over survey, but at much lower tHcy concentrations for any given B-vitamin concentration. Age-adjusted tHcy was not correlated with anthropometric indices, blood pressure, haematology, plasma creatinine, urea or cholesterol, but was directly correlated with fasting triacylglycerol. We conclude that disease-risk indices, like tHcy and perhaps cysteine, if established during early life, may be modulated by diet and lifestyle, thereby providing an opportunity for public health intervention.

Seasonal variation in cause-specific mortality: are there high-risk groups? 25-year follow-up of civil servants from the first Whitehall study

OBJECTIVES

To determine the seasonal effect on all-cause and cause-specific mortality and to identify high-risk groups.

METHODS

A 25-year follow-up of 19,019 male civil servants aged 40-69 years.

RESULTS

All-cause mortality was seasonal (ratio of highest mortality rate during winter versus lowest rate during summer 1.22, 95% CI : 1.1-1.3), largely due to the seasonal nature of ischaemic heart disease. Participants at high risk based on age, employment grade, blood pressure, cholesterol, forced expiratory volume, smoking and diabetes did not have higher seasonal mortality, although participants with ischaemic heart disease at baseline did have a higher seasonality effect (1.38, 95% CI : 1.2-1.6) than those without (1.18, 95% CI : 1.1-1.3) (P = 0.03).

CONCLUSIONS

Seasonal mortality differences were greater among those with prevalent ischaemic heart disease and at older ages, but were not greater in individuals of lower socioeconomic status or with a high multivariate risk score. Since seasonal differences showed no evidence of declining over time, elucidating their causes and preventive strategies remains a public health challenge.

Influence of dietary intake and physical activity on annual rhythm of human blood cholesterol concentrations

Seasonal variation in the plasma total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) have been repeatedly reported, with contradictory results regarding the pattern of seasonal variation of these parameters. Furthermore, it is still not well established whether the variation is due to changes in the nutrition or changes in physical activity depending on the season. The aim of this study was therefore to determine plasma TC and HDL-C in different groups of healthy participants: 19 vegetarians with a constant diet independent of the season, 14 athletes with almost constant physical activity over the year, and 114 controls in the age groups 20-26 years (mean age 24 + 1.5 years) and 40-48 years (mean age 44.3 + 2.1 years). Over 2 years, blood samples were collected every 2-3 months and were analyzed for plasma TC and HDL-C. At all visits, body mass index (BMI) and waist-to-hip ratio (WHR) were calculated, and nutrition and physical activity profiles were obtained. The seasonal model was calculated using object-oriented software for the analysis of longitudinal data in S (OSWALD); multiple regression analysis was used to determine the influence of age, gender, diet, and physical activity on seasonal changes of the lipid parameters. In all groups, we found an annual rhythm of the plasma TC and HDL-C concentrations, which can be mathematically described by a sine curve with a maximum in winter and a minimum in summer. This rhythm was independent of the age, gender, BMI, diet, or physical activity. The observed seasonal differences between the maximum and the minimum were about 5%-10% for TC and about 5%-8% for HDL-C concentration. These differences were greater than the determined circadian (TC 3.5%, HDL-C 4%) and day-to-day changes for TC and HDL-C (coefficient of variation <5% for both). In conclusion, annual rhythm of TC and HDL-C is not primarily induced by seasonal differences in dietary intake or physical activity. Therefore, the annual rhythm in cholesterol levels is most likely determined by endogenous factors or factors directly related to seasonal changes in the environment.

Seasonal variation in lipoprotein lipase and plasma lipids in physically active, normal weight humans

Adipose tissue lipoprotein lipase (ATLPL) provides free fatty acids (FFA) for storage in adipocytes, whereas in skeletal muscle LPL (SMLPL) provides FFA for oxidation. In hibernating animals, the level of SMLPL is relatively higher in summer than winter (promoting fat oxidation), whereas the opposite is seen with ATLPL. A patient-controlled study was designed to determine whether such seasonal variation occurs in normal weight humans. Eighteen subjects were studied in the summer and winter. After 2 days of a standardized diet, they underwent muscle and adipose biopsies for LPL activity, assessment of fitness by VO2 max, and determination of body composition by hydrostatic weighing. The percentages of body fat, body mass index, VO2 max, insulin, glucose, FFA, glycerol, and leptin were not affected by the season. Total cholesterol was higher in the winter than in the summer (157 +/- 5.5 vs. 148 +/- 4.2 mg/dL respectively; P = 0.03). The ATLPL activity was also higher in the winter than in the summer (4.4 +/- 0.8 vs. 2.3 +/- 0.6 nmol FFA/10(6) cells-min; P = 0.04). SMLPL activity trended to be higher in the winter than in the summer (1.9 +/- 0.5 vs. 1.0 +/- 0.1 nmol FFA/g x min; P = 0.06). In summary, ATLPL is seasonally regulated. It appears that SMLPL is similarly regulated by season. For physically active lean subjects, this increase in SMLPL may be a compensatory mechanism to help protect from seasonal weight gain.

A population-based study of the associations of stroke occurrence with weather parameters in Siberia, Russia (1982-92)

Previous studies have established a seasonal variation in stroke occurrence, but none have assessed the influence of inclement weather conditions on stroke incidence in a general population of Russia. We performed a stroke population-based study in the Oktiabrsky District of Novosibirsk, Siberia, Russia. Included in the analysis were 1929 patients with their first occurrence of ischemic stroke (IS), 215 patients with their first occurrence of intracerebral hemorrhage (ICH) and 64 patients with their first occurrence of subarachnoid hemorrhage (SAH): all patients were aged between 25 and 74 years. The cumulative daily occurrence of total strokes and stroke subtypes was evaluated in relation to aggregated daily mean values of ambient temperature, relative humidity and air pressure by means of Poisson regression analysis to estimate the rate ratio (RR) with corresponding confidence interval (CI) and to identify the weather parameters of most importance. In a multivariate analysis, with adjustment for the effects of season, solar and geomagnetic activity, and age of the patients, low ambient temperature (RR 1.32; 95% CI 1.05-1.66) and mean value of air pressure (RR 0.986; 95% CI 0.972-0.999) were important predictors of IS occurrence, while mild ambient temperature (RR 1.52; 95% CI 1. 04-2.22) was an important predictor of ICH occurrence. No relationship between SAH occurrence and any one of the weather parameters studied was revealed. There was no interaction between any meteorological variables that was statistically significant. Inclement weather conditions are associated with the occurrence of IS and ICH in Siberia, Russia. Among the meteorological parameters studied, low ambient temperature and mean air pressure are the most important predictors of IS occurrence, whereas the occurrence of ICH is associated with mild ambient temperature. There is no association between any one of the weather parameters studied and the occurrence of SAH.

Chlamydia pneumoniae antibodies are associated with an atherogenic lipid profile

OBJECTIVE

To determine, within a representative population group of men and women, whether alteration of the lipid profile might underlie the reported association between Chlamydia pneumoniae and ischaemic heart disease.

DESIGN AND SETTING

Cross sectional survey in an area with a high incidence of ischaemic heart disease.

SUBJECTS

400 randomly selected participants in the World Health Organisation MONICA project's third population survey in Northern Ireland.

MAIN OUTCOME MEASURES

Stored sera were examined by microimmunofluorescence for IgG antibodies to C pneumoniae at a dilution of 1 in 64. Mean total and high density lipoprotein (HDL) cholesterol were compared between seropositive and seronegative individuals with adjustment for age, measures of socioeconomic status, smoking habit, alcohol consumption, body mass index, and the season during which blood had been taken.

RESULTS

In seropositive men, adjusted mean serum total cholesterol and HDL cholesterol were 0.5 mmol/l (9.2%) higher and 0.11 mmol/l (9.3%) lower, respectively, than in seronegative men. Differences in women did not achieve statistical significance, but both total cholesterol and HDL cholesterol were higher (3.6% and 5.8%, respectively) in seropositive than in seronegative individuals.

CONCLUSIONS

There is serological evidence that C pneumoniae infection is associated with an atherogenic lipid profile in men. Altered lipid levels may underlie the association between C pneumoniae and ischaemic heart disease.

Variability and determinants of total homocysteine concentrations in plasma in an elderly population

The variability of plasma total homocysteine (tHcy) was examined in 96 individuals over a 1-yr period. Blood tHcy concentrations varied from 7.1 μmol/L in the bottom quintile to 14.5 μmol/L in the top quintile. The mean tHcy was 10.4 μmol/L, the between-person SD was 2.5 μmol/L, and the within-person SD was 0.93 μmol/L. There was little seasonal variation, and the reliability coefficient was 0.88. Mean tHcy concentrations were inversely related to mean plasma folate (r = −0.36) and vitamin B12 (r = −0.35) concentrations. Median tHcy concentrations were ∼1 μmol/L higher in men than in women and in older (70 to 74 years) than in younger (65 to 69 years) individuals and higher in those with the TT and CT genotypes for the methylenetetrahydrofolate reductase polymorphism than in those with the CC genotype (10.7 and 10.6 vs 9.6 μmol/L). Epidemiological studies based on single tHcy measurements may underestimate the magnitude of any risk associations with disease by 10–15%.

Seasonal variation in the occurrence of ischemic stroke and subarachnoid hemorrhage in Siberia, Russia. A population-based study

Epidemiological studies on the relationship between stroke occurrence and the seasons in different countries produced inconsistent results and little is known about these associations in a general population. We report a population-based study of 214 patients with first-ever ischemic stroke (IS, data for 1992) and 64 patients with first-ever subarachnoid hemorrhage (SAH) registered in the 25-74 years old population of Oktiabrsky District of Novosibirsk, Russia in 1982-92. IS and SAH incidence in four seasons (winter, spring, summer, autumn) was evaluated by means of a chi-square test. Poisson regression analysis was used to compute the rate ratios (RRs) and corresponding confidence intervals (CIs) for the occurrence of IS and SAH in winter, spring, and autumn compared with summer. Seasonal variations in the occurrence of IS were significant for the group of young men (25-64 years) and the group of older women (65-74 years) only. The age and sex adjusted RR of the occurrence of IS in winter was 49% greater than in summer (95%CI 1-119%). When men and women were analyzed separately and the rates were adjusted for age, a significantly higher risk of IS was found only in men (RR = 2.48; 95% CI 1.27-4.83) in spring compared with summer. No seasonality was observed for the occurrence of SAH in both men and women. Our findings indicate that there is a significantly greater incidence of ischemic stroke during winter in Siberia, Russia, whereas the incidence of SAH does not show a seasonal variation.

Chronobiological patterns of onset of acute cerebrovascular diseases

There is a considerable amount of data indicating that several major unfavorable cerebrovascular events are not randomly distributed over time, but show a peculiar distribution along the day, the week, and the months of the year. The authors review the available evidence on the chronobiological (circadian, weekly, and seasonal) patterns of onset of acute cerebrovascular diseases and variations in their possible triggering mechanisms. The existence of a peculiar chronobiological pattern in the onset of acute cerebrovascular disease, characterized by both circadian (morning and evening occurrence), circaseptan (last and first days of the week), and circannual (especially in winter) is confirmed, although differences depending on biological (gender, age), pathological (diabetes, hypertension, smoke, alcohol), cultural, social, and environmental factors exist. A deeper knowledge of the underlying pathophysiologic mechanisms could provide more effective insights for both preventive strategies and optimization of therapeutic approach.

Seasonal variations of rheological and hemostatic parameters and acute-phase reactants in young, healthy subjects

The incidence of cardiovascular diseases is increased in winter months. Recent studies have shown seasonal changes in plasma viscosity, fibrinogen, and factor VII activity with elevated levels during winter. An increase in these factors generates a "hypercoagulable state," which may lead to a rise in cardiovascular morbidity and mortality. It has been suggested that an increase in upper respiratory infections might be the underlying cause for the raised acute-phase reactants, in particular fibrinogen, during the winter season. We investigated seasonal variations of 26 parameters, determining blood rheology and hemostasis in 16 healthy volunteers (8 men and 8 women) aged 20 to 41 years. They were seen at monthly intervals over a period of 1 year. Seasonal variation with peak fitted values in the winter months was found for plasma viscosity (P < .001 for the seasonal difference), red blood cell deformability (P < .001), whole blood viscosity (P < .001), hemoglobin (P < .001), hematocrit (P < .001), mean corpuscular volume (P = .001), platelet count (P = .01), alpha 1-glycoprotein (P < .001), fibrinogen (measured by immunonephelometry; P < .001), plasminogen activator inhibitor-1 (P = .002), LDL cholesterol (P = .003), and triglyceride levels (P < .001). HDL cholesterol (P < .001) and cortisol (P = .001) showed inverse seasonal patterns, with a maximum during summertime. No statistically significant seasonal variations were seen for red blood cell aggregation, complement factor C4, total cholesterol, ceruloplasmin, haptoglobin, white blood cell count, and plasminogen. These data do not support the hypothesis that increased morbidity and mortality from cardiovascular diseases during winter may be mainly attributable to increased synthesis of acute-phase proteins due to infections. The cause for the seasonal variations in rheological and hemostatic parameters remains unclear and should be studied in more detail.

Temperature extremes and mortality from coronary heart disease and cerebral infarction in elderly Chinese

We studied the relation between outdoor temperature and mortality rates from cardiovascular disease in Taiwan from 1981 to 1991. In 11 years, there were 30,085, 21,750, and 39,818 deaths from coronary artery disease, cerebral infarction, and cerebral haemorrhage, respectively, among 7.6 million residents aged 25 and over in selected areas where climate was recorded. A temperature-mortality relation was especially apparent in the elderly. A U-shaped relation was observed between temperature and mortality from coronary artery disease and cerebral infarction. The range corresponding to least deaths from coronary artery disease (26-29 degrees C) and cerebral infarction (27-29 degrees C) was higher than that in countries with colder climates. In the elderly, the risk of cerebral infarction at 32 degrees C was 66% higher than that at 27-29 degrees C; the risk increased by 3.0% per 1 degree C reduction from 27-29 degrees C. The risk of coronary artery disease at 32 degrees C was 22% higher than that at 26-29 degrees C; below 26-29 degrees C, the risk increased by 2.8% per 1 degree C reduction. Mortality from cerebral haemorrhage decreased with increasing temperature at a rate of 3.3% per 1 degree C. These results imply a pathophysiological difference between thromboembolic and haemorrhagic cardiovascular diseases. Poor thermoregulation in older people may precipitate cardiovascular disease events.

Seasonal variations of plasma fibrinogen and factor VII activity in the elderly: winter infections and death from cardiovascular disease

There are approximately 20,000 excess deaths from cardiovascular disease each winter in England and Wales. The reasons for the excess have not been fully elucidated. For one year, we studied 96 men and women aged 65-74 living in their own homes in order to examine seasonal variation in plasma fibrinogen and factor VII clotting activity (FVIIc), and to investigate relationships with infection and other cardiovascular-disease risk factors. Both fibrinogen and FVIIc plasma values were greater in winter with estimated winter-summer differences (confidence intervals) of 0.13 (0.05-0.20) g/L for fibrinogen and 4.2 (1.2-7.1)% of standard for FVIIc. These differences could account for 15% and 9% increases in ischaemic heart disease risk in winter respectively. After adjustment for confounding by season, fibrinogen was strongly related to neutrophil count (p < 0.0001), C-reactive protein (p < 0.0001), alpha 1-antichymotrypsin (p < 0.0001), and self-reported cough (p < 0.0001) and coryza (p = 0.0004), but not to ambient temperature. Therefore, we suggest that seasonal variation in fibrinogen might be induced by winter respiratory infections via activation of the acute phase response. Seasonal variations in the cardiovascular risk factors fibrinogen and FVIIc provide further possible explanations for the marked seasonal variation in death from ischaemic heart disease and stroke in the elderly.