Climate, water hardness and coronary heart disease

Temporal changes in the spatial pattern of disease rates incorporating known risk factors

Examining the geographical pattern of temporal changes in infant mortality rates illustrates the methodological problems of documenting and understanding temporal changes in any spatial pattern of disease. Early research on geographical differences in infant mortality rates showed strong ecological correlations with socio-economic factors such as poverty rates. More recent research established relationships between individual-level socio-economic values and probabilities of death. With geographic information available at the level of individuals, it is possible to estimate the probabilities of death on a person-by-person basis from knowledge of the relationships between individual factors and socio-economic measures. These estimated probabilities provide an expected geographic pattern of deaths. The difference between the observed spatial pattern and the expected pattern is the remaining spatial variation adjusted for this knowledge. For the study area, individual factors and some socio-economic measures were available for each year of the study period. Using data from the Iowa Birth Defects Registry and the Iowa Department of Public Health (USA), I tested the stability and continuity of these cross-sectional relationships and investigated whether any temporal lags in these variables relate to the unexplained spatial variations in infant mortality rates that remain. I accounted for the 'Change of Support Problem' [Gotway C. A. & Young L. J. (2002). Combining incompatible spatial data. Journal of the American Statistical Association, 97458, 632-648] inherent in frame-based geographical analysis. The analysis involved a generalized linear model (GLM) to estimate individual risks and a Monte Carlo simulation model to generate the non-linear probability density functions for disease rates whose densities are theoretically intractable. Results show the temporal changes in the observed spatial pattern and the expected spatial pattern differ by geographic location. In conclusion such differences are the result of a combination of unexplained place-based risk and unmeasured individual risks.

Relation between all cause standardised mortality ratios and two indices of deprivation at regional and district level in England

The use of mortality data in the form of standardised mortality ratios (SMRs) to measure the need for health care resources in the Resource Allocation Working Party (RAWP) formula in England has been criticised for underestimating the wider effects of adverse socioeconomic conditions on need, particularly in inner city areas. To assess this criticism, we explored the relationships at NHS Regional and District levels in England between two indicators of illness from the 1981 Census, two contrasting indices of deprivation based on the 1981 Census (the Jarman 8 Underprivileged Area (UPA) score and Townsend's Index of Material Deprivation) and their constituent variables, and all cause SMRs for 1982-3. All cause SMRs were highly correlated at Regional and District level with permanent and temporary sickness rates. At Regional level, three of the Thames Regions showed relatively high deprivation scores in relation to their SMRs, in comparison to the remaining Regions where the relative level of deprivation closely matched the Region's mortality ranking. District level analyses of the relations between SMRs and the deprivation indices and their constituent variables showed that the Thames/non-Thames dichotomy was accounted for by the 14 Districts in inner London. These findings suggest that although there may be a prima facie case for including an allowance for deprivation in RAWP, it is still not clear how the deprivation variables available in the Census relate empirically to the need for additional health service resources. The analysis raises questions about the appropriate definition of need in this context and whether the Census is a suitable source for the construction of a deprivation weighting for use in national RAWP.

Water and arteriosclerosis

Consumption of hard water is presumed to protect against the development of arteriosclerotic diseases. Substantial epidemiologic correlations support the "hard water effect" as sufficiently valid to warrant alteration of public water supplies as a public health measure. A recently proposed theory that arteriosclerosis is an indolent, chronic, infectious disease caused by cyanobacteria suggests that an alternate explanation may be possible. The relationship between hard water and arteriosclerosis is reviewed, contradictions and exceptions noted, and an alternate theory of microbial infection is offered.

The seasonal variation in mortality from cerebrovascular disease

The frequency distribution of deaths from cerebrovascular disease in England and Wales in 1975 by month of occurrence is described. The distribution is compared with that for related diseases, in particular ischaemic heart disease, hypertensive disease, pneumonia and bronchitis. The principal feature in all these diseases is high mortality in winter and spring and low mortality in late summer, but the range of variation is wider for pneumonia and bronchitis. The seasonal distribution of cerebrovascular disease death is similar in both sexes, all ages at death and for deaths at home and deaths in a hospital or institution. For both sexes the proportion of cerebrovascular disease deaths occurring at home increases significantly with age at death. Four hypotheses are examined to explain this characteristic seasonal mortality pattern, which is related inversely to ambient temperature, and similar to the seasonal pattern of the incidence and prevalence of cerebrovascular disease.

The relation of mortality in England and Wales 1969-1973 to measurements of air pollution

The relation between mortality of people aged 45 to 74 and atmospheric smoke and sulphur dioxide in the county and London boroughs of England and Wales was investigated using data for the years 1969 to 1973. Weighted multiple regression analyses, which took into account a number of socioeconomic and climatic variables, showed no consistent relation of smoke or sulphur dioxide with mortality from all causes or with mortality from specified causes postulated a priori to be related to pollution. In particular there was no significant association between smoke and mortality rates for respiratory illness. Comparison with results from similar analyses of data for the two previous decades suggested that a decline in the strength of associations had occurred in parallel with declining levels of the pollutants.

British Regional Heart Study: geographic variations in cardiovascular mortality, and the role of water quality

In a study of regional variations in cardiovascular mortality in Great Britain during 1969-73 based on 253 towns the possible contributions of drinking water quality, climate, air pollution, blood groups, and socioeconomic factors were evaluated. A twofold range in mortality from stroke and ischaemic heart disease was apparent, the highest mortality being in the west of Scotland and the lowest in south-east England. A multifactorial approach identified five principal factors that substantially explained this geographic variation in cardiovascular mortality-namely, water hardness, rainfall, temperature, and two social factors (percentage of manual workers and car ownership). After adjustment for other factors cardiovascular mortality in areas with very soft water, around 0.25 mmol/l (calcium carbonate equivalent 25 mg/l), was estimated to be 10-15% higher than that in areas with medium-hard water, around 1.7 mmol/l (170 mg/l), while any further increase in hardness beyond 1.7 mmol/l did not additionally lower cardiovascular mortality.Thus a negative relation existed between water hardness and cardiovascular mortality, although climate and socioeconomic conditions also appeared to be important influences. Cross-sectional and prospective surveys of 7500 middle-aged men from 24 towns are in progress and will permit further exploration of these geographic differences, especially with regard to personal risk factors such as blood pressure, blood lipid concentrations, and cigarette smoking.

The water factor and mortality from ischemic heart disease: a review and possible explanations for inconsistent findings with additional data from Manitoba

The question of the relationship between water hardness and mortality from cardiovascular diseases is far from being settled. Marked discrepancies in the results of various studies in this area exist and there is a great need for closer examination of the reliability of measuring water hardness and other water characteristics. There is also a need for standardizing these measurements and for accounting for certain important questions in designing studies of this nature. This article reviews the results of various studies on the "water factor," points out their discrepancies, presents additional evidence from the Province of Manitoba against the "water factor;" and explains possible sources for discrepancies in the findings of various studies. Based on the evidence so far available, it is too early to universally accept the "water story" and to make recommendations for discouraging the softening of hard water as a measure for preventing cardiovascular disease mortality.