David Hewitt

Magnesium and certain other elements and cardiovascular disease

Cardiovascular disease (CVD) continues to be the major cause of mortality in developed countries. For the past two-and-a-half decades the inverse relationship between water hardness and CVD mortality has stimulated interest among epidemiologists, clinicians and experimental researchers. Much progress has been made in elucidating which element in the water may account for this situation. After reviewing those elements found to have a role in cardiovascular function the authors present the epidemiological evidence and its consistency with recent findings: aside from various trace elements emphasis is placed on magnesium which is recognized as having a vital role.

Heritability of "sinking" pre-beta lipoprotein level: a twin study.

In a twin series at the Toronto Twin Register, University of Toronto, the “sinking” pre‐beta lipoprotein fraction (sp β), quantitatively determined, was found to have a heritability index of 0.98. If confirmed, this warrants use of spβ concentration as a genetic marker. Its importance may lie in its association with angina of effort and myocardial infarction.

The inheritance of sinking-pre-beta lipo-protein and its relation to the Lp(a) antigen*

We have investigated the genetics of plasma sinking‐pre‐beta lipoprotein (spβ) as determined by the method of Breckenridge and Maguire, using several approaches: (i) a population study, (ii) a twin study and (iii) the use of family data. In addition, by the use of split samples, the spβ level as determined by us was correlated with Lp(a) typing carried out in Oslo by Dr. Kåre Berg. Although the spβ level is a continuous character, the results clearly showed it to be to a considerable extent under the control of the major autosomal gene pair constituted by the alleles Lpa and Lp, which mainly control the production of the Lp(a) antigen, Lpa being dominant. In our data the boundary between the LpLp and Lpa Lp genotypes appeared to fall between the spβ 2 and 3 mg% levels, while that between Lpa Lp and Lpa Lpa was in the 15 mg% region. These boundaries, which were inferred from both typing and population statistics, received good confirmation from the family data. It appears that some 88% of the variation in spp level is directly ascribed to segregation of Lpa and Lp. On the basis of the twin study and other data, we conclude that the residual observed variation in spβ is almost entirely ascribed to analytical error of determination and polygenic effects, the influence of environment being negligible. The heritability is close to 100%.

Mortality from cardiovascular-renal diseases in Ontario and elsewhere 1—Descriptive. 2—Analytic

Abstract Attention was drawn in Part 1 to some features of the mortality from cardio-vascular-renal diseases in individual counties of Ontario and in other Provinces. In particular, the mortality attributed to hypertensive disease and to nephritis shows highly patterned geographical variation for which an explanatory hypothesis is offered. Part 2 deals with some of the problems occasioned by defects in death certificate data and proposes three techniques for dealing with them:- 1. (i) use of a criterion, based on the intercorrelations among cause-specific mortalities, which tests whether reported regional variation could be entirely spurious; 2. (ii) construction of an index of comparability between areas based on known characteristics of the physicians practicing in each area; 3. (iii) application of a significance test in which each sex is used as a control group for the other. This study was assisted by funds provided by the Research Position in Epidemiology grant (No. 605-7-434) of the National Health Grants Programme.

The occurrence and treatment of gallbladder disease in Ontario

GALLBLADDER disease is currently among the top ten reasons for admission to hospital in Ontario where, at any one time, upwards of a thousand active treatment beds are occupied by patients with a primary diagnosis of cholecystitis or cholelithiasis. While the frequency of fatal cases is declining, the total incidence of treated cases appears to be on the increase in Ontario, and increases have also been reported from other parts of Canada [l-3]. In the present report an attempt is made to characterize the amount and distribution of gallbladder disease in this Province, using data from a variety of official publications [4-g], supplemented from unpublished tables prepared by the Ontario Hospital Services Commission [lo] and from a first-hand scrutiny of some 43,000 discharge summaries relating to surgical patients, of whom 7573 had operations on the gallbladder.

Choice of Objectives in Atherosclerosis Prevention

What is the true value of any recommendation that an expert group, such as yourselves, can make?