Dietary antioxidants and risk of myocardial infarction in the elderly: the Rotterdam Study

BACKGROUND: Epidemiologic studies have shown dietary antioxidants to be inversely correlated with ischemic heart disease. OBJECTIVE: We investigated whether dietary beta-carotene, vitamin C, and vitamin E were related to the risk of myocardial infarction (MI) in an elderly population. DESIGN: The study sample consisted of 4802 participants of the Rotterdam Study aged 55-95 y who were free of MI at baseline and for whom dietary data assessed by a semiquantitative food frequency questionnaire were available. During a 4-y follow-up period, 124 subjects had an MI. The association between energy-adjusted beta-carotene, vitamin C, and vitamin E intakes and risk of MI was examined by multivariate logistic regression. RESULTS: Risk of MI for the highest compared with the lowest tertile of beta-carotene intake was 0.55 (95% CI: 0.34, 0.83; P for trend = 0.013), adjusted for age, sex, body mass index, pack-years, income, education, alcohol intake, energy-adjusted intakes of vitamin C and E, and use of antioxidative vitamin supplements. When beta-carotene intakes from supplements were considered, the inverse relation with risk of MI was slightly more pronounced. Stratifica

Dietary assessment in the elderly: Application of a two-step semiquantitative food frequency questionnaire for epidemiological studies

Objective: Description and application of an adapted semiquantitative food frequency questionnaire (SFFQ) for dietary assessment in the elderly population of the Rotterdam Study. Design: Dietary assessment consisting of a two-step approach was performed in 5434 participants (2225 men, 3029 women) of the Rotterdam Study from 1990 to 1993, a population-based prospective cohort of 7983 subjects aged 55-95 years (participation rate 78%). Statistical analysis: Nutrient intake was calculated for men and women in four age groups (55-64 years, 65-74 years, 75-84 years, 85-95 years) and linear trend analysis for differences in mean nutrient intake across age groups (55-64 gears 65-74 years, 75-95 years) by regression analysis was conducted. The influence of baseline characteristics on energy and nutrient intakes adjusted by age and sex was investigated by one-way-analysis of variance. Results: The adapted SFFQ made it possible to measure nutrient intake in the elderly within a limited time frame (2 x 20 min) across a wide age range (55-95 years). For nutrient intake we observed a general decline in mean intake of energy and most nutrients with age in men. In women the relation with age was not consistent: for most nutrients mean intake showed a decrease with age (e.g. water, magnesium, potassium), for some an incre

The Implications of Sequential Investment in the Property Rights Theory of the Firm

In the property rights theory of the firm, control over assets (ownership) affords bargaining power in the case of re-negotiation, providing incentives for parties to make relationship specific investments. The models predict that property rights will be allocated so as to maximise surplus generated from investment. However, these models assume that investments are made simultaneously. In this thesis I extend the standard property-rights framework to allow for sequential investment; the model allows for two investment periods. If a party invests first (ex-ante), they sink their investment before any contracting is possible. The parties that invest second (ex-post) do so after some aspects of the project are tangible, so that they can contract on (at least some) of their investment costs. As well as being empirically relevant, sequencing has several important theoretical implications. First, if a party gets to invest second, then – ceteris paribus – it has a greater incentive to invest. Second, the investment of parties that invest first are affected by a more than one influence. Anticipating higher ex-post investment, they can have a greater incentive to increase their investments. However, higher ex-post investment leads to greater costs being borne by the ex-ante investors (via the cost sharing contracts); this reduces ex-ante incentives to invest. Overall either effect can dominate so that ex-ante investment can either increase or decrease as a result of sequential investment. Third, as noted, sequencing of investment provides the possibility to (partially) contract on ex-post investment and costs. This is an additional method of providing incentives to invest, beyond the allocation of property rights themselves. Consequently, ex-post investors can be protected (and be provided incentives to invest) via these contracts, whereas ex-ante investors –who can not contract on their investments at all – are more likely to require the protection of property rights (through the allocation of asset ownership). The addition of sequential investment alters some of the predictions of the standard models. For example, previously the literature found that if all assets are complements at the margin all agents should have access to all assets (Bel (2005)). However, when investment sequencing is possible, making a control structure more inclusive (increasing the number of agents who have access to assets) can reduce the incentives of the ex-ante investors, decreasing overall surplus; this is because increasing the property rights of ex-post investors increases the marginal costs borne by ex-ante investors, effectively reducing their claim on surplus, diminishing their incentives to invest. This result contradicts Bel (2005), and shows that even when all assets are complimentary at the margin allocating access rights can be detrimental to incentives. Furthermore, if assets are substitutes at the margin then transfer of assets from ex-ante investors to ex-post investors can increase ex-ante investment and surplus. This counter intuitive result can occur in the case when decreasing ex-post investment is necessary to provide an incentive to ex-ante investors to increase their investments.Discipline of Economic

Dietary iron and risk of myocardial infarction in the Rotterdam Study

Free iron has been implicated in lipid peroxidation and ischemic myocardial damage, and it has been suggested that iron is an independent risk factor for myocardial infarction. The authors investigated whether dietary iron is associated with an increased risk of fatal and nonfatal myocardial infarction in the Rotterdam Study, a community-based prospective cohort study of 7,983 elderly subjects in Rotterdam, the Netherlands. The study sample consisted of 4,802 participants who at baseline had no known history of myocardial infarction and for whom dietary data were available. From 1990 to 1996, 124 subjects had a myocardial infarction. No association was observed between total iron intake and risk of myocardial infarction after adjustment for age and sex (relative risk for the highest vs. the lowest tertile of intake=0.89, 95% confidence interval (CI) 0.55-1.45, p for trend=0.640). Heme iron intake was positively associated with risk of myocardial infarction (relative risk for the highest vs. the lowest tertile of intake=1.83, 95% Cal 1.16-2.91, p for trend=0.008) after adjustment for age and sex, and this association persisted after multivariate adjustment (relative risk=1.86, 95% Cal 1.14-3.09, p for trend=0.010). A distinction between fatal and nonfatal cases of myocardial infarction indicated that the association of heme iron with myocardial infarction was more pronounced in fatal cases. The results suggest that a high dietary heme iron intake is related to an increased risk of myocardial infarction and that it may specifically affect the rate of fatality from myocardial infarction

Dietary assessment in the elderly: Validation of a semiquantitative food frequency questionnaire

Objective: The study was conducted to assess the relative validity of a 170-item semiquantitative food frequency questionnaire (SFFQ) adapted for use in the elderly. Design and subjects: The study was carried out in a sample of 80 men and women aged 55-75 y participating in a community based prospective cohort study in Rotterdam, The Netherlands. The two-step dietary assessment comprised a simple self-administered questionnaire (20 min) followed by a structured interview with trained dietitians (20 min) based on the completed questionnaire. Multiple food records (FR) collected over a one year period served as reference method. 24 h urine urea was used as indirect marker for protein intake. Results: Compared with FR, the SFFQ generally overestimated nutrient intake as reflected by difference in means and the ratio of SFFQ to FR. Energy adjustment reduced the observed overestimation. Pearson's correlation coefficients varied from close to 0.5 to about 0.9 for crude data, and after adjustment for age, sex, total energy intake, and for within-person variability in daily intake for 0.4-0.8. Cross-classification into quintiles resulted in correct classification into the same or adjacent quintile of 75.8% for crude and 76.8% for energy adjusted data. Validation of protein intake estimated by SFFQ with protein excretion from 24 h urine urea indicated overestimation of protein intake by SFFQ. Spearman correlation coefficient between protein intake estimated from urea excretion and SFFQ was 0.67. Conclusions: Adaptation of a SEFQ for use in the elderly resulted in a valid and time-efficient dietary assessment instrument. Its ability to adequately rank study subjects according to their dietary intake support its application in epidemiological studies in the elderly

Dietary electrolyte intake and blood pressure in older subjects. The Rotterdam Study

Objective. To examine the relation between dietary electrolyte intake and blood pressure in older people. Methods. The study included 3239 participants of the Rotterdam Study (41% of the total cohort) who were aged over 55 years and had not been prescribed antihypertensive drugs. Their dietary intake was assessed by a semiquantitative food frequency questionnaire. The association of energy-adjusted intakes of potassium, magnesium and calcium with blood pressure was studied in a linear regression model with adjustment for age, sex, body mass index and alcohol intake. Results. An increase in potassium intake of 1 g/day was associated with a 0.9 mmHg lower systolic and a 0.8 mmHg lower diastolic blood pressure. An increase in magnesium intake of 100 mg was associated with a 1.2 mmHg lower systolic and a 1.1 mmHg lower diastolic blood pressure. Calcium intake was not independently related to blood pressure, except for a subgroup of 1360 hypertensive subjects in which a significant inverse association with diastolic blood pressure was observed. Conclusions. Our findings support the view that an increase in the intake of foods rich in potassium and magnesium could lower blood pressure at older age