A genome-wide association study provides insights into the genetic etiology of 57 essential and non-essential trace elements in humans

Trace elements are important for human health but may exert toxic or adverse effects. Mechanisms of uptake, distribution, metabolism, and excretion are partly under genetic control but have not yet been extensively mapped. Here we report a comprehensive multi-element genome-wide association study of 57 essential and non-essential trace elements. We perform genome-wide association meta-analyses of 14 trace elements in up to 6564 Scandinavian whole blood samples, and genome-wide association studies of 43 trace elements in up to 2819 samples measured only in the Trøndelag Health Study (HUNT). We identify 11 novel genetic loci associated with blood concentrations of arsenic, cadmium, manganese, selenium, and zinc in genome-wide association meta-analyses. In HUNT, several genome-wide significant loci are also indicated for other trace elements. Using two-sample Mendelian randomization, we find several indications of weak to moderate effects on health outcomes, the most precise being a weak harmful effect of increased zinc on prostate cancer. However, independent validation is needed. Our current understanding of trace element-associated genetic variants may help establish consequences of trace elements on human health.

Skogholt's disease-A tauopathy precipitated by iron and copper?

BACKGROUND

It has been suggested that Skogholt's disease is a new neurological disease entity. The disease, confined to a family line in Hedmark county, Norway, usually affects both the brain and peripheral nerves. Typical findings are white matter lesions in the brain, myelin damage in peripheral nerves, and discolored cerebrospinal fluid with high concentrations of protein, copper, and iron. Little is known about the natural progression of the disease and its underlying cause, but the high level of copper and iron in the cerebrospinal fluid may cause or exacerbate inflammation in the central nervous system.

METHODS

The present clinical study further explores the disease progression with clinical chemistry analyses and mass spectrometry of blood and cerebrospinal fluid (CSF) from patients and controls. Findings are corroborated with cognitive assessments.

RESULTS

Pathological changes in CSF with low amyloid-β₄₂ and high levels of tau proteins, total protein, copper, and iron, were discovered among Skogholt patients. The Montreal Cognitive Assessment identified 36 % of the patients as below normal range, while most patients performed slower than the norm mean time on the Trail Making Test. Mini-Mental Status Examination disclosed only minor deviations.

CONCLUSION

The findings in the present study strengthen our initial suggestion that Skogholt's disease most likely is a new neurological disorder and provide new clues to its cause: The disease may belong to the family of neurodegenerative disorders termed tauopathies. The increased level of copper and iron may contribute to neuroinflammation as these metals also have been associated with other neurodegenerative disorders. Although the causes of neurodegenerative disorders are currently largely unknown, studies on rare disease entities, such as the present one, may increase the understanding of neurodegeneration in general.

Trace elements in whole blood in the general population in Trøndelag County, Norway: The HUNT3 Survey

BACKGROUND

Biomonitoring of a cohort within a large health survey can provide reliable information on trace element status. The main aims of this study were 1) to determine the concentrations of 28 trace elements in whole blood samples from the general population of the Nord-Trøndelag region, Norway, and 2) to investigate how trace element concentrations vary with geographical area, lifestyle, and socio-demographic factors.

METHODS

Whole blood samples were collected in the third survey of the Trøndelag Health Survey (HUNT3), a large population-based study in Norway. In total, 1011 whole blood samples from individuals aged 20-91 years were analyzed using high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). We compared trace element concentrations (As, B, Be, Br, Ca, Cd, Cr, Cs, Cu, Ga, Au, In, Fe, Pb, Hg, Tl, Mg, Mn, Mo, Ni, Rb, Sc, Se, Ag, Sr, Sn, W and Zn) between three geographical areas (coastal, fjord/town, inland/mountain) using multivariable linear regression and assessed differences in trace element concentrations with socio-demographic and lifestyle factors using general linear models.

RESULTS

Trace element concentrations were generally comparable to levels reported in other recent studies and suggest low exposure to toxic trace elements in the region. We found geographical differences in concentrations of 19 trace elements. As, Br, Hg, and Se concentrations were higher on the coast compared to the fjord/town and inland/mountain areas, suggesting that the marine environment is an important source of exposure for these trace elements. In addition, socio-demographic and lifestyle characteristics, particularly age and sex, were associated with differences in trace element concentrations.

CONCLUSIONS

We report concentrations of 28 trace elements in the general population of a rural region with low exposure to pollution. Whole blood concentrations of trace elements varied with geographical area, the participants' lifestyle, and socio-demographic characteristics, highlighting the importance of considering these factors when evaluating trace element status in a population.

Trace Elements in the Large Population-Based HUNT3 Survey

The Nord-Trøndelag Health Study (The HUNT Study) is a large health survey population study in the county of Trøndelag, Norway. The survey has been repeated four times in about 10-year intervals. In the HUNT3 survey (2006-2008), we collected 28,000 samples for trace element analysis. Blood samples from 758 healthy persons without known occupational exposure were selected for multielement analysis of a small sample of blood (0.25 mL). The aim of the study was to determine the minimum blood volume that can be used for the analytical procedure and to compare our results with previously published results of similar surveys in healthy populations. Samples were digested and the concentration of selected trace elements was determined by ICP-MS. We report results on essential elements (B, Co, Cu, Mn, Se and Zn) as well as non-essential elements (As, Be, Br, Cd, Cs, In, La, Pb, Hg, Nd, Ni, Nb, Pd, Pt, Sm, Ta and Sn). Results are similar to previous studies on the HUNT3 population, and with a few exceptions, our data compares very well with results obtained in recent studies from other countries. We wanted to test a minimum volume of blood in a large-scale analytical program. For a number of nonessential elements, our results were below the limit of detection. We suggest that future studies using similar ICP-MS equipment as analytical tool should use at least 0.5 mL of blood.

Essential trace elements in Norwegian obese patients before and 12 months after Roux-en-Y gastric bypass surgery: Copper, manganese, selenium and zinc

OBJECTIVES

The objective of the present study was to assess trace element status in morbidly obese subjects before and one year after Roux-en-Y gastric bypass (RYGB) in order to identify possible deficiencies.

METHODS

The study population included 46 patients in the age range 27-59 years, the majority (85 %) were women. The enrolled patients attended an eight week course on lifestyle changes before bariatric surgery. After RYGB they were recommended daily micronutrient supplements with a commonly used multivitamin-mineral tablet in addition to intramuscular vitamin B₁₂ injections (1 mg) every third month for 12 months. Whole blood concentrations of Cu, Mn, Se and Zn were determined using high resolution inductively coupled plasma mass spectrometry.

RESULTS

During the 12 months follow up after bariatric surgery, the patients had lost mean 32.3 kg and median whole blood concentrations of Cu (-16 %) were reduced, Mn (+14 %) and Zn (+6%) were increased, while the Se values were essentially unchanged. Compared with reference ranges, median postoperative concentrations of all essential trace elements were either below (Zn) or in the lower reference range (Cu, Mn, Se).

CONCLUSION

Essential trace elements were below or in the lower reference range twelve months after RYGB. Our results indicate a need for updated guidelines in Nordic countries for trace metal monitoring and supplements in patients after bariatric surgery, especially when gastric bypass surgery is used. Further studies are required to explore and prevent trace element deficiency related to obesity and bariatric surgery.

Cadmium, lead and mercury in Norwegian obese patients before and 12 months after bariatric surgery

PURPOSE

Previous studies have suggested a role for the toxic elements lead (Pb), mercury (Hg) and cadmium (Cd) in the development of insulin resistance and hypertension. Increased blood Pb levels have been reported after bariatric surgery and weight loss. As about 80% of patients undergoing bariatric surgery are women, most of them of childbearing age, there are concerns regarding fetal exposure to toxic trace elements. We measured whole blood Hg, Pb and Cd concentrations in morbidly obese patients before and 12 months after Roux-en-Y gastric bypass (RYGB).

PATIENTS AND METHODS

Forty-six patients eligible for bariatric surgery were recruited at Innlandet Hospital Trust, Norway (2012-2014). The majority were women and 54% were of reproductive age. Whole blood samples were collected prior to and 12 months after surgery. Trace element concentrations were measured using mass spectrometry (HR-ICP-MS).

RESULTS

Median whole blood Pb concentrations increased by 73% during the 12 months study period while Hg and Cd decreased by 31% and 27%, respectively. We found a negative correlation between Pb levels before surgery and BMI (p = 0.02). Before surgery patients with hypertension had significantly higher median whole blood Hg levels compared to patients with normal blood pressure (p < 0.001).

CONCLUSION

One year after bariatric surgery, the median whole blood Pb concentration was increased, while Hg and Cd concentrations were decreased. The majority of bariatric surgery patients are women of reproductive age and weight loss is associated with improved fertility. As even low dose Pb exposure during fetal life is associated with negative effects on the central nervous system, the observed increase in whole blood Pb after weight loss causes concern. Further studies are needed to elucidate these observations.

Trace element status in patients with type 2 diabetes in Norway: The HUNT3 Survey

Several epidemiological studies have indicated that a number of trace elements may play a role in type 2 diabetes (T2D). We investigated the association between prevalent T2D and the concentrations of 25 trace elements in whole blood, and the relationships between T2D duration and blood levels of the trace elements that we found to be related to T2D prevalence. In this population based case-control study, 267 patients with self-reported T2D and 609 controls (frequency matched), were selected from the third Nord-Trøndelag Health Survey. Trace element blood levels were determined by high resolution inductively coupled plasma-mass spectrometry. Multivariable conditional logistic regression and multivariable linear regression were used to estimate associations. The prevalence of T2D was positively associated with boron, calcium and silver, and inversely associated with indium, lead and magnesium (P_trend<0.05). We found no statistical evidence for associations between blood levels of arsenic, bromine, cadmium, cesium, chromium, copper, gallium, gold, manganese, mercury, molybdenum, nickel, rubidium, selenium, strontium, tantalum, thallium, tin and zinc and T2D prevalence. After corrections for multiple testing, associations remained significant for calcium and lead (Q_trend<0.05), and borderline significant for magnesium, silver and boron. With increasing disease duration, higher calcium levels were observed (P<0.05). This study suggests an association between prevalent T2D and blood levels of boron, calcium, indium, lead, magnesium and silver.

Evaluation of Macro- and Microelement Levels in Black Tea in View of Its Geographical Origin

The aim of this study was to evaluate the elemental composition of black tea samples and their infusions in view of their geographical origin. In total, 14 elements were analyzed, 13 (Ca, K, Mg, Na, Mn, Fe, Zn, Cu, Cr, Ni, Co, Cd, and Pb) by flame atomic absorption spectrometry, and P by UV-Vis spectrometry, after mineralization of samples. It was found that K was the most abundant macroelement in the analyzed samples, whereas among microelements, the highest concentration was found for Mn. Based on the obtained data, the percentage of elements leached into the infusions as well as the daily elemental intake from tea were calculated. The daily intake from tea was compared to the recommended daily allowances (RDAs), and the highest percentages of the RDAs were found for Mn (15 %) and Co (10 %). To study the relations between elemental composition and country of origin of samples, factor analysis and cluster analysis were applied. These multivariate techniques proved to be efficient tools able to differentiate samples according to their provenance as well as plantation within the common regions.

Trace elements in early phase type 2 diabetes mellitus-A population-based study. The HUNT study in Norway

Differences in trace elements levels between individuals with type 2 diabetes and controls have been reported in several studies in various body fluids and tissues, but results have been inconsistent. In order to examine trace element levels in the early phase of type 2 diabetes, we investigated the association between whole blood levels of 26 trace elements and the prevalence of previously undiagnosed, screening-detected type 2 diabetes. The study was conducted as a case-control study nested within the third survey of the population-based Nord-Trøndelag Health Study (HUNT3 Survey). Among participants without previously known diabetes, 128 cases of type 2 diabetes were diagnosed in people with a high diabetes risk score (FINDRISC≥15), and frequency-matched for age and sex with 755 controls. Blood samples were analyzed by high resolution inductively coupled plasma mass spectrometry. Associations between trace element levels and the prevalence of previously undiagnosed type 2 diabetes were evaluated with multivariable conditional logistic regression controlling for age, sex, body mass index, waist-to-hip ratio, education, income, smoking and family history of diabetes. The prevalence of previously undiagnosed type 2 diabetes increased across tertiles/quartiles for cadmium, chromium, iron, nickel, silver and zinc, and decreased with increasing quartiles of bromine (P_trend<0.05). After corrections for multiple testing, associations for chromium remained significant (Q_trend<0.05), while associations for iron and silver were borderline significant. No associations were found for arsenic, boron, calcium, cesium, copper, gallium, gold, indium, lead, magnesium, manganese, mercury, molybdenum, rubidium, selenium, strontium, tantalum, thallium and tin. Our results suggest a possible role of bromine, cadmium, chromium, iron, nickel, silver and zinc in the development of type 2 diabetes.

Multi-element analysis of airborne particulate matter from different work tasks during subsea tunnel rehabilitation work

Tunnel rehabilitation work involves exposure to various air contaminants, including airborne particulate matter (APM). Little is known on the contents of different chemical components of APM generated during tunnel work. The objective of the present study was to characterize exposure to APM and various elements for different job categories in different size fractions of APM during a subsea tunnel rehabilitation project carried out in Western Norway. Personal as well as stationary samples of inhalable, thoracic and respirable dust were collected from workers divided into 11 different job categories based on work operations performed, and air concentrations of a range of elements were determined using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). Overall, APM concentrations were low, but with some measurements exceeding the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) for inhalable particles, and considerable proportions of respirable and especially inhalable APM exceeding 10% of the TLVs. For most elements, air concentrations measured were quite low, in the ng/m(3) range, except for the major crustal elements Si, Fe, Al, and Mg, which were found to be in the µg/m(3) range. Asphalt millers overall had the highest exposure levels for APM and most measured elements; for instance, mean concentrations of V, Rb, and Mn were 380, 210, and 2000 ng/m(3) in inhalable and 33, 44, and 310 ng/m(3) in respirable APM. Mounting PVC membrane seemed to generate elevated levels of Cr, Zn, Sn, Pb, Sb, As, Mn, Fe, and Ni, whereas typical bedrock elements were elevated during drilling activities compared to the low exposed categories lead car drivers, foremen/surveyors, drivers of heavy-duty vehicles, and electricians. Overall, stationary samples contained lower amounts of dust and elemental constituents compared to personal samples. Elemental air concentrations were highly variable with occasional elevated values for APM and certain elements, particularly Cr and Zn.

Population data on calcium in drinking water and hip fracture: An association may depend on other minerals in water. A NOREPOS study

BACKGROUND

The Norwegian population has among the highest hip fracture rates in the world. The incidence varies geographically, also within Norway. Calcium in drinking water has been found to be beneficially associated with bone health in some studies, but not in all. In most previous studies, other minerals in water have not been taken into account. Trace minerals, for which drinking water can be an important source and even fulfill the daily nutritional requirement, could act as effect-modifiers in the association between calcium and hip fracture risk. The aim of the present study was to investigate the association between calcium in drinking water and hip fracture, and whether other water minerals modified this association.

MATERIALS AND METHODS

A survey of trace metals in 429 waterworks, supplying 64% of the population in Norway, was linked geographically to the home addresses of patients with incident hip fractures (1994-2000). Drinking water mineral concentrations were divided into "low" (below and equal waterworks average) and "high" (above waterworks average). Poisson regression models were fitted, and all incidence rate ratios (IRRs) were adjusted for age, geographic region, urbanization degree, type of water source, and pH of the water. Effect modifications were examined by stratification, and interactions between calcium and magnesium, copper, zinc, iron and manganese were tested both on the multiplicative and the additive scale. Analyses were stratified on gender.

RESULTS

Among those supplied from the 429 waterworks (2,110,916 person-years in men and 2,397,217 person-years in women), 5433 men and 13,493 women aged 50-85 years suffered a hip fracture during 1994-2000. Compared to low calcium in drinking water, a high level was associated with a 15% lower hip fracture risk in men (IRR=0.85, 95% CI: 0.78, 0.91) but no significant difference was found in women (IRR=0.98, 95%CI: 0.93-1.02). There was interaction between calcium and copper on hip fracture risk in men (p=0.051); the association between calcium and hip fracture risk was stronger when the copper concentration in water was high (IRR=0.52, 95% CI: 0.35, 0.78) as opposed to when it was low (IRR=0.88, 95% CI: 0.81, 0.94). This pattern persisted also after including potential confounding factors and other minerals in the model. No similar variation in risk was found in women.

CONCLUSION

In this large, prospective population study covering two thirds of the Norwegian population and comprising 19,000 hip fractures, we found an inverse association between calcium in drinking water and hip fracture risk in men. The association was stronger when the copper concentration in the water was high.

Iron and copper in progressive demyelination--New lessons from Skogholt's disease

The pathophysiological mechanisms of progressive demyelinating disorders including multiple sclerosis are incompletely understood. Increasing evidence indicates a role for trace metals in the progression of several neurodegenerative disorders. The study of Skogholt disease, a recently discovered demyelinating disease affecting both the central and peripheral nervous system, might shed some light on the mechanisms underlying demyelination. Cerebrospinal fluid iron and copper concentrations are about four times higher in Skogholt patients than in controls. The transit into cerebrospinal fluid of these elements from blood probably occurs in protein bound form. We hypothesize that exchangeable fractions of iron and copper are further transferred from cerebrospinal fluid into myelin, thereby contributing to the pathogenesis of demyelination. Free or weakly bound iron and copper ions may exert their toxic action on myelin by catalyzing production of oxygen radicals. Similarities to demyelinating processes in multiple sclerosis and other myelinopathies are discussed.

The neurotoxicity of iron, copper and manganese in Parkinson's and Wilson's diseases

Impaired cellular homeostasis of metals, particularly of Cu, Fe and Mn may trigger neurodegeneration through various mechanisms, notably induction of oxidative stress, promotion of α-synuclein aggregation and fibril formation, activation of microglial cells leading to inflammation and impaired production of metalloproteins. In this article we review available studies concerning Fe, Cu and Mn in Parkinson's disease and Wilson's disease. In Parkinson's disease local dysregulation of iron metabolism in the substantia nigra (SN) seems to be related to neurodegeneration with an increase in SN iron concentration, accompanied by decreased SN Cu and ceruloplasmin concentrations and increased free Cu concentrations and decreased ferroxidase activity in the cerebrospinal fluid. Available data in Wilson's disease suggest that substantial increases in CNS Cu concentrations persist for a long time during chelating treatment and that local accumulation of Fe in certain brain nuclei may occur during the course of the disease. Consequences for chelating treatment strategies are discussed.

Essential and non-essential elements in natural vegetation in southern Norway: contribution from different sources

Concentrations of essential and non-essential elements in five widespread species of natural boreal vegetation were studied with respect to seasonal variation and contribution from different sources. The plant species included in the study were Betula pubescens, Sorbus aucuparia, Vaccinium myrtillus, Vaccinium uliginosum, Calluna vulgaris and Deschampsia flexuosa. Concentrations of elements essential to plants remained essentially constant or decreased slightly throughout the growing season. Concentrations of most non-essential elements increased or tended to increase on a dry mass basis from June to July as well as from July to September. The increasing trend for these elements was observed for all species except C. vulgaris. Principal component analysis (PCA) of the material indicated a common source for many of the non-essential elements; Sc, Ti, V, Ga, As, Y, Sb, lanthanides, Pb, Bi, and U, i.e. both elements presumably of geogenic origin and elements associated with trans-boundary air pollution. Uptake by plant roots appeared to be the main source of nutrient elements as well as some non-essential elements.

Do cadmium, lead, and aluminum in drinking water increase the risk of hip fractures? A NOREPOS study

The aim of this study was to investigate relations between cadmium, lead, and aluminum in municipality drinking water and the incidence of hip fractures in the Norwegian population. A trace metals survey in 566 waterworks was linked geographically to hip fractures from hospitals throughout the country (1994-2000). In all those supplied from these waterworks, 5,438 men and 13,629 women aged 50-85 years suffered a hip fracture. Poisson regression models were fitted, adjusting for age, region of residence, urbanization, and type of water source as well as other possibly bone-related water quality factors. Effect modification by background variables and interactions between water quality factors were examined (correcting for false discovery rate). Men exposed to a relatively high concentration of cadmium (IRR = 1.10; 95 % CI 1.01, 1.20) had an increased risk of fracture. The association between relatively high lead and hip fracture risk was significant in the oldest age group (66-85 years) for both men (IRR = 1.11; 95 % CI 1.02, 1.21) and women (IRR = 1.10; 95 % CI 1.04, 1.16). Effect modification by degree of urbanization on hip fracture risk in men was also found for all three metals: cadmium, lead, and aluminum. In summary, a relatively high concentration of cadmium, lead, and aluminum measured in drinking water increased the risk of hip fractures, but the associations depended on gender, age, and urbanization degree. This study could help in elucidating the complex effects on bone health by risk factors found in the environment.

Nationwide data on municipal drinking water and hip fracture: could calcium and magnesium be protective? A NOREPOS study

Norway has a high incidence of hip fractures, and the incidence varies by degree of urbanization. This variation may reflect a difference in underlying environmental factors, perhaps variations in the concentration of calcium and magnesium in municipal drinking water. A trace metal survey (1986-1991) in 556 waterworks (supplying 64% of the Norwegian population) was linked geographically to hip fractures from hospitals throughout the country (1994-2000). In all, 5472 men and 13,604 women aged 50-85years suffered a hip fracture. Poisson regression models were fitted, adjusting for age, urbanization degree, region of residence, type of water source, and pH. The concentrations of calcium and magnesium in drinking water were generally low. An inverse association was found between concentration of magnesium and risk of hip fracture in both genders (IRR men highest vs. lowest tertile=0.80, 95% CI: 0.74, 0.87; IRR women highest vs. lowest tertile=0.90, 95% CI: 0.85, 0.95), but no consistent association between calcium and hip fracture risk was observed. The highest tertile of urbanization degree (city), compared to the lowest (rural), was related to a 23 and 24% increase in hip fracture risk in men and women, respectively. The association between magnesium and hip fracture did not explain the variation in hip fracture risk between city and rural areas. Magnesium in drinking water may have a protective role against hip fractures; however this association should be further investigated.

Metal concentrations in cerebrospinal fluid and blood plasma from patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal degenerative disorder of motor neurons. The cause of this degeneration is unknown, and different causal hypotheses include genetic, viral, traumatic and environmental mechanisms. In this study, we have analyzed metal concentrations in cerebrospinal fluid (CSF) and blood plasma in a well-defined cohort (n = 17) of ALS patients diagnosed with quantitative electromyography. Metal analyses were performed with high-resolution inductively coupled plasma mass spectrometry. Statistically significant higher concentrations of manganese, aluminium, cadmium, cobalt, copper, zinc, lead, vanadium and uranium were found in ALS CSF compared to control CSF. We also report higher concentrations of these metals in ALS CSF than in ALS blood plasma, which indicate mechanisms of accumulation, e.g. inward directed transport. A pattern of multiple toxic metals is seen in ALS CSF. The results support the hypothesis that metals with neurotoxic effects are involved in the pathogenesis of ALS.

Is the quality of drinking water a risk factor for self-reported forearm fractures? Cohort of Norway

SUMMARY

Compared to pH ≥7.0 in Norwegian municipal drinking water, pH <7.0 increased the risk of forearm fractures in the population-based Cohort of Norway (CONOR; n = 127,272). The association was attenuated (p > 0.05) after adjustments for indicators of bacteria and organic matter, which may signify an association between poor drinking water and bone health.

INTRODUCTION

The Norwegian population has the highest rate of fractures ever reported. A large variation in fracture rate both between and within countries indicates that an environmental factor, such as the quality of drinking water, could be one of the causes of the disparities. Our aim was to investigate a possible association between pH (an important parameter for water quality) and self-reported forearm fracture and to examine whether other water quality factors could account for this association.

METHODS

Using Geographic Information Systems, information on the quality of drinking water was linked to CONOR (n = 127,272; mean age, 50.2 ± 15.8 years), a database comprising ten regional epidemiological health surveys from across the country in the time period 1994-2003.

RESULTS

The highest risk of forearm fracture was found at a pH of around 6.75, with a decreasing risk toward both higher and lower pH values. The increased adjusted odds of forearm fracture in men consuming municipal drinking water with pH <7.0 compared to water with pH ≥7.0 was odds ratio (OR) = 1.19 (95 % CI, 1.14, 1.25), and the corresponding increased odds in women was OR = 1.14 (95 % CI, 1.08, 1.19). This association was attenuated (p > 0.05) after further adjustments for other water quality factors (color grade, intestinal enterococci, and Clostridium perfringens).

CONCLUSIONS

Our findings indicate a higher risk of fracture when consuming water of an acidic pH; however, the risk does not only seem to be due to the acidity level per se, but also to other aspects of water quality associated with pH.

Dementia in the National Cause of Death Registry in Norway 1969-2010

<p><em><strong>Background</strong></em>: The prevalence of dementia is expected to increase markedly during the coming decades. Epidemiological studies involving the National Cause of Death Registry (NCDR) may be useful for exploring the aetiology of dementia. We therefore wanted to study developments in the reporting of dementia in the NCDR over the last four decades.</p><p><em><strong>Methods</strong></em>: We calculated the age- and gender specific proportion of deaths with dementia reported in the NCDR (dementia deaths) in the period 1969-2010, and the proportion of vascular dementia and Alzheimer’s disease deaths in 1986-2010. Separate analyses were done for deaths occurring in nursing homes in 1996-2010. The proportion of dementia deaths where dementia was coded as underlying cause of death was also calculated.</p><p><em><strong>Results:</strong></em> The proportion of dementia deaths increased more than threefold in the period 1969-2010 among women (from 4% to 15%), and more than doubled among men (from 3% to 7%). In nursing homes the proportion increased from 17% to 26% for women and from 13% to 18% for men. The proportion of dementia deaths with Alzheimer’s disease reported in the NCDR increased from practically zero in 1986 to a maximum of 28% in 2005. The proportion of dementia deaths with dementia as underlying cause of death increased from a minimum of 6% in 1972 to a maximum of 51% in 2009.</p><p><em><strong>Conclusion:</strong></em> Although the reporting of dementia in the NCDR increased markedly from 1969 to 2010, dementia is still under-reported for old people and for deaths occurring in nursing homes when compared to prevalence estimates.</p>

Manganese in cerebrospinal fluid and blood plasma of patients with amyotrophic lateral sclerosis

Neurotoxic properties of manganese (Mn) are well documented. It is less known that Mn contributes to the development of neurodegenerative disorders in the general population. This study presents Mn data from patients with amyotrophic lateral sclerosis (ALS) in a well-defined cohort diagnosed by electrophysiological methods. Cerebrospinal fluid (CSF) and plasma were collected from patients and controls. Mn concentrations were analyzed by high-resolution inductively coupled plasma mass spectrometry. Concentrations of Mn were significantly higher in ALS CSF (median 5.67 μg/L) than in CSF from controls (median 2.08 μg/L). Also, ALS CSF Mn concentrations were higher than ALS plasma Mn concentrations (median 0.91 μg/L), suggesting transport of Mn into the central nervous system. The properties of barrier systems between blood and the brain are discussed and the possibility of Mn accumulation contributing to the relentless course of ALS is introduced.

Iron mobilization using chelation and phlebotomy

Knowledge of the basic mechanisms involved in iron metabolism has increased greatly in recent years, improving our ability to deal with the huge global public health problems of iron deficiency and overload. Several million people worldwide suffer iron overload with serious clinical implications. Iron overload has many different causes, both genetic and environmental. The two most common iron overload disorders are hereditary haemochromatosis and transfusional siderosis, which occurs in thalassaemias and other refractory anaemias. The two most important treatment options for iron overload are phlebotomy and chelation. Phlebotomy is the initial treatment of choice in haemochromatosis, while chelation is a mainstay in the treatment of transfusional siderosis. The classical iron chelator is deferoxamine (Desferal), but due to poor gastrointestinal absorption it has to be administered intravenously or subcutaneously, mostly on a daily basis. Thus, there is an obvious need to find and develop new effective iron chelators for oral use. In later years, particularly two such oral iron chelators have shown promise and have been approved for clinical use, namely deferiprone (Ferriprox) and deferasirox (Exjade). Combined subcutaneous (deferoxamine) and oral (deferiprone) treatment seems to hold particular promise.

Beskytter røyking mot Parkinsons sykdom

 SAMMENDRAGDen negative sammenhengen mellom røyking og Parkinsons sykdom i epidemiologiske studier er robust.Det er prosentvis færre røykere og eks-røykere blant Parkinson-pasienter enn blant kontrollpersoner.Videre har røykere en lavere insidens og en lavere dødelighet enn andre av Parkinsons sykdom. Det er etåpent spørsmål om dette skyldes en beskyttende virkning av nikotin eller andre stoffer i tobakksrøyk somhydrazin eller karbonmonoksid, eller om det skyldes andre, underliggende faktorer. De mest aktuelle slikefaktorer er (1) selektiv dødelighet, altså at mange røykere ikke overlever lenge nok til å utvikleParkinsons sykdom, og (2) at personer som utvikler Parkinsons sykdom ofte har karaktertrekk som gjørdet mindre sannsynlig at de begynner å røyke. Det vitenskapelige grunnlaget er i alle fall for tynt for åanbefale røyking som et forebyggende virkemiddel mot Parkinsons sykdom. Og selv om det skulle viseseg at røyking virkelig beskytter mot sykdommen, veier de negative helsevirkningene av røyking myetyngre i folkehelsesammenheng. Allikevel bør denne assosiasjonen forfølges videre, ikke minst forpotensialet for en bedret forståelse av de underliggende patofysiologiske mekanismene bak sykdommen.Flaten TP. Does smoking protect against Parkinson’s disease? Nor J Epidemiol 1995; 5 (2): 145-150. ENGLISH SUMMARYIt is epidemiologically well established that Parkinson's disease is about twice as common among nonsmokers as among smokers. Whether this is due to a protective effect of nicotine or other compounds in cigarette smoke like hydrazine or carbon monoxide, or whether it is due to some other, confounding factor(s), remains to be established. The most relevant confounding factors are (1) selective mortality, that is, many smokers do not survive long enough to develop Parkinson's disease, and (2) that persons who eventually develop Parkinson's disease tend to have a preclinical personality type that makes them less likely to pick up the smoking habit. In any case, the scientific basis is not strong enough to recommend smoking as a preventive strategy in Parkinson's disease. And even if it were clearly demonstrated that smoking protects against the disease, the known adverse effects of smoking are so serious that any beneficial effects on Parkinson's disease could not possibly compensate for this hazard. However, unraveling the mechanism behind the reduced risk of Parkinson's disease in smokers may provide clues to an improved understanding of the pathophysiological mechanisms behind the disease.

Trace elements in cerebrospinal fluid and blood from patients with a rare progressive central and peripheral demyelinating disease

A hereditary neurological disease in a family in Norway has been reported recently. The disease, which we refer to as Skogholt's disease, is a demyelinating disorder of both the central and the peripheral nervous system with adult onset. We investigated whether changes in trace element concentrations could play a role in Skogholt's disease. Using high resolution inductively coupled plasma mass spectrometry, we determined 31 elements in cerebrospinal fluid (CSF), blood plasma and whole blood from these patients, multiple sclerosis patients and a control group. More than threefold increased levels of Cu and Fe, and a twofold increase in Zn were found in the CSF of Skogholt patients compared to controls. Several other significant differences in trace element levels were also found. The increased levels of Cu and Fe in CSF may indicate an active role of these metals in the pathogenesis of Skogholt's disease. Apparently, these metal ions are transferred into the CSF through their protein chelation, as raised protein levels were also seen. We suggest that redistribution of metals from transport proteins into vulnerable sites in the central (and peripheral) nervous system may initiate critical lesions.

Leaching of trace elements from biological tissue by formalin fixation

In studies of trace elements in biological tissue, it is imperative that sample handling does not substantially change element concentrations. In many cases, fresh tissue is not available for study, but formalin-fixed tissue is. Formalin fixation has the potential to leach elements from the tissue, but few studies have been published in this area. The concentrations of 19 elements were determined by high-resolution inductively coupled plasma mass spectrometry in formalin in which human and rat brain samples had been stored for different time durations ranging from weeks up to several years. Additional analysis was carried out in fixed brain samples. There was substantial leaching of elements from the tissue into the formalin, and the leaching varied considerably between different elements. For example, formalin concentrations of As, Cd, Mg, Rb, and Sb increased more than 100-fold upon long-term (years) storage, while for Ni and Cr, the leaching was negligible. The degree of leaching was strongly time-dependent. In conclusion, formalin fixation and storage of biological tissue has the potential to leach substantial fractions of several trace elements from the tissue. The potential of leaching must be critically considered when using formalin-fixed biological tissue in trace metal analysis.

Trace element profiles in single strands of human hair determined by HR-ICP-MS

Trace element analysis of human hair has the potential to reveal retrospective information about an individual's nutritional status and exposure. As trace elements are incorporated into the hair during the growth process, longitudinal segments of the hair may reflect the body burden during the growth period. We have evaluated the potential of human hair to indicate exposure or nutritional status over time by analysing trace element profiles in single strands of human hair. The hair strands from five healthy and occupationally unexposed subjects were cut into 1-cm long segments starting from the scalp. By using high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS), we achieved profiles of 12 elements in single strands of human hair, namely, Ag, As, Au, Cd, Cu, Hg, Fe, Pb, Se, Sr, U and Zn. We have shown that trace element analysis along single strands of human hair can yield information about essential and toxic elements, and for some elements, can be correlated with seasonal changes in diet and exposure. The information obtained from the trace element profiles of human hair in this study substantiates the potential of hair as a biomarker.

Separation of proteins including metallothionein in cerebrospinal fluid by size exclusion HPLC and determination of trace elements by HR-ICP-MS

A method to study the protein binding patterns of trace elements in human cerebrospinal fluid (CSF) is described. Proteins in CSF samples were separated by size exclusion chromatography combined with high performance liquid chromatography (SEC-HPLC). The column was calibrated to separate proteins in the molecular weight range 6-70 kDa. Fractions were then analyzed off-line for trace elements using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). We were able to accurately determine more than 10 elements of clinical interest in the CSF fractions. Results are presented for Cd, Mn, Fe, Pb, Cu and Zn. The total concentrations of 16 trace elements in human plasma and CSF are also presented. The method was able to differentiate the relative contribution of metallothionein and other proteins towards metal binding in human CSF.

Hereditary iron and copper deposition: diagnostics, pathogenesis and therapeutics

Hereditary deposition of iron (primary haemochromatosis) or copper (Wilson's disease) are autosomal recessive metabolic disease characterized by progressive liver pathology and subsequent involvement of various other organs. The prevalence of primary haemochromatosis is approximately 0.5%, about 200 times higher than the prevalence of Wilson's disease. The two diseases are characterized by homozygous occurrences of mutations in the HFE gene on chromosome 6 (primary haemochromatosis) and the ATP7B gene on chromosome 13 (Wilson's disease). Unlike most other inherited conditions, these diseases can be successfully treated, emphasizing the importance of early diagnosis. Serum ferritin values, transferrin saturation and genetic analysis are used when diagnosing haemochromatosis. The diagnostics of Wilson's disease depends on the use of urinary copper values, serum ceruloplasmin and liver biopsy. If untreated, both of these genetic diseases result in rapidly progressing multiorgan damage and early death. The key treatment for haemochromatosis is phlebotomy, for Wilson's disease chelation or Zn treatment. Although the present treatments considerably improve the prognosis of patients, they may be inadequate in patients diagnosed so late that extensive body deposits of metal have been developed. The main research needs in this field are to further clarify molecular mechanisms of disease progression and to develop new chelators that are more effective and less toxic than those presently available.

Performance Study of Diffusive Gradients in Thin Films for 55 Elements

The technique of diffusive gradients in thin films (DGT) is a fairly new and useful tool for in situ measurements of labile metal ions in water. The applicability of DGTs was investigated by comparing independently determined or estimated diffusion coefficients with DGT effective diffusion coefficients (D(DGT)) for 55 elements. The DGTs were exposed at a controlled fluid velocity of 0.1 m s(-1) and a concentration of 1 ng mL(-1) at four pH levels between 4.7 and 6.0, and the D(DGT) values were determined from the uptake by the sampler. The measured D(DGT) values for the elements Co, Ni, Cu, Zn, Cd, Pb, Al, Mn, and Ga were close to previously published values with some deviations for Pb and Zn. The uptake of V, Cr, Fe, U, Mo, Ti, Ba, and Sr varied with pH, and there were some experimental problems that require further investigations. A novel set of D(DGT) values for the lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb, Yb, Lu, Y) was established. The D(DGT) values for these were about 10-15% lower than for free ions in water and indicate that diffusion coefficients of metal ions in the agarose polyacrylamide diffusive hydrogel are 10-15% lower than in water. The high consistency of the data for the lanthanides establishes these elements as new performance test metals for the DGT sampler. The accumulation of the elements Li, Na, K, Rb, Mg, Ca, B, Tl, P, S, As, Bi, Se, Si, Sn, Sb, Te, Zr, Nb, Hf, Ta, W, Th, and Ag was low (D(DGT) lower than 10% of theoretical values). A more efficient elution procedure using concentrated nitric acid for the absorbent gel was established, with elution efficiencies between 95 and 100% for most metals. For deployment times of 24 h, detection limits from 0.001 to 1 ng mL(-1) were achieved with moderate precautions to prevent contamination.

Concentrations of Cd, Co, Cu, Fe, Mn, Rb, V, and Zn in formalin-fixed brain tissue in amyotrophic lateral sclerosis and Parkinsonism-dementia complex of Guam determined by High-resolution ICP-MS

Amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia complex (PDC) are neurodegenerative disorders that occurred with extremely high frequency among the native population on Guam, especially in the 1950s and 1960s, but have substantially declined over the last half-century. The etiology of these diseases is unknown, but the most plausible hypothesis centers on imbalances in essential and toxic metals. We have determined the concentrations of Cd, Co, Cu, Fe, Mn, Rb, V, and Zn in formalin-fixed brain tissue collected during the period 1979-1983 from eight Guamanian patients with ALS, four with PDC, and five control subjects using high-resolution inductively coupled plasma-mass spectrometry. The concentrations of Cd are markedly and significantly elevated both in gray and white matter in ALS, but not in PDC patients. The concentrations of Zn are elevated for both patient groups, in both gray and white matter, but only the difference in gray matter for PDC is significant. For the other metals, no significant differences are found.

Aluminium as a risk factor in Alzheimer's disease, with emphasis on drinking water

Aluminium (Al) is clearly a powerful neurotoxicant. Considerable evidence exists that Al may play a role in the aetiology or pathogenesis of Alzheimer's disease (AD), but whether the link is causal is still open to debate. This paper reviews the epidemiological evidence linking Al and AD. Nine out of 13 published epidemiological studies of Al in drinking water and AD have shown statistically significant positive relations. Given the difficulty in producing high-quality data for the occurrence of AD and also for Al exposure, with the resulting unavoidable misclassification errors biasing any true association towards the null value, these studies are remarkably consistent. A major problem in their interpretation is that drinking water, even at high Al concentrations, only contributes a fraction of the total dietary intake of Al. In particular, regular consumers of antacids ingest gram amounts of Al daily, thousands of times the amounts taken in through drinking water, and epidemiological studies of antacid exposure and AD have been largely negative. However, Al is very poorly absorbed in the gastrointestinal tract, and the possibility that some Al fractions present in drinking water may be particularly bioavailable cannot be dismissed at present. The combined evidence linking Al and AD warrants substantial research efforts. Such efforts should focus on clarification of the cellular and molecular mechanisms in Al toxicity and of the basic metabolism and kinetics of Al in the human body, and on further epidemiological studies including diverse routes of Al exposure and also variables that are known or suspected to influence the individuals' susceptibility to AD, such as apolipoprotein E allele status and family history of AD.

Relations between nasopharyngeal carcinoma and magnesium and other alkaline earth elements in soils in China

Comparison of maps shows a striking geographical relation between high mortality rates from nasopharyngeal cancer in China and low contents of magnesium, calcium and strontium in the soil. We suggest that deficiencies of these elements in the soil could be indirect markers of aetiological factors, e.g. inhalable carcinogens of local natural origin. A search for such factors could be fruitful in further studies of environmental factors in the aetiology of nasopharyngeal carcinoma.

Prevention and treatment of aluminum toxicity including chelation therapy: status and research needs

The prevention and treatment of aluminum (Al) accumulation and toxicity are reviewed. Recommendations to further our understanding of desferrioxamine (deferoxamine, DFO) treatment and to develop more effective chelation approaches are provided. Reduction of Al accumulation and toxicity may benefit end-stage renal disease (ESRD) patients and perhaps those suffering from specific neurodegenerative disorders as well as workers with Al-induced neurocognitive disorders. The clearance of Al may be increased by extracorporeal chelation, renal transplantation, perhaps complexation with simple ligands such as silicon (Si), and systemic chelation therapy. The abilities of extracorporeal chelation and Si to reduce Al accumulation require further evaluation. Although it may not be possible to design Al-specific chelators, chelators with greater Al selectivity are desired. Aluminum-selective chelation might be achieved by targeted chelator distribution or by the use of adjuvants with the chelator. The ability of carboxylic acids to facilitate Al elimination, under specific conditions, warrants further study. Desferrioxamine does not produce significant biliary Al excretion. A chelator with this property may be useful in ESRD patients. The necessity for an Al chelator to distribute extravascularly to be effective is unknown and should be determined to guide the selection of alternatives to DFO. The lack of oral efficacy and occasional side effects of DFO encourage identification of orally effective, safer Al chelators. The bidentate 3-hydroxypyridin-4-ones are currently the most encouraging alternatives to DFO. They have been shown to increase urinary Al excretion in rats and rabbits, but to have toxicity comparable to, or greater than, DFO. Their toxicity may relate to incomplete metal complexation. The ability of orally effective chelators to increase absorption of chelated metal from the gastrointestinal (Gl) tract needs to be evaluated. Orally effective, safe Al chelators would be of benefit to peritoneal dialysis patients and those with neurodegenerative disorders, if Al chelation therapy is indicated. The reduction of Alzheimer's disease (AD) progression and the reversal of Al-induced behavioral deficits and neurofibrillary tangles by DFO encourage further study of Al chelation therapy for selected neurodegenerative disorders.

Speciation of aluminum in biological systems

As a "hard", trivalent metal ion, Al3- binds strongly to oxygen-donor ligands such as citrate and phosphate. The aqueous coordination chemistry of Al is complicated by the tendency of many Al complexes to hydrolyze and form polynuclear species, many of which are sparingly soluble. Thus there is considerable variation among the Al stability constants reported for several important ligands. The complexity in the aqueous chemistry of Al has also affected Al toxicity studies, which have often utilized poorly characterized Al stock solutions. Serum fractionation studies show that most Al is protein bound, primarily to the serum iron transport protein transferrin. Albumin appears to play little, if any, role in serum transport. There is little agreement as to the speciation of the remaining low-molecular mass fraction of serum Al. The lability of the Al3+ion precludes the simple separation and identification of individual Al complexes. Computational methods are available for detailed computer calculations of the Al speciation in serum, but efforts in this area have been severely hampered by the uncertainties regarding the stability constants of the low molecular mass Al complexes with citrate, phosphate, and hydroxide. Specific recommendations for further research on Al speciation include: (1) Determine more accurate Al stability constants with critical low molecular mass ligands such as citrate and phosphate; (2) supplement traditional potentiometric studies on Al complexes with data from other techniques such as 27Al-NMR and accelerator mass spectrometry with 26Al; (3) develop new methods for generating reliable linear free energy relationships for Al complexation; (4) determine equilibrium and rate constants for Al binding to transferrin at 37 degrees C; (5) confirm the possible formation of low-molecular-mass Al-protein complexes following desferrioxamine therapy; (6) continue research efforts to incorporate kinetic considerations into the present equilibrium speciation calculations; (7) improve methods for preparing chemically well-defined stock solutions for toxicological studies; (8) incorporate more detailed speciation data into studies on Al toxicity and pharmacokinetics; and (9) incorporate more detailed speciation data into future epidemiological studies on the relationship between Al toxicity and various water quality parameters.

Status and future concerns of clinical and environmental aluminum toxicology

A wide range of toxic effects of aluminum (Al) have been demonstrated in plants and aquatic animals in nature, in experimental animals by several routes of exposure, and under different clinical conditions in humans. Aluminum toxicity is a major problem in agriculture, affecting perhaps as much as 40% of arable soils in the world. In fresh waters acidified by acid rain, Al toxicity has led to fish extinction. Aluminum is a very potent neurotoxicant. In humans with chronic renal failure on dialysis, Al causes encephalopathy, osteomalacia, and anemia. There are also reports of such effects in certain patient groups without renal failure. Subtle neurocognitive and psychomotor effects and electroencephalograph (EEG) abnormalities have been reported at plasma Al levels as low as 50 micrograms/L. Infants could be particularly susceptible to Al accumulation and toxicity, reduced renal function being one contributory cause. Recent reports clearly show that Al accumulation occurs in the tissues of workers with long-term occupational exposure to Al dusts or fumes, and also indicate that such exposure may cause subtle neurological effects. Increased efforts should be directed toward defining the full range of potentially harmful effects in humans. To this end, multidisciplinary collaborative research efforts are encouraged, involving scientists from many different specialties. Emphasis should be placed on increasing our understanding of the chemistry of Al in biological systems, and on determining the cellular and molecular mechanisms of Al toxicity.

Chlorination of drinking water and cancer incidence in Norway

To examine whether chlorination of drinking water was associated with cancer of the digestive or other organs, an ecological epidemiological study using nationwide incidence data from the Cancer Registry of Norway was carried out. On two geographical levels (counties and municipalities), both for men and women, chlorination of drinking water was associated with an increased incidence of cancer of the colon and rectum. After adjusting for potential confounding variables, also measured on a geographical basis, the associations were still significant at the county level (adjusted for population density, income, education, fat and fibre intake etc.), but not at the municipality level. The observed associations are weak, chlorination being associated with a 20-40% increase in colorectal cancer rates. Due to inherent methodological limitations in ecological studies like the present one, causal interpretations should be made with great care. Thus, although the results give some support to the hypothesis that drinking water chlorination is associated with colorectal cancer, they do not provide strong evidence of a causal relationship.

Mortality from dementia among gastroduodenal ulcer patients

STUDY OBJECTIVE

The aim was to examine whether a high intake of aluminium containing antacids is a risk for Alzheimer's disease.

DESIGN

The mortality from dementia (1970-87), coded from death certificates as underlying or contributory cause of death, was compared with national rates in a cohort of patients who had surgery for gastroduodenal ulcer disease between 1911 and 1978.

SETTING

Patient data were obtained from patient records from major hospitals in western Norway.

PARTICIPANTS

4179 patients were identified who met the study criteria, which included having had a documented stomach operation, having a reliably identifiable personal number, and being alive on Jan 1, 1970.

MEASUREMENTS AND MAIN RESULTS

The standardised mortality ratio for dementia was 1.10 (95% CI 0.85-1.40, n = 64) for all patients, while for patients operated on in the period 1967-78 it was 1.25 (95% CI 0.66-2.13, n = 13).

CONCLUSIONS

As the majority of patients operated on after 1963 have probably been heavy consumers of aluminium containing antacids, the study provides meager evidence that a high intake of aluminium is an important risk factor for Alzheimer's disease, the major cause of dementia. However, the possibility of a raised mortality from Alzheimer's disease cannot be ruled out due to probable misclassification both in diagnosis and exposure. In addition, the observation period may have been too short to detect an effect since the latent period for Alzheimer's disease may be very long.

Geographical associations between aluminium in drinking water and death rates with dementia (including Alzheimer's disease), Parkinson's disease and amyotrophic lateral sclerosis in Norway

Comparisons of maps and correlation and regression analysis indicate a geographical association between aluminium (Al) in drinking water and registered death rates with dementia (coded from death certificates as the underlying or a contributory cause of death) in Norway. High levels of Al in drinking water are in most cases related to acid precipitation. In general, correlations between aggregate environmental measurements and mortality are a weak source of evidence for risk factors for disease, however, and interpretations regarding cause-and-effect relationships should therefore be made with great care. The major uncertainty probably relates to the use of registered death rates with dementia as a measure of incidence rates of Alzheimer's disease. The dementia rates are correlated with population density, and it is possible that the association between AI and dementia might be due to differences in diagnosis and reporting of dementia. Thus, the present study can only be regarded as introductory, and further epidemiological studies are needed to help elucidate the role of AI in Alzheimer's disease. The results provide little evidence of an association between AI in drinking water and Parkinson's disease or amyotrophic lateral sclerosis.

Mortality from dementia in Norway, 1969-83

From 1969 to the end of 1983 in Norway, dementia was coded as the underlying cause of death from 2058 death certificates, and as a contributory cause from 19,459. This is 3.56% of the total number of deaths. It seems that a considerable proportion of dementia cases are noted on death certificates in Norway. Death rates based on dementia as the underlying cause of death have increased with time, but when including contributory causes, rates have declined. The data may be useful in epidemiological studies, eg, to search for aetiological clues for Alzheimer's disease. Due to the inclusion of contributory causes of death in the registers and to the high number of dementia cases noted on death certificates, Norwegian mortality data on dementia are probably of better quality than in most other countries.