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F J Kok

Publications and source records attributed to F J Kok.

At least 109 records · Page 6Linked to original sources
PubMed1992

Increased cytogenetic damage in smokers deficient in glutathione S-transferase isozyme mu.

Reduced expression of the mu-isozyme of glutathione S-transferase (GST; EC 2.5.1.18) has been associated with increased lung cancer risk. We studied the association between GST-mu expression and DNA damage as measured by sister chromatid exchanges (SCE) in healthy male smokers. SCE levels were higher in the 71 GST-mu-deficient smokers compared to the 83 non-deficient smokers (5.24 versus 4.97 SCE/lymphocyte; P = 0.09). In smokers having high plasma cotinine levels (greater than median of 315 ng/ml), this mu-related difference was more pronounced (5.50 versus 4.97; P = 0.01), whereas it was absent in smokers having low cotinine levels (4.95 versus 4.97; P = 0.92). Increased cytogenetic damage in GST-mu-deficient heavy smokers may thus explain the association between GST-mu expression and lung cancer.

Adult↗
PubMed1992

Calcium intake and 28-year cardiovascular and coronary heart disease mortality in Dutch civil servants.

Data obtained from a general health examination in 1953-1954 of 2605 middle-aged Dutch civil servants were analysed to investigate the relation between dietary calcium and cardiovascular (CVD) and coronary heart disease (CHD) mortality. Calcium intake was assessed at baseline by a 1-week food frequency recall. Multivariate adjusted odds ratios (OR) were calculated using the highest quintile of calcium intake as the reference. No statistically significant associations were observed for low calcium intake in 15 and 28 years of follow-up in both men and women. For men, multivariate adjusted OR for the lowest quintile of calcium intake were 1.3 (95% confidence interval (CI): 0.8-1.9) and 0.9 (95% CI: 0.6-1.6) for 28-year CVD and CHD mortality, respectively. For women, corresponding OR were 1.1 (95% CI: 0.6-2.0) and 1.1 (95% CI: 0.5-2.5). Although an inverse association between calcium intake and CVD and CHD mortality, possibly mediated by blood pressure, might be hypothesized, no clear association was observed. Because dietary patterns in the 1950s were quite stable, and major calcium sources were addressed, misclassification of calcium intake may not be fully responsible for this finding.

Aged↗
PubMed1992

Habitual dietary calcium intake and blood pressure change around the menopause: a longitudinal study.

In a 10-year follow-up study, blood pressure and dietary intake were measured annually in 167 healthy perimenopausal normotensive women. Their initial ages ranged between 49 and 56 years and habitual calcium intake between 560 and 2580 mg/day (mean 1110 mg/day); they lived in the mixed rural/industrial community of Ede, the Netherlands. The longitudinal design provided an opportunity to study the 'natural history' of blood pressure and the effect of dietary calcium during and after the period of ovarian failure. For data analysis, person-time experience was divided into three menopausal periods. Based on years relative to menopause three menopausal cohorts were created starting 2 years before, 2 years after and 6 years after menopause, each was followed for 4 years. Changes in systolic (SBP) and diastolic blood pressure (DBP) during the menopausal periods were adjusted for change in body mass index and other relevant variables in multiple regression analysis. An average decline in SBP of 6 mm Hg was observed in the period of 2 years before menopause to 6 years after menopause, and an increase of almost 5 mm Hg in the period between 6 and 10 years after menopause. A significant change in DBP was not observed. Neither changes in, nor the absolute level of, calcium intake showed any relevant association with blood pressure change. Ovarian failure seems to reverse temporarily the increase in blood pressure due to aging. The results do not suggest that a habitual calcium intake exceeding 800-1000 mg/day (the current Recommended Daily Allowance for adults) is effective in preventing hypertension during the peri- and postmenopausal period.

Blood Pressure↗
PubMed1992

Clustering of dietary variables and other lifestyle factors (Dutch Nutritional Surveillance System).

STUDY OBJECTIVE: The aim was to investigate whether dietary factors cluster in a favourable or unfavourable way and to characterise the groups identified by lifestyle and sociodemographic variables. DESIGN AND SETTING: This cross sectional study was based on data of the 1987-1988 Dutch national food consumption survey (DNFCS), obtained from a panel by a stratified probability sample of the non-institutionalised Dutch population. PARTICIPANTS: 3781 adults (1802 males and 1979 females) of the DNFCS, aged 19 to 85 years, were studied. MEASUREMENTS AND MAIN RESULTS: To estimate dietary intake two day food records were used. Lifestyle factors were collected by structured questionnaire and sociodemographic variables were available from panel information. Cluster analysis was used to classify subjects into groups based on similarities in dietary variables. Subsequently, these groups were characterised by sociodemographic and lifestyle factors as well as by the consumption of food groups. Eight clusters were found. In comparison with the guidelines, the dietary quality in four clusters was poor. The cluster with the poorest dietary intake (high intake of fat, cholesterol, and alcohol; low intake of dietary fibre) showed on average a high consumption of animal products (except milk), fats and oils, snacks, and alcoholic beverages, and a low consumption of fruit, potatoes, vegetables, and sugar rich products. Smoking, body mass index, dietary regimen on own initiative, hours of sleep, gender, age, socioeconomic status, and day of the week were found to discriminate among the clusters. CONCLUSIONS: Cluster analysis resulted in substantial differences in mean nutrient intake and seems useful for dietary risk group identification. Undesirable lifestyle habits were interrelated in some clusters, but an exclusive lifestyle for health risk has not been found.

Adolescent↗
PubMed1992

Hematocrit and cardiovascular risk factors among elderly men and women (Dutch Nutrition Surveillance System).

Changes in whole blood viscosity associated with hematocrit could be one of the pathways along which the cardiovascular disease (CVD) risk factors affect these diseases. Therefore, we studied in a nationwide survey comprising 514 apparently healthy Dutch elderly men and women aged 65-79 the possibility of any association between hematocrit and CVD risk factors (tobacco smoking, serum cholesterol, body mass index and blood pressure). Among men, diastolic blood pressure and total serum cholesterol were positively associated with hematocrit in both bivariate and multivariate regression analysis, whereas positive associations of hematocrit with body mass index and smoking were only significant (p < 0.05) in bivariate analysis. Among women, hematocrit was positively associated with body mass index and smoking. Except for smoking, which was associated with the mean corpuscular volume of the erythrocytes, hematocrit was positively correlated with hemoglobin and the number of erythrocytes. It is concluded that hemorrheological aspects should be considered when studying CVD among elderly people.

Aged↗
PubMed1992

Supplementation with vitamin E but not beta-carotene in vivo protects low density lipoprotein from lipid peroxidation in vitro. Effect of cigarette smoking.

Several lines of evidence suggest that oxidatively modified low density lipoprotein (LDL) is atherogenic and that antioxidants may protect LDL against oxidation. In addition, cigarette smoking is known to induce oxidant stress. We have examined the effect of ingestion of the antioxidants D,L-alpha-tocopherol (vitamin E) and beta-carotene and of smoking on the resistance of LDL against copper-mediated oxidation. Six healthy nonsmoking volunteers ingested 1,000 IU/day D,L-alpha-tocopherol acetate for 7 days. After vitamin E ingestion concentrations of alpha-tocopherol in plasma and LDL increased 3.0- and 2.4-fold, respectively. Simultaneously, the oxidation resistance of LDL was elevated significantly (+41%), and the rate of oxidation was decreased significantly (-19%). The increase in alpha-tocopherol content of LDL and the increase in resistance time were highly correlated (rs = 0.89, p = 0.014). Eight weeks after termination of the vitamin E intake, alpha-tocopherol concentrations in plasma and LDL and oxidation resistance of LDL had returned to baseline values. In smokers (n = 46), plasma levels of vitamin C (-26%) and concentrations of beta-carotene (-44%, -43%) and total carotenoids (-23%, -29%) in plasma and LDL, respectively, were significantly lower compared with nonsmokers (n = 23). No differences were found in alpha-tocopherol content of LDL and the susceptibility of LDL to lipid peroxidation in both groups. Supplementation of a group of smokers in a 14-week randomized, double-blind, placebo-controlled intervention trial with beta-carotene resulted in a 16.6- and 5.0-fold increase of LDL beta-carotene and total carotenoid content, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Combination of dietary factors in relation to breast-cancer occurrence.

Combinations of dietary factors were studied in relation to breast-cancer occurrence among 133 breast cancer cases and 289 population controls in The Netherlands. Dietary factors were classified according to their possible mechanism of action, i.e., relating either to the intestinal microflora (total fat, fiber, fermented milk products) or to the anti-oxidant hypothesis (beta-carotene, selenium and polyunsaturated fatty acids). From 6 interactions evaluated, the combination of high fiber intake and high intake of fermented milk products was the only one suggesting synergistic protection (age-and-fat-adjusted OR for interaction = 0.48, 95% confidence interval (CI) = 0.21 - 1.13). In order to estimate the extent to which the above dietary factors together might be related to breast cancer, subjects with a supposedly favorable dietary pattern (low fat intake, high fiber intake, high intake of fermented milk products; high intake of beta-carotene and selenium, low intake of polyunsaturated fatty acids) were compared with subjects with an unfavorable dietary pattern. This resulted in an age-adjusted odds ratio of 0.40 (95% CI = 0.14 - 1.15), which was largely attributable to the combination of low intake of fat and high intake of fermented milk products and fiber (age-adjusted OR = 0.33, 95% CI = 0.15 - 0.73). The other factors did not appreciably affect the odds ratio. These analyses show in a quantitative way that a dietary pattern which combines low intake of fat and high intake of fiber and fermented milk products might provide substantial protection against breast cancer.

Adult↗
PubMed1991

Do antioxidants and polyunsaturated fatty acids have a combined association with coronary atherosclerosis?

To evaluate the antioxidant hypothesis with regard to atherosclerosis, we compared plasma selenium, serum alpha-tocopherol, serum polyunsaturated fatty acids (PUFA), and the ratios of selenium and alpha-tocopherol to PUFAs in subjects with varying degrees of coronary atherosclerosis. Cases had more than 85% stenosis in at least one coronary vessel and controls had less than 50% stenosis in all three vessels. Plasma selenium was significantly lower in cases than controls (95.1 +/- 21.0 micrograms/l and 108.8 +/- 29.3 micrograms/l, respectively). Though alpha-tocopherol and PUFA levels were similar in both groups, the ratios Se/linoleic acid, Se/total PUFA and Se/total n-6 acids were significantly lower in cases. In particular, these differences were observed in subjects with low serum alpha-tocopherol level (below the median; 1452 micrograms/dl). Moreover, in this subgroup the ratio Se/PUFA was significantly lower in cases than in controls for all PUFAs except eicosapentaenoic and docosahexaenoic acid. Though definitive conclusions cannot be drawn from our data, it is hypothesized that high PUFA levels, when insufficiently protected by antioxidants against peroxidation, may indicate a higher risk of atherosclerosis.

Coronary Artery Disease↗
PubMed1991

Nutritional status and food consumption in 10-11 year old Dutch boys (Dutch Nutrition Surveillance System).

As part of the Dutch Nutrition Surveillance System, cardiovascular risk factors and food consumption (24 h recall) as well as haematological, Fe and vitamin status (A, B6, C) were assessed in 126 Dutch boys aged 10-11 years (response 71%). Body mass index (BMI) and the sum of four skinfolds were strongly associated (r 0.85, P less than 0.01) and 8% of the boys were overweight (BMI greater than 20.1 kg/m2). Elevated serum total cholesterol levels (greater than 4.4 mmol/l) were observed in 38%; total cholesterol and low-density-lipoprotein-cholesterol levels were strongly associated (r 0.88, P less than 0.001). Intake of fat was high (38% of energy) and too much fat was saturated (polyunsaturated: saturated 0.44, guideline: 0.5-1.0), whereas intake of carbohydrate (49% of energy) and dietary fibre was low. About 12% of the boys had insufficient Fe stores (plasma ferritin less than 12.0 micrograms/l) and the mean Fe intake (9.0 mg/d) was below recommended daily allowance (10.0 mg/d). Plasma ferritin was, however, not associated with haematological indices and no frank anaemias were observed. No marginal values were observed for vitamins A, B6 and C status. In conclusion, the main nutritional risks in boys aged 10-11 years are cardiovascular risk factors and Fe nutrition.

Ascorbic Acid↗
PubMed1991

Nutrition and blood pressure among elderly men and women (Dutch Nutrition Surveillance System).

Associations between blood pressure and nutrition-related variables (body mass index, dietary intake, and 24-hr excretion of sodium, potassium, magnesium, and calcium in the urine) were investigated in men (n = 138) and women (n = 117) 65-79 years old not using drugs known to affect blood pressure and not on a diet. Among men, body mass index was positively and creatinine clearance was inversely associated with systolic blood pressure, whereas body mass index and urinary sodium:potassium ratio were positively associated with diastolic blood pressure. Among women, both age and urinary calcium:creatinine ratio were positively associated with systolic as well as diastolic blood pressure. Coffee consumption was positively correlated with blood pressure and urinary calcium:creatinine ratio among the women. From the results it appears that, besides "normal" weight, increased potassium intake and urinary excretion may exert a protective effect among elderly men against hypertension when sodium exposure is relatively high. The positive association between urinary calcium:creatinine ratio and blood pressure among the women may be partly due to coffee consumption.

Aged↗
PubMed1991

Nutrition and serum cholesterol levels among elderly men and women (Dutch Nutrition Surveillance System).

Associations of serum cholesterol with relevant dietary intake variables (assessed with the dietary history method) and body mass index were investigated in elderly men (n = 199) and women (n = 180) 65-79 years old. All subjects were apparently healthy, nondiabetic, and not on a dietary regimen. The associations were studied separately for men and women using linear regression analysis and all possible subsets regression analysis. Among men, body mass index (kg/m2) and intake of monounsaturated fat and of alcohol were positively and consistently associated with serum total cholesterol. Among women, intake of alcohol and of saturated fat were positively associated, and intake of polysaccharides was inversely associated with serum total cholesterol. The intake of monounsaturated fatty acids was highly (r greater than .60) positively correlated with the intake of total fat and saturated fatty acids, and inversely with carbohydrates. HDL-cholesterol was positively associated with alcohol intake (significant for men only), and inversely with body mass index (women). The results indicate that the effect of dietary factors on serum cholesterol levels is probably not age-limited. Elderly people may potentially benefit from weight reduction or control, moderate alcohol consumption, and avoidance of too much dietary fat. These suggestions are in fair accordance with general population-based guidelines for a healthy diet. However, as our study was cross-sectional, causation as well as the public health impact remains to be proven.

Aged↗
PubMed1991

QT interval prolongation predicts cardiovascular mortality in an apparently healthy population.

BACKGROUND: In myocardial infarction patients, heart rate-adjusted QT interval (QTc), an electrocardiographic indicator of sympathetic balance, is prognostic for survival. METHODS AND RESULTS: In a 28-year follow-up, the association between QTc and all-cause, cardiovascular, and ischemic heart disease mortality was studied in a population of 3,091 apparently healthy Dutch civil servants and their spouses, aged 40-65 years, who participated in a medical examination during 1953-1954. Moderate (QTc, 420-440 msec) and extensive (QTc, more than 440 msec) QTc prolongations significantly predict all-cause mortality during the first 15 years among men (adjusted respective relative risks [RRs], 1.5 and 1.7) and among women (RRs, 1.7 and 1.6). In men, cardiovascular (RRs, 1.6 and 1.8) and ischemic heart disease mortality (RRs, 1.8 and 2.1) mainly account for this association. In women, the association cannot be attributed specifically to cardiovascular and ischemic heart disease mortality. RRs for a subpopulation without any sign of heart disease at baseline are similar. The same is observed for QTc prolongation after light exercise, although in this situation most associations are not statistically significant, probably because of smaller numbers in the QTc prolongation categories. CONCLUSIONS: Our results suggest that QTc contributes independently to cardiovascular risk. If autonomic imbalance is an important mechanism, it might be speculated that changes in life-style (e.g., with regard to physical exercise and smoking) may have a preventive impact.

Autonomic Nervous System↗
PubMed1991

Inconsistent associations among anthropometric measurements in elderly Dutch men and women.

In a national survey of 515 apparently healthy Dutch elderly people aged 65 through 79 years, interrelationships among weight, height, weight-for-height indexes (especially the Quetelet index), body fatness (assessed by skinfold measurements), and 24-hour urinary creatinine excretion were investigated in various age groups. Body weight, body height, and 24-hour urinary creatinine excretion (absolute and per kilogram body weight) were lower in older age groups. In men the correlation coefficient between weight and body fatness was .54 for the group aged 65 through 69 years and .33 for the group aged 75 through 79 years. In women the correlation between weight and percentage of body fat varied from .52 to .70 among the age groups. In comparison with results reported for younger adults, a lower correlation between the Quetelet index and body fatness was observed (r = .49 in men, r = .64 in women). The correlation of the Quetelet index with both height and urinary creatinine excretion tended to be higher in the older age groups. We concluded that some of the associations found were inconsistent and that there may be some doubt about the adequacy of the Quetelet index as a measure of body fatness among the elderly. However, no convenient alternative weight-for-height index is presently available. Perhaps circumferences are a better option to choose for elderly people.

Adipose Tissue↗
PubMed1991

Diet and other life-style factors in high and low socio-economic groups (Dutch Nutrition Surveillance System).

Insight into the occurrence of and the association between certain socio-economic variables and life-style characteristics is necessary for preventive nutrition and health policy. The prevalence of and the interdependencies among these variables were examined in 1930 men and 2204 women aged 19 to 85 who participated in the Dutch National Food Consumption Survey 1987-1988. Dietary data were based on a two-day record. The associations among discrete variables were analysed using log-linear models. Analysis of covariance was used to explore the effects of the aggregate socio-economic status (SES) on dietary intake and anthropometry, whereas differences in food intake and SES were assessed by the non-parametric test of Kruskal and Wallis. In comparison to subjects with a high SES in people with a low SES a higher proportion of smokers (48 vs 32 per cent) was observed, a higher prevalence of obesity (39 vs 28 per cent), a higher percentage of heavy coffee drinkers (greater than six cups per day, 23 vs 17 per cent), and more subjects who skipped breakfast (19 vs 11 per cent). In the highest SES class more subjects used nutritional supplements (18 vs 11 per cent), more subjects followed a dietary rule (five vs two per cent), such as a vegetarian diet, and a higher proportion used more than three alcoholic drinks per day (19 vs 15 per cent). A higher SES was associated with a lower fat intake, but the differences (expressed as per cent of energy intake) were rather small and even absent among women when the contribution of alcohol to energy was not taken into account. In general, dietary intake among subjects in higher SES groups tended to be closer to dietary recommendations. The results indicate that a lower SES is accompanied by a higher prevalence of several indicators of an unhealthy life-style.

Adult↗
PubMed1990

Dietary fiber, beta-carotene and breast cancer: results from a case-control study.

To study the association between dietary fiber, beta-carotene and breast cancer, the average daily intake of these dietary components was compared among 133 incident breast cancer cases and 238 population controls. Average daily intake of cereal products, fruit and vegetables was also studied. A statistically significant lower energy-adjusted intake of dietary fiber was observed in cases than in controls (mean +/- SD: 25.4 +/- 6.7 g vs. 27.7 +/- 7.4 g, 95% confidence interval (CI) of the age-adjusted difference = -3.8, -0.8). Intake of beta-carotene was similar for cases and controls. The multivariate adjusted odds ratio (OR) of breast cancer among women in the highest quartile of intake of cereal products, as compared to those in the lowest quartile, was 0.42 (95% CI = 0.19-0.92) and the trend was statistically significant (p = 0.03). The corresponding OR for intake of dietary fiber was 0.55 (95% CI = 0.26-1.17) but the trend was not significant. The OR for the highest quartile of intake of beta-carotene, fruit, vegetables, and all vegetable products combined was less than unity, but there was no significant inverse trend. These results suggest that a high intake of cereal products, especially those rich in fiber, may be inversely related to incidence of breast cancer.

Age Factors↗
PubMed1990

Relation of moderate alcohol consumption and risk of systemic hypertension in women.

The relation between alcohol consumption and the risk of development of hypertension was studied among 58,218 US female registered nurses aged 39 to 59 years who were free of diagnosed systemic hypertension and other major diseases. In 1980, all of these women completed an independently validated dietary questionnaire, which included use of alcoholic beverages. During 4 years of follow-up, 3,275 women reported an initial diagnosis of hypertension; validity of the self-report measure was demonstrated in a subsample. When compared to nondrinkers, women drinking 20 to 34 g of alcohol per day (about 2 or 3 drinks) had a significantly elevated relative risk of 1.4; the 95% confidence interval (CI) was 1.2 to 1.7 after adjustment for age and Quetelet's index. For women consuming greater than 35 g/day, the relative risk was 1.9 (95% CI 1.6 to 2.2). Adjustment for smoking and dietary variables did not alter these results. Independent significant associations were observed for the consumption of beer, wine and liquor. These prospective data suggest that alcohol intake of up to about 20 g/day does not increase the risk of hypertension among women, but beyond this level, the risk increases progressively.

Adult↗
PubMed1990

Duration and reproducibility of initial hemodynamic effects of flosequinan in patients with congestive heart failure.

The duration and reproducibility of hemodynamic effects of flosequian, a direct-acting, balanced-type vasodilator, were studied in 19 heart failure patients (NYHA class 3.0 +/- 0.7) receiving 100 mg orally (day 1), placebo (day 2), and again 100 mg (day 3). Flosequinan immediately reduced systemic and pulmonary resistance (23% and 35%, respectively, at 60-90 minutes postdrug) and decreased pulmonary wedge, right atrial, mean pulmonary artery, and mean arterial pressure by 38%, 50%, 25%, and 7%, respectively. Concomitantly, cardiac output, and stroke volume and work increased by 26%, 20%, and 22%, respectively. Most hemodynamic effects persisted for 48 hours. In contrast, changes in pulmonary wedge and arterial pressures, stroke volume, and stroke work only lasted for 2-12 hours. Maximum absolute changes on day 3 were generally comparable with first-dose effects with, again, long-lasting effects on systemic resistance and cardiac output. However, changes in pulmonary artery, wedge, and resistance were significantly shorter than after first dose administration. These data indicate sustained and reproducible arterial dilating effects of flosequinan, but less pronounced and shorter lasting pulmonary arterial and venodilator properties.

Aged↗