Seasonal variation of risk factors for cardiovascular disease and diet in older adults.

We have already published much of our data on the seasonal variation of cardiovascular disease risk factors in a cohort of 65-74 year old men and women living in Cambridge, UK. In this paper we give a concise overview of our findings and include previously unpublished data relating to diet. Seasonal variation in intake of fat, copper, beta-carotene and vitamins A, C and E were all found with increased fat, beta-carotene and vitamin A intakes in autumn and winter while vitamin C and E intakes peaked in summer. Seasonal variation of vitamin C intake and serum ascorbate concentrations were particularly pronounced. We postulate that low vitamin C levels in winter could be associated raised plasma fibrinogen and plasminogen activator-1 (PAI-1) concentrations and therefore with increased cardiovascular risk.

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 micromol/L in the bottom quintile to 14.5 micromol/L in the top quintile. The mean tHcy was 10.4 micromol/L, the between-person SD was 2.5 micromol/L, and the within-person SD was 0.93 micromol/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 approximately 1 micromol/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 micromol/L). Epidemiological studies based on single tHcy measurements may underestimate the magnitude of any risk associations with disease by 10-15%.

Plasminogen activator inhibitor-1, the acute phase response and vitamin C.

Epidemiologial studies suggest that elevated plasma plasminogen activator inhibitor-1 (PAI-1) activity is associated with ischaemic heart disease. Based on our earlier work suggesting a link between plasma fibrinogen, infection and low vitamin C status, we sought to determine whether similar relationships existed for PAI-1 activity. We performed a longitudinal study of cardiovascular disease risk factors in 96 volunteers aged 65-74 years, living in the community in Cambridge. Each subject was visited at home 7 times over a 14 month period. Plasma PAI-1 activity, serum ascorbate, markers of the acute phase response, serum lipids and other cardiovascular disease risk factors were measured on each occasion. In a multiple regression analysis, the three significant predictors of PAI-1 activity were body mass index (P = 0.0001), blood neutrophil count (P = 0.03) and, inversely, serum ascorbate (P = 0.003). The inverse relationship between PAI-1 activity and serum ascorbate persisted even when vitamin C supplement takers or smokers were excluded from the analysis. Serum ascorbate was strongly related to estimated dietary intake of vitamin C (P < 0.0001). Low serum ascorbate is associated with high PAI-1 activity which is, in turn, associated with increased ischaemic heart disease risk. We hypothesise that activation of the acute phase response by infection could increase PAI-1 activity and, consequently, also increase the risk of coronary artery thrombosis. Furthermore, we suggest that vitamin C could attenuate this response.

Interrelation of vitamin C, infection, haemostatic factors, and cardiovascular disease.

OBJECTIVE: To examine the hypothesis that the increase in fibrinogen concentration and respiratory infections in winter is related to seasonal variations in vitamin C status (assessed with serum ascorbate concentration). DESIGN: Longitudinal study of individuals seen at intervals of two months over one year. SETTING: Cambridge. SUBJECTS: 96 men and women aged 65-74 years living in their own homes. MAIN OUTCOME MEASURES: Haemostatic factors fibrinogen and factor VIIC; acute phase proteins; respiratory symptoms; respiratory function. RESULTS: Mean dietary intake of vitamin C varied from about 65 mg/24 h in winter to 90 mg/24 h in summer; mean serum ascorbate concentration ranged from 50 mumol/l in winter to 60 mumol/l in summer. Serum ascorbate concentration was strongly inversely related to haemostatic factors fibrinogen and factor VIIC as well as to acute phase proteins but not to self reported respiratory symptoms or neutrophil count. Serum ascorbate concentration was also related positively to forced expiratory volume in one second. An increase in dietary vitamin C of 60 mg daily (about one orange) was associated with a decrease in fibrinogen concentrations of 0.15 g/l, equivalent (according to prospective studies) to a decline of approximately 10% in risk of ischaemic heart disease. CONCLUSION: High intake of vitamin C has been suggested as being protective both for respiratory infection and for cardiovascular disease. These findings support the hypothesis that vitamin C may protect against cardiovascular disease through an effect on haemostatic factors at least partly through the response to infection; this may have implications both for our understanding of the pathogenetic mechanisms in respiratory and cardiovascular disease and for the prevention of such conditions.

Seasonal variation in 25-hydroxyvitamin D and parathyroid hormone concentrations in healthy elderly people.

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 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.

Seasonal variation of blood pressure and its relationship to ambient temperature in an elderly population.

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. RESULTS: Both systolic (SBP) and diastolic blood pressure (DBP) were greatest during the winter across the whole distribution of blood pressure. There was a fourfold increase in the proportion of subjects with blood pressures > 160/90 mmHg in winter compared with in summer. Regression analysis revealed highly significant seasonal differences in both SBP and DBP. After adjustment for confounding seasonal effects, a 1 degree C decrease in living-room temperature was associated with rises of 1.3 mmHg in SBP and 0.6 mmHg in DBP. CONCLUSIONS: Seasonal variation of blood pressure is heightened in older adults and may partly explain the greater cardiovascular disease mortality of elderly subjects during the winter. The blood pressures of elderly people may be inversely related to the ambient temperature. The public health implications of these findings deserve further investigation.

Seasonal variation of serum lipids in an elderly population.

We investigated seasonal variation in serum lipids in 96 volunteers aged 65-74 years who were studied at 2-monthly intervals for one year. Periodic regression analysis revealed highly significant seasonal variation in serum total cholesterol and high-density lipoprotein (HDL) cholesterol. Peak levels for both occurred in winter with corresponding summer troughs. The seasonal difference for total cholesterol was 0.32 mmol/l (95% CI 0.23-0.41, p < 0.0001) and that for HDL cholesterol 0.16 mmol/l (95% CI 0.12-0.19, p < 0.0001). Low-density lipoprotein (LDL) cholesterol was highest in winter in men only (seasonal difference 0.27 mmol/l, 95% CI 0.15-0.39, p < 0.0001), and triglycerides were significantly greater in late winter for women only (seasonal difference 0.22 mmol/l, 95% CI 0.09-0.35, p = 0.002). The timing of seasonal variation in total cholesterol and triglycerides would be consistent with a role in the seasonal variation in vascular deaths, but our finding of a relatively high HDL: total cholesterol ratio in winter makes this less likely.

Assessment of cardiotocographs.

In recent years advances in medical electronic equipment for monitoring, diagnosis and treatment of patients have led to a large increase in the number and variety of instrumentation available to the medical profession. There is a considerable amount of duplication of equipment and in the absence of readily available information buyers are unlikely to make informed decisions about the ideal instrument for their particular circumstances. One method of increasing the users' awareness is a comparative, independent assessment of equipment, with the results disseminated to the interested parties. This paper describes the essential qualities of cardiotocographs: how they are assessed as part of the UK Department of Health's evaluation programme and the measures to inform users of the latest evaluation information.

Factors associated with hypothermia in patients admitted to a group of inner city hospitals.

In a case-control study of factors contributing to hypothermia all fourteen patients (mean age 80 years) admitted to hospital with hypothermia after being found ill indoors also had some other serious illness. They were more likely than control patients to have been alone when taken ill (93 vs 39% of controls), to live alone (86 vs 43%), and to have been found on the floor (79 vs 14%). They were less likely to have been wearing more than indoor clothing (0 vs 50%), or to have had heating on when found (50 vs 89%), but 93% of patients in both groups had heating available. Healthy young adult volunteers who lay immobile on the ground in air at 5 degrees C lightly clothed cooled progressively by 0.57 degrees C (SD 0.32) (rectal T degrees) in 90 min despite doubling of metabolic rate. With better insulation in bed, core temperature stabilised within 90 min, and when they were in an armchair it fell slowly, with no increase in metabolic rate in either case. The findings suggest that hypothermia indoors resulted largely from collapse due to illness when the patient was alone lightly clothed and not in bed. Eight hypothermic patients found outside (in December and January) were younger (mean age 60 years) than the fourteen found indoors; six of these were chronic alcoholics or acutely intoxicated, and six lacked, or had wandered from, a fixed home.

Ranitidine prophylaxis before anaesthesia in early pregnancy.

Forty patients presenting for vaginal termination of pregnancy, divided randomly into four groups, received either no medication, sodium citrate 30 ml orally, ranitidine 150 mg orally or ranitidine 50 mg intravenously. During the procedure, gastric contents were removed by orogastric tube for volume and pH measurements. Ranitidine, orally and intravenously, significantly increased gastric pH and reduced gastric volume. In the control group only one pH was greater than 2.5. Sodium citrate raised the pH above 2.5 in 6 out of 10 patients. Fasting patients in the first months of pregnancy may be at risk of developing Mendelson's syndrome. Ranitidine is very effective in increasing gastric pH and at the same time reducing gastric volume in such patients.

PIP: 40 patients presenting for vaginal termination of pregnancy, divided randomly into 4 groups, received either no medication, sodium citrate 30 ml orally, ranitidine 150 mg orally, or ranitidine 50 mg intravenously. During the procedure, gastric contents were removed by orogastric tube for volume and pH measurements. Ranitidine, both orally and intravenously, significantly increased gastric pH and reduced gastric volume. In the control group, only 1 pH was greater than 2.5. Sodium citrate increased the pH above 2.5 in 6 or 10 patients. Fasting patients in the 1st months of pregnancy may be at risk of developing Mendelson's syndrome. Ranitidine is very effective in increasing gastric pH and at the same time reducing gastric volume in such patients.