Magnesium in drinking water supplies and mortality from acute myocardial infarction in north west England

The role of magnesium in cardiac arrest

Cardiac arrest is a leading cause of death globally. Only 25.8% of in-hospital and 33.5% of out-of-hospital individuals who achieve spontaneous circulation following cardiac arrest survive to leave the hospital. Respiratory failure and acute coronary syndrome are the two most common etiologies of cardiac arrest. Effort has been made to improve the outcomes of individuals resuscitated from cardiac arrest. Magnesium is an ion that is critical to the function of all cells and organs. It is often overlooked in everyday clinical practice. At present, there have only been a small number of reviews discussing the role of magnesium in cardiac arrest. In this review, for the first time, we provide a comprehensive overview of magnesium research in cardiac arrest focusing on the effects of magnesium on the occurrence and prognosis of cardiac arrest, as well as in the two main diseases causing cardiac arrest, respiratory failure and acute coronary syndrome. The current findings support the view that magnesium disorder is associated with increased risk of cardiac arrest as well as respiratory failure and acute coronary syndrome.

Impact of drinking water hardness on carotid atherosclerosis and arterial stiffness: Insights from the "Corinthia" study

BACKGROUND

Several investigations have highlighted the role of water quality in cardiovascular health. In the present study, we have investigated the effects of drinking water hardness on atherosclerotic burden in carotid arteries and arterial stiffness.

METHODS

"Corinthia" study was conducted in the homonym region in Greece from 2015 to 2017. Carotid atherosclerosis was assessed by intima-media thickness (IMT). Pulse wave velocity (PWV) was used to evaluate arterial stiffness. Tap-water samples were collected from the study area and analyzed for a variety of elements, as well as pH and total hardness.

RESULTS

Individuals living in lower drinking water hardness areas (Area 1) versus individuals living in higher water hardness areas (Area 2) had lower max IMT (p = 0.004) and were less susceptible to carotid plaque formation (p = 0.004). Interestingly, individuals over 65 years from Area 1 had lower mean IMT, max IMT, and less plaque formation (p < 0.001 for all). The mean value of PWV in the overall study population was below the 10 m/s cutoff, which defines arterial stiffness (9.15 ± 2.79 m/s). Nevertheless, a marginally higher rate of vascular stiffening was noted in Area 2 vs. Area 1 (16.2% and 12.8%, respectively, p = 0.048).

CONCLUSIONS

According to this cross-sectional study's findings, a positive association between extra hard water and carotid atherosclerotic burden was found. However, the association with arterial stiffness is unclear and should be investigated further.

Drinking water magnesium and cardiovascular mortality: A cohort study in Denmark, 2005-2016

INTRODUCTION

Cardiovascular diseases are globally a major cause of death. Magnesium deficiency is associated with several diseases including cardiovascular diseases.

OBJECTIVE

To examine if a low concentration of magnesium in drinking water is associated with increased cardiovascular mortality and mortality due to acute myocardial infarction and stroke.

METHODS

A nationwide population-based cohort study using national health registries was used. A total of 4,274,132 individuals aged 30 years or more were included. Magnesium concentration in drinking water was estimated by linkage of residential addresses in the period 2005-2016 with the national drinking water quality monitoring database. The association between magnesium concentration in drinking water and cardiovascular mortality and mortality due to acute myocardial infarction and stroke was examined using a Poisson regression of number of deaths and logarithmic transformation of follow-up time as offset. The incidence rate ratio (IRR) was adjusted for differences in age, sex, calendar year, cohabitation, country of origin, and socioeconomic status.

RESULTS

Median magnesium concentration in drinking water at inclusion was 12.4 mg/L (range: 1.37-54.2 mg/L). The adjusted IRR for cardiovascular mortality was 0.96 (95% CI: 0.94; 0.97) for the lowest magnesium quintile (<6.5 mg/L) as compared to the highest magnesium quintile (>21.9 mg/L). The adjusted IRR for mortality due to acute myocardial infarction and stroke was 1.22 (1.17; 1.27) and 0.96 (0.93; 0.99), respectively, for the lowest magnesium quintile as compared to the highest quintile A decreasing mortality due to acute myocardial infarction was seen with an increasing magnesium concentration in a dose-response manner.

CONCLUSION

Low concentrations of magnesium in drinking water were associated with an increased mortality due to acute myocardial infarction. Low concentrations of magnesium in drinking water were associated with decreased cardiovascular mortality, and mortality due to stroke.

Association between magnesium in drinking water and atrial fibrillation incidence: a nationwide population-based cohort study, 2002-2015

BACKGROUND

Atrial fibrillation (AF) is a common heart rhythm disorder and a risk factor of adverse cardiovascular diseases. Established causes do not fully explain the risk of AF and unexplained risk factors might be related to the environment, e.g. magnesium in drinking water. Low magnesium levels in drinking water might be associated with higher risk of cardiovascular diseases including AF. With detailed individual data from nationwide registries and long-term magnesium exposure time series, we had a unique opportunity to investigate the association between magnesium in drinking water and AF.

OBJECTIVE

We evaluated the association between magnesium concentration in drinking water and AF risk.

METHODS

A nationwide register-based cohort study (2002-2015) was used including individuals aged ≥30 years. Addresses were linked with water supply areas (n = 2418) to obtain time-varying drinking water magnesium exposure at each address. Five exposure groups were defined based on a 5-year rolling time-weighted average magnesium concentration. AF incidence rate ratios (IRRs) between exposure groups were calculated using a Poisson regression of incidence rates, adjusted for sex, age, and socioeconomic position. Robustness of results was investigated with different exposure definitions.

RESULTS

The study included 4,264,809 individuals (44,731,694 person-years) whereof 222,998 experienced an incident AF. Magnesium exposure ranged from 0.5 to 62.0 mg/L (mean = 13.9 mg/L). Estimated IRR (95% CI) compared to the referent exposure group (< 5 mg/L) was 0.98 (0.97-1.00) for the second lowest exposure group (5-10 mg/L), and 1.07 (1.05-1.08) for the two highest exposure groups (15-62 mg/L). Strongest positive associations were observed among those aged ≥80 years and with lowest education group. An inverse association was found among individuals with highest education group.

CONCLUSION

There might be a small beneficial effect on AF of an increase in magnesium level in drinking water up to 10 mg/L, though an overall positive association was observed. The unexpected positive association and different associations observed for subgroups suggest a potential influence of unaccounted factors, particularly in vulnerable populations. Future research on magnesium in drinking water and cardiovascular diseases needs to focus on contextual risk factors, especially those potentially correlating with magnesium in drinking water.

Vibrio cholerae biofilm scaffolding protein RbmA shows an intrinsic, phosphate-dependent autoproteolysis activity

Vibrio cholerae is the causative agent of the diarrheal disease cholera, for which biofilm communities are considered to be environmental reservoirs. In endemic regions, and after algal blooms, which may result from phosphate enrichment following agricultural runoff, the bacterium is released from biofilms resulting in seasonal disease outbreaks. However, the molecular mechanism by which V. cholerae senses its environment and switches lifestyles from the biofilm‐bound state to the planktonic state is largely unknown. Here, we report that the major biofilm scaffolding protein RbmA undergoes autocatalytic proteolysis via a phosphate‐dependent induced proximity activation mechanism. Furthermore, we show that RbmA mutants that are defective in autoproteolysis cause V. cholerae biofilms to grow larger and mechanically stronger, correlating well with the observation that RbmA stability directly affects microbial community homeostasis and rheological properties. In conclusion, our biophysical study characterizes a novel phosphate‐dependent breakdown pathway of RbmA, while microbiological data suggest a new, sensory role of this biofilm scaffolding element.

Association between exposure to desalinated sea water and ischemic heart disease, diabetes mellitus and colorectal cancer; A population-based study in Israel

BACKGROUND

Drinking water (DW) is an important dietary source of magnesium. Recently, Israel has increased its use of desalinated seawater (DSW) as DW country-wide. Its negligible magnesium content, however, raises concern that consumption of DSW may be associated with hypomagnesemia and increase the risk of ischemic heart disease (IHD), diabetes mellitus (DM), and colorectal cancer (CRC).

OBJECTIVES

We tested whether there was a change in incidence of negative health outcomes (IHD, DM, and CRC) following the introduction of DSW supply in a population-based ecologic study in Israel.

METHODS

A historical prospective analysis was applied to members aged 25-76 during 2004-2013 of Clalit Health Services (Clalit), the largest healthcare provider in Israel, using its electronic medical record database. Multivariable analyses were adjusted for age, sex, socioeconomic status, smoking status, and body mass index.

RESULTS

An increased odds ratio was found for IHD (0.96, 95% CI 0.93-0.99 at baseline and 1.06, 95% CI 1.02-1.11 at the end of the follow-up period), but no time trend was observed.

CONCLUSIONS

We found that the risk for IHD increased during the study period. The risks for DM and CRC were unchanged. Long term studies are needed for assessing the risk for CRC due to the long latency. The higher risk for IHD has practical public health implications and raise the need to add magnesium to DSW.

Cardiovascular diseases and hard drinking waters: implications from a systematic review with meta-analysis of case-control studies

This systematic review with meta-analysis, performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, aims at evaluating the potential correlation between magnesium and calcium concentration in drinking waters and the risk of cardiovascular diseases (CVD), which impose a considerable burden in high-income countries. Included studies were of the case-control studies type. From an initial list of 643 potentially eligible articles, seven studies were finally retained in the quantitative analysis. Since each one of them assessed different ion concentrations, subjects exposed to the highest concentration versus those exposed to the lowest concentration were compared. By including an overall figure of 44,000 subjects, the result suggests a protective effect of the ions on CVD prevention, with an effect-size (ES) of 0.82 (95% confidence interval CI = [0.70-0.95], p-value = 0.008) for calcium, and ES = 0.75 (95% CI = [0.66-0.86], p-value = 0.000) for magnesium. Hard water consumption seems to be protective against CVD. However, the high heterogeneity (I² = 75.24, p-value = 0.001 for calcium; I² = 72.96, p-value = 0.0024 for magnesium) and the existence of publication bias limits the robustness and generalizability of these findings. Further high-quality studies are needed to reproduce and confirm these results.

Review of epidemiological studies on drinking water hardness and cardiovascular diseases

BACKGROUND

Major risk factors do not entirely explain the worldwide variability of morbidity and mortality due to cardiovascular disease. Environmental exposures, including drinking water minerals may affect cardiovascular disease risks.

METHOD

We conducted a qualitative review of the epidemiological studies of cardiovascular disease and drinking water hardness and calcium and magnesium levels.

RESULTS

Many but not all ecological studies found an inverse (i.e., protective) association between cardiovascular disease mortality and water hardness, calcium, or magnesium levels; but results are not consistent. Some case-control studies and one cohort study found either a reduced cardiovascular disease mortality risk with increased drinking water magnesium levels or an increased risk with low magnesium levels. However, the analytical studies provide little evidence that cardiovascular risks are associated with drinking water hardness or calcium levels.

CONCLUSION

Information from epidemiological and other studies supports the hypothesis that a low intake of magnesium may increase the risk of dying from, and possibly developing, cardiovascular disease or stroke. Thus, not removing magnesium from drinking water, or in certain situations increasing the magnesium intake from water, may be beneficial, especially for populations with an insufficient dietary intake of the mineral.

Natural fluoride in drinking water and myocardial infarction: A cohort study in Sweden

Large geographical variation in the coronary heart disease (CHD) incidence is seen worldwide and only a part of this difference is attributed to the classic risk factors. Several environmental factors, such as trace elements in the drinking water have been implicated in the pathogenesis of CHD. The objective was to assess the association between drinking water fluoride exposure and myocardial infarction in Sweden using nationwide registers. This large cohort consisted of 455,619 individuals, born in Sweden between January 1, 1900 and December 31, 1919, alive and living in their municipality of birth at the time of start of follow-up. Estimated individual drinking water fluoride exposure was stratified into four categories: very low (<0.3mg/l), low (0.3-<0.7mg/l), medium (0.7-<1.5mg/l) and high (≥1.5mg/l). In Cox regression analyses, compared to the very low fluoride group, the adjusted Hazard Ratio for the low fluoride group was 0.99 (95% confidence interval, 0.98-1.00), for the medium fluoride group 1.01 (95% confidence interval, 0.99-1.03) and 0.98 (95% confidence interval, 0.96-1.01) for the highest fluoride group. Adding water hardness to the model did not change the results. We conclude that the investigated levels of natural drinking water fluoride content does not appear to be associated with myocardial infarction, nor related to the geographic myocardial infarction risk variation in Sweden. Potential misclassification of exposure and unmeasured confounding may have influenced the results.

Desalinated seawater supply and all-cause mortality in hospitalized acute myocardial infarction patients from the Acute Coronary Syndrome Israeli Survey 2002-2013

BACKGROUND

Consuming desalinated seawater (DSW) as drinking water (DW) may reduce magnesium in water intake causing hypomagnesemia and adverse cardiovascular effects.

METHODS

We evaluated 30-day and 1-year all-cause mortality of acute myocardial infarction (AMI) patients enrolled in the biannual Acute Coronary Syndrome Israeli Survey (ACSIS) during 2002-2013. Patients (n=4678) were divided into 2 groups: those living in regions supplied by DSW (n=1600, 34.2%) and non-DSW (n=3078, 65.8%). Data were compared between an early period [2002-2006 surveys (n=2531) - before desalination] and a late period [2008-2013 surveys (n=2147) - during desalination].

RESULTS

Thirty-day all-cause-mortality was significantly higher in the late period in patients from the DSW regions compared with those from the non-DSW regions (HR=2.35 CI 95% 1.33-4.15, P<0.001) while in the early period there was no significant difference (HR=1.37 CI 95% 0.9-2, P=0.14). Likewise, there was a significantly higher 1-year all-cause mortality in the late period in patients from DSW regions compared with those from the non-DSW regions (HR=1.87 CI 95% 1.32-2.63, P<0.0001), while in the early period there was no significant difference (HR=1.17 CI 95% 0.9-1.5, P=0.22). Admission serum magnesium level (M±SD) in the DSW regions (n=130) was 1.94±0.24mg/dL compared with 2.08±0.27mg/dL in 81 patients in the non-DSW (P<0.0001).

CONCLUSIONS

Higher 30-day and 1-year all-cause mortality in AMI patients, found in the DSW regions may be attributed to reduced magnesium intake secondary to DSW consumption.

Magnesium Levels in Drinking Water and Coronary Heart Disease Mortality Risk: A Meta-Analysis

Epidemiological studies have demonstrated inconsistent associations between drinking water magnesium levels and risk of mortality from coronary heart disease (CHD); thus, a meta-analysis was performed to assess the association between them. Relevant studies were searched by the databases of Cochrane, EMBASE, PubMed and Web of Knowledge. Pooled relative risks (RR) with their 95% CI were calculated to assess this association using a random-effects model. Finally, nine articles with 10 studies involving 77,821 CHD cases were used in this study. Our results revealed an inverse association between drinking water magnesium level and CHD mortality (RR = 0.89, 95% CI = 0.79-0.99, I² = 70.6). Nine of the 10 studies came from Europe, and the association was significant between drinking water magnesium level and the risk of CHD mortality (RR = 0.83, 95% CI = 0.69-0.98). In conclusion, drinking water magnesium level was significantly inversely associated with CHD mortality.

On the Analysis of Diseases and Their Related Geographical Data

Electronic medical records (EMRs) store data related to patients information enrolled during their stay in health structures. Data stored into EMRs span from data crawled from biological laboratories to textual description of diseases and diagnostic device results (e.g., biomedical images). Each EMR is related to a diagnosis related group (DRG) record. A DRG record is a record associated with a citizen that has been cured in a hospital. It contains a code, called major diagnostic category (MDC), which summarizes the treated disease and allows to reimburse costs related to patient treatments during his staying in health structures. DRGs are used for administrative process (e.g., costs and reimbursement management) as well as disease monitoring. Associating diagnostic codes with external information (such as environmental and geographical data) and with information filtered from EMRs (e.g., biological results or analytes values) can be useful to monitor citizens wellness status. We propose a methodology to analyze such data based on a multistep process. First, we cross reference data by using a semantics-based clustering procedure, extract information from EMRs, and then, cluster them by looking for similar patterns of diseases. Then, biological records in each disease cluster are analyzed to evaluate intracluster similarity by selecting analytes typologies and values. Finally, biological data is related to diagnosis codes and geometrically projected in areas of interest in order to map calculated outlier patients. We applied the methodology on two case studies: 1) diagnosis codes and biochemical analytes of 20 000 biological analyses about hospitalized patients during one observation year and 2) the correlation between cardiovascular diseases and water quality in a southern Italian region. Preliminary findings show the effectiveness of our method.

Chemical composition of groundwater and relative mortality for cardiovascular diseases in the Slovak Republic

The study deals with the analysis of relationship between chemical composition of the groundwater/drinking water and the data on relative mortality for cardiovascular diseases (ReI) in the Slovak Republic. Primary data consist of the Slovak national database of groundwater analyses (20,339 chemical analyses, 34 chemical elements/compounds) and data on ReI collected for the 10-year period (1994-2003). The chemical and health data were unified in the same form and expressed as the mean values for each of 2883 municipalities within the Slovak Republic for further analysis. Artificial neural network was used as mathematic method for model data analysis. The most significant chemical elements having influence on ReI were identified together with their limit values (maximal acceptable, minimal necessary and optimal). Based on the results of calculations, made through the neural networks, the following ten chemical elements/parameters in the groundwater were defined as the most significant for ReI: Ca + Mg (mmol l(-1)), Ca, Mg, TDS, Cl, HCO3, SO4, NO3, SiO2 and PO4. The obtained results document the highest relationship between ReI and the groundwater contents of Ca + Mg (mmol l(-1)), Ca and Mg. Following limit values were set for the most significant groundwater chemicals/parameters: Ca + Mg 4.4-7.6 mmol l(-1), Ca > 89.4 mg l(-1) and Mg 42-78.1 mg l(-1). At these concentration ranges, the relative mortality for cardiovascular diseases in the Slovak Republic reaches the lowest levels. These limit values are about twice higher in comparison with the current Slovak valid guideline values for the drinking water.

The UK geochemical environment and cardiovascular diseases: magnesium in food and water

Cardiovascular diseases (CVDs) contribute approximately one-third to noncommunicable diseases in the UK. The central role of magnesium in CVDs (enzyme activity, cardiac signalling, etc.) is well established. Mortality and morbidity rates for CVDs may be inversely related to water hardness, suggesting a role for environmental magnesium. Published official and quasi-official data sources were evaluated to establish a model magnesium intake for a representative adult: standardised reference individual (SRI), standardised reference male (SRM) or standardised reference female (SRF). For typical dietary constituents, only tap water is probably locally derived and bottled water may not be. Fruits and vegetables are imported from many countries, while meat, dairy and cereal products represent a composite of UK source areas. Alcoholic beverages provide magnesium, there is doubt about its absorptive efficiency, and they are not locally derived. A simple model was devised to examine the effect of varying dietary contributions to total daily intake of magnesium. Omitting tap or bottled water, the combined intake, solid food plus alcoholic beverages, is 10.57 mmol Mg (84.5 % RNI) for the SRM and for the SRF, 8.10 mmol Mg (71.7 % RNI). Consumers drinking water derived from reservoirs or rivers, or supplementing it with the purest bottled water, improve their magnesium intake only slightly compared with water containing no magnesium. Choosing bottled water with high magnesium content when the public supply derives from rivers or reservoirs partially satisfies magnesium needs. Real improvement in SRI magnesium nutrition is seen only where water is hard. However, this conclusion cannot be validated until new measurement technologies for body magnesium become available.

Potential health impacts of hard water

In the past five decades or so evidence has been accumulating about an environmental factor, which appears to be influencing mortality, in particular, cardiovascular mortality, and this is the hardness of the drinking water. In addition, several epidemiological investigations have demonstrated the relation between risk for cardiovascular disease, growth retardation, reproductive failure, and other health problems and hardness of drinking water or its content of magnesium and calcium. In addition, the acidity of the water influences the reabsorption of calcium and magnesium in the renal tubule. Not only, calcium and magnesium, but other constituents also affect different health aspects. Thus, the present review attempts to explore the health effects of hard water and its constituents.

Environmental Pathology

Humans are constantly exposed to hazardous pollutants in the environment—for example, in the air, water, soil, rocks, diet, or workplace. Trace metals are important in environmental pathology because of the wide range of toxic reactions and their potential adverse effects on the physiological function of organ systems. Exposures to toxic trace metals have been the subject of numerous environmental and geochemical investigations, and many studies have been published on the acute and/or chronic effects of high-level exposures to these types of agents; however, much fewer data are available concerning the health effects of low-dose chronic exposure to many trace metals. Chronic low-dose exposures to toxic elements such as cadmium and arsenic have been shown to cause these metals to accumulate in tissues over time, leading to multiple adverse effects in exposed individuals.

Contribution of climate and air pollution to variation in coronary heart disease mortality rates in England

There are substantial geographic variations in coronary heart disease (CHD) mortality rates in England that may in part be due to differences in climate and air pollution. An ecological cross-sectional multi-level analysis of male and female CHD mortality rates in all wards in England (1999–2004) was conducted to estimate the relative strength of the association between CHD mortality rates and three aspects of the physical environment - temperature, hours of sunshine and air quality. Models were adjusted for deprivation, an index measuring the healthiness of the lifestyle of populations, and urbanicity. In the fully adjusted model, air quality was not significantly associated with CHD mortality rates, but temperature and sunshine were both significantly negatively associated (p<0.05), suggesting that CHD mortality rates were higher in areas with lower average temperature and hours of sunshine. After adjustment for the unhealthy lifestyle of populations and deprivation, the climate variables explained at least 15% of large scale variation in CHD mortality rates. The results suggest that the climate has a small but significant independent association with CHD mortality rates in England.

Designs for the combination of group- and individual-level data

BACKGROUND

Studies of ecologic or aggregate data suffer from a broad range of biases when scientific interest lies with individual-level associations. To overcome these biases, epidemiologists can choose from a range of designs that combine these group-level data with individual-level data. The individual-level data provide information to identify, evaluate, and control bias, whereas the group-level data are often readily accessible and provide gains in efficiency and power. Within this context, the literature on developing models, particularly multilevel models, is well-established, but little work has been published to help researchers choose among competing designs and plan additional data collection.

METHODS

We review recently proposed "combined" group- and individual-level designs and methods that collect and analyze data at 2 levels of aggregation. These include aggregate data designs, hierarchical related regression, two-phase designs, and hybrid designs for ecologic inference.

RESULTS

The various methods differ in (i) the data elements available at the group and individual levels and (ii) the statistical techniques used to combine the 2 data sources. Implementing these techniques requires care, and it may often be simpler to ignore the group-level data once the individual-level data are collected. A simulation study, based on birth-weight data from North Carolina, is used to illustrate the benefit of incorporating group-level information.

CONCLUSIONS

Our focus is on settings where there are individual-level data to supplement readily accessible group-level data. In this context, no single design is ideal. Choosing which design to adopt depends primarily on the model of interest and the nature of the available group-level data.

Relationship between tap water hardness, magnesium, and calcium concentration and mortality due to ischemic heart disease or stroke in The Netherlands

BACKGROUND

Conflicting results on the relationship between the hardness of drinking water and mortality related to ischemic heart disease (IHD) or stroke have been reported.

OBJECTIVES

We investigated the possible association between tap water calcium or magnesium concentration and total hardness and IHD mortality or stroke mortality.

METHODS

In 1986, a cohort of 120,852 men and women aged 5569 years provided detailed information on dietary and other lifestyle habits. Follow-up for mortality until 1996 was established by linking data from the Central Bureau of Genealogy and Statistics Netherlands. We calculated tap water hardness for each postal code using information obtained from all pumping stations in the Netherlands. Tap water hardness was categorized as soft [< 1.5 mmol/L calcium carbonate (CaCO3)], medium hard (1.62.0 mmol/L CaCO3), and hard (> 2.0 mmol/L CaCO3). The multivariate case-cohort analysis was based on 1,944 IHD mortality and 779 stroke mortality cases and 4,114 subcohort members.

RESULTS

For both men and women, we observed no relationship between tap water hardness and IHD mortality [hard vs. soft water: hazard ratio (HR) = 1.03; 95% confidence interval (CI), 0.851.28 for men and HR = 0.93; 95% CI, 0.711.21 for women) and stroke mortality (hard vs. soft water HR = 0.90; 95% CI, 0.661.21 and HR = 0.86; 95% CI, 0.621.20, respectively). For men with the 20% lowest dietary magnesium intake, an inverse association was observed between tap water magnesium intake and stroke mortality (HR per 1 mg/L intake = 0.75; 95% CI, 0.610.91), whereas for women with the 20% lowest dietary magnesium intake, the opposite was observed.

CONCLUSIONS

We found no evidence for an overall significant association between tap water hardness, magnesium or calcium concentrations, and IHD mortality or stroke mortality. More research is needed to investigate the effect of tap water magnesium on IHD mortality or stroke mortality in subjects with low dietary magnesium intake.

Geographic-based ecological correlation studies using supplemental case-control data

It is well known that the ecological study design suffers from a variety of biases that render the interpretation of its results difficult. Despite its limitations, however, the ecological study design is still widely used in a range of disciplines. The only solution to the ecological inference problem is to supplement the aggregate data with individual-level data and, to this end, Haneuse and Wakefield (Biometrics 2007; 63:128-136) recently proposed a hybrid study design in which an ecological study is supplemented with a sample of case-control data. The latter provides the basis for the control of bias, while the former may provide efficiency gains. Building on that work, we illustrate the use of the hybrid design in the context of a geographical correlation study of lung cancer mortality from the state of Ohio. Focusing on epidemiological applications, we initially provide an overview of the use of ecological studies in scientific research, highlighting the breadth of current application as well as advantages and drawbacks of the design. We consider the interplay between the two sources of information in the design: ecological and case-control, and then provide details on a Bayesian spatial random effects model in the setting of the hybrid design. Issues of specification are addressed, as well as sensitivity to modeling assumptions. Further, an interesting feature of these data is that they provide an example of how the proposed design may be used to resolve the ecological fallacy.

Ecologic Studies Revisited

Ecologic studies use data aggregated over groups rather than data on individuals. Such studies are popular because they use existing databases and can offer large exposure variation if the data arise from broad geographical areas. Unfortunately, the aggregation of data that define ecologic studies results in an information loss that can lead to ecologic bias. Specifically, ecologic bias arises from the inability of ecologic data to characterize within-area variability in exposures and confounders. We describe in detail particular forms of ecologic bias so that their potential impact on any particular study may be assessed. The only way to overcome such bias, while avoiding uncheckable assumptions concerning the missing information, is to supplement the ecologic with individual-level information, and we outline a number of proposals that may achieve this aim.

The Combination of Ecological and Case-Control Data

Ecological studies, in which data are available at the level of the group, rather than at the level of the individual, are susceptible to a range of biases due to their inability to characterize within-group variability in exposures and confounders. In order to overcome these biases, we propose a hybrid design in which ecological data are supplemented with a sample of individual-level case-control data. We develop the likelihood for this design and illustrate its benefits via simulation, both in bias reduction when compared to an ecological study, and in efficiency gains relative to a conventional case-control study. An interesting special case of the proposed design is the situation where ecological data are supplemented with case-only data. The design is illustrated using a dataset of county-specific lung cancer mortality rates in the state of Ohio from 1988.

Calcium and magnesium in drinking water and risk of death from acute myocardial infarction in Taiwan

Many studies have examined the association between cardiovascular disease mortality and water hardness. However, the results have not been consistent. This report examines whether calcium and magnesium in drinking water are protective against acute myocardial infarction (AMI). All eligible AMI deaths (10,094 cases) of Taiwan residents from 1994 to 2003 were compared with deaths from other causes (10,094 controls), and the levels of calcium and magnesium in drinking water of these residents were determined. Data on calcium and magnesium levels in drinking water throughout Taiwan have been obtained from the Taiwan Water Supply Corporation. The control group consisted of people who died from other causes and the controls were pair matched to the cases by sex, year of birth, and year of death. The adjusted odd ratios (95% confidence interval) were 0.79 (0.73-0.86) for the group with water calcium levels between 25.1 and 42.4 mg/L and 0.71 (0.65-0.77) for the group with calcium levels of 42.6 mg/L or more. After adjustment for calcium levels in drinking water, there was no difference between the groups with different levels of magnesium. The results of the present study show that there is a significant protective effect of calcium intake from drinking water on the risk of death from AMI.

Daily Intake of Magnesium and Calcium From Drinking Water in Relation to Myocardial Infarction

BACKGROUND

A decreased risk for cardiovascular disease has been related to the hardness of drinking water, particularly high levels of magnesium. However, the evidence is still uncertain, especially in relation to individual intake from water.

METHODS

We used data from the Stockholm Heart Epidemiology Program, a population-based case-control study conducted during 1992-1994, to study the association between myocardial infarction and the daily intake of drinking water magnesium and calcium. Our analyses are based on 497 cases age 45-70 years, and 677 controls matched on age, sex, and hospital catchment area. Individual data on magnesium, calcium, and hardness of the domestic drinking water were assessed from waterwork registers or analyses of well water.

RESULTS

After adjustment for the matching variables and smoking, hypertension, socioeconomic status, job strain, body mass index, diabetes, and physical inactivity, the odds ratio for myocardial infarction was 1.09 (95% confidence interval = 0.81-1.46) associated with a tap water hardness above the median (>4.4 German hardness degrees) and 0.88 (0.67-1.15) associated with a water magnesium intake above the median (>1.86 mg/d). There was no apparent sign of any exposure-response pattern related to water intake of magnesium or calcium.

CONCLUSIONS

This study does not support previous reports of a protective effect on myocardial infarction associated with consumption of drinking water with higher levels of hardness, magnesium, or calcium.

Spatial epidemiology: current approaches and future challenges

Spatial epidemiology is the description and analysis of geographic variations in disease with respect to demographic, environmental, behavioral, socioeconomic, genetic, and infectious risk factors. We focus on small-area analyses, encompassing disease mapping, geographic correlation studies, disease clusters, and clustering. Advances in geographic information systems, statistical methodology, and availability of high-resolution, geographically referenced health and environmental quality data have created unprecedented new opportunities to investigate environmental and other factors in explaining local geographic variations in disease. They also present new challenges. Problems include the large random component that may predominate disease rates across small areas. Though this can be dealt with appropriately using Bayesian statistics to provide smooth estimates of disease risks, sensitivity to detect areas at high risk is limited when expected numbers of cases are small. Potential biases and confounding, particularly due to socioeconomic factors, and a detailed understanding of data quality are important. Data errors can result in large apparent disease excess in a locality. Disease cluster reports often arise nonsystematically because of media, physician, or public concern. One ready means of investigating such concerns is the replication of analyses in different areas based on routine data, as is done in the United Kingdom through the Small Area Health Statistics Unit (and increasingly in other European countries, e.g., through the European Health and Environment Information System collaboration). In the future, developments in exposure modeling and mapping, enhanced study designs, and new methods of surveillance of large health databases promise to improve our ability to understand the complex relationships of environment to health.

Geochemistry of ground water and the incidence of acute myocardial infarction in Finland

STUDY OBJECTIVE

To examine the association of spatial variation in acute myocardial infarction (AMI) incidence and its putative environmental determinants in ground water such as total water hardness, the concentration of calcium, magnesium, fluoride, iron, copper, zinc, nitrate, and aluminium.

DESIGN

Small area study using Bayesian modelling and the geo-referenced data aggregated into 10 km x 10 km cells.

SETTING

The population data were obtained from Statistics Finland, AMI case data from the National Death Register and the Hospital Discharge Register, and the geochemical data from hydrogeochemical database of Geological Survey of Finland.

PARTICIPANTS

A total of 18 946 men aged 35-74 years with the first AMI attack in the years 1983, 1988, and 1993.

MAIN RESULTS

One unit (in German degree degrees dH) increment in water hardness decreased the risk of AMI by 1%. Geochemical elements in ground water included in this study did not show a statistically significant effect on the incidence and spatial variation of AMI, even though suggestive findings were detected for fluoride (protective), iron and copper (increasing).

CONCLUSIONS

The results of this study with more specific Bayesian statistical analysis confirm findings from earlier observations of the inverse relation between water hardness and coronary heart disease. The role of environmental geochemistry in the geographical variation of the AMI incidence should be studied further in more detail incorporating the individual intake of both food borne and water borne nutrients. Geochemical-spatial analysis provides a basis for the selection of areas suitable for such research.

The influence of calcium and magnesium in drinking water and diet on cardiovascular risk factors in individuals living in hard and soft water areas with differences in cardiovascular mortality

BACKGROUND

The role of water hardness as a risk factor for cardiovascular disease has been widely investigated and evaluated as regards regional differences in cardiovascular disease. This study was performed to evaluate the relation between calcium and magnesium in drinking water and diet and risk factors for cardiovascular disease in individuals living in hard and soft water areas with considerable differences in cardiovascular mortality.

METHODS

A random sample of 207 individuals living in two municipalities characterised by differences in cardiovascular mortality and water hardness was invited for an examination including a questionnaire about health, social and living conditions and diet. Intake of magnesium and calcium was calculated from the diet questionnaire with special consideration to the use of local water. Household water samples were delivered by each individual and were analysed for magnesium and calcium.

RESULTS

In the total sample, there were positive correlations between the calcium content in household water and systolic blood pressure (SBP) and negative correlations with s-cholesterol and s-LDL-cholesterol. No correlation was seen with magnesium content in household water to any of the risk factors. Calcium content in diet showed no correlation to cardiovascular risk factors. Magnesium in diet was positively correlated to diastolic blood pressure (DBP). In regression analyses controlled for age and sex 18.5% of the variation in SBP was explained by the variation in BMI, HbA1c and calcium content in water. Some 27.9% of the variation in s-cholesterol could be explained by the variation in s-triglycerides (TG), and calcium content in water.

CONCLUSIONS

This study of individuals living in soft and hard water areas showed significant correlations between the content of calcium in water and major cardiovascular risk factors. This was not found for magnesium in water or calcium or magnesium in diet. Regression analyses indicated that calcium content in water could be a factor in the complexity of relationships and importance of cardiovascular risk factors. From these results it is not possible to conclude any definite causal relation and further research is needed.

Sensitivity analyses for ecological regression

In many ecological regression studies investigating associations between environmental exposures and health outcomes, the observed relative risks are in the range 1.0-2.0. The interpretation of such small relative risks is difficult due to a variety of biases--some of which are unique to ecological data, since they arise from within-area variability in exposures/confounders. The potential for residual spatial dependence, due to unmeasured confounders and/or data anomalies with spatial structure, must also be considered, though it often will be of secondary importance when compared to the likely effects of unmeasured confounding and within-area variability in exposures/confounders. Methods for addressing sensitivity to these issues are described, along with an approach for assessing the implications of spatial dependence. An ecological study of the association between myocardial infarction and magnesium is critically reevaluated to determine potential sources of bias. It is argued that the sophistication of the statistical analysis should not outweigh the quality of the data, and that finessing models for spatial dependence will often not be merited in the context of ecological regression.

Development of a questionnaire for quantitative assessment in the field of health and human rights

We hypothesize that a human rights framework would be able to analyse central health-related societal issues within important settings like the work place, the family or the health care system. Our study goal was the development and population-based evaluation of a questionnaire for assessment of the perceived human rights status. A questionnaire (HR-14) was developed from the guiding principles of international human rights legislation. For its psychometric evaluation, computer-assisted telephone interviews were conducted in four cities in Europe (Munich, Dresden, Vienna and Bern). Cronbach's alpha for internal consistency was 0.76. Factor analysis supported the concept of human rights as indivisible and interdependent. Extracted factors were consistent with the preliminary settings of family and friends, health care system and community at large, and a supplementary setting workplace. Perceived human rights status was associated with physical function, mental/emotional health, age, study region, general health and employment status. We conclude that it is possible to develop a human rights questionnaire with good psychometric properties. Measurement of the perceived human rights status of populations and population groups may contribute to health policies sensitive to human rights.

Drinking water and cardiovascular disease

A link between cardiovascular disease (CVD) mortality and the hardness of drinking water (DW) is suggested by about 30 epidemiological studies performed worldwide in the general population since 1957. This review examines the main ecological studies, case-control studies and cohort studies, published between 1960 and 2000. Attention is paid to the problem of interpretation of this typical result of environmental epidemiology. Some studies focused on the role played by inorganic elements known as DW contaminants (mainly, As, Pb) and above all on the role of the magnesium content of DW and its cardioprotective effects. To date, it would be impossible to understand this environmental findings without large intervention studies performed in well-controlled public health programs.