Whole-exome sequencing identifies novel protein-altering variants associated with serum apolipoprotein and lipid concentrations

BACKGROUND

Dyslipidemia is a major risk factor for cardiovascular disease, and diabetes impacts the lipid metabolism through multiple pathways. In addition to the standard lipid measurements, apolipoprotein concentrations provide added awareness of the burden of circulating lipoproteins. While common genetic variants modestly affect the serum lipid concentrations, rare genetic mutations can cause monogenic forms of hypercholesterolemia and other genetic disorders of lipid metabolism. We aimed to identify low-frequency protein-altering variants (PAVs) affecting lipoprotein and lipid traits.

METHODS

We analyzed whole-exome (WES) and whole-genome sequencing (WGS) data of 481 and 474 individuals with type 1 diabetes, respectively. The phenotypic data consisted of 79 serum lipid and apolipoprotein phenotypes obtained with clinical laboratory measurements and nuclear magnetic resonance spectroscopy.

RESULTS

The single-variant analysis identified an association between the LIPC p.Thr405Met (rs113298164) and serum apolipoprotein A1 concentrations (p=7.8×10^-8). The burden of PAVs was significantly associated with lipid phenotypes in LIPC, RBM47, TRMT5, GTF3C5, MARCHF10, and RYR3 (p<2.9×10^-6). The RBM47 gene is required for apolipoprotein B post-translational modifications, and in our data, the association between RBM47 and apolipoprotein C-III concentrations was due to a rare 21 base pair p.Ala496-Ala502 deletion; in replication, the burden of rare deleterious variants in RBM47 was associated with lower triglyceride concentrations in WES of >170,000 individuals from multiple ancestries (p=0.0013). Two PAVs in GTF3C5 were highly enriched in the Finnish population and associated with cardiovascular phenotypes in the general population. In the previously known APOB gene, we identified novel associations at two protein-truncating variants resulting in lower serum non-HDL cholesterol (p=4.8×10^-4), apolipoprotein B (p=5.6×10^-4), and LDL cholesterol (p=9.5×10^-4) concentrations.

CONCLUSIONS

We identified lipid and apolipoprotein-associated variants in the previously known LIPC and APOB genes, as well as PAVs in GTF3C5 associated with LDLC, and in RBM47 associated with apolipoprotein C-III concentrations, implicated as an independent CVD risk factor. Identification of rare loss-of-function variants has previously revealed genes that can be targeted to prevent CVD, such as the LDL cholesterol-lowering loss-of-function variants in the PCSK9 gene. Thus, this study suggests novel putative therapeutic targets for the prevention of CVD.

Association of Coding Variants in Hydroxysteroid 17-beta Dehydrogenase 14 (HSD17B14) with Reduced Progression to End Stage Kidney Disease in Type 1 Diabetes

BACKGROUND

Rare variants in gene coding regions likely have a greater impact on disease-related phenotypes than common variants through disruption of their encoded protein. We searched for rare variants associated with onset of ESKD in individuals with type 1 diabetes at advanced kidney disease stage.

METHODS

Gene-based exome array analyses of 15,449 genes in five large incidence cohorts of individuals with type 1 diabetes and proteinuria were analyzed for survival time to ESKD, testing the top gene in a sixth cohort (n=2372/1115 events all cohorts) and replicating in two retrospective case-control studies (n=1072 cases, 752 controls). Deep resequencing of the top associated gene in five cohorts confirmed the findings. We performed immunohistochemistry and gene expression experiments in human control and diseased cells, and in mouse ischemia reperfusion and aristolochic acid nephropathy models.

RESULTS

Protein coding variants in the hydroxysteroid 17-β dehydrogenase 14 gene (HSD17B14), predicted to affect protein structure, had a net protective effect against development of ESKD at exome-wide significance (n=4196; P value=3.3 × 10^-7). The HSD17B14 gene and encoded enzyme were robustly expressed in healthy human kidney, maximally in proximal tubular cells. Paradoxically, gene and protein expression were attenuated in human diabetic proximal tubules and in mouse kidney injury models. Expressed HSD17B14 gene and protein levels remained low without recovery after 21 days in a murine ischemic reperfusion injury model. Decreased gene expression was found in other CKD-associated renal pathologies.

CONCLUSIONS

HSD17B14 gene is mechanistically involved in diabetic kidney disease. The encoded sex steroid enzyme is a druggable target, potentially opening a new avenue for therapeutic development.

Differential metabolomic signatures of declining renal function in Types 1 and 2 diabetes

BACKGROUND

Chronic kidney disease (CKD) shows different clinical features in Types1 (T1D) and 2 diabetes (T2D). Metabolomics have recently provided useful contribution to the identification of biomarkers of CKD progression in either form of the disease. However, no studies have so far compared plasma metabolomics between T1D and T2D in order to identify differential signatures of progression of estimated glomerular filtration rate (eGFR) decline.

METHODS

We used two large cohorts of T1D (from Finland) and T2D (from Italy) patients followed up to 7 and 3 years, respectively. In both groups, progression was defined as the top quartile of yearly decline in eGFR. Pooled data from the two groups were analysed by univariate and bivariate random forest (RF), and confirmed by bivariate partial least squares (PLS) analysis, the response variables being type of diabetes and eGFR progression.

RESULTS

In progressors, yearly eGFR loss was significantly larger in T2D [-5.3 (3.0), median (interquartile range)mL/min/1.73 m2/year] than T1D [-3.7 (3.1) mL/min/1.73 m2/year ; P = 0.018]. Out of several hundreds, bivariate RF extracted 22 metabolites associated with diabetes type (all higher in T1D than T2D except for 5-methylthioadenosine, pyruvate and β-hydroxypyruvate) and 13 molecules associated with eGFR progression (all higher in progressors than non-progressors except for sphyngomyelin). Three of the selected metabolites (histidylphenylalanine, leucylphenylalanine, tryptophylasparagine) showed a significant interaction between disease type and progression. Only eight metabolites were common to both bivariate RF and PLS.

CONCLUSIONS

Identification of metabolomic signatures of CKD progression is partially dependent on the statistical model. Dual analysis identified molecules specifically associated with progressive renal impairment in both T1D and T2D.

Liver nucleotide biosynthesis is linked to protection from vascular complications in individuals with long-term type 1 diabetes

Identification of biomarkers associated with protection from developing diabetic complications is a prerequisite for an effective prevention and treatment. The aim of the present study was to identify clinical and plasma metabolite markers associated with freedom from vascular complications in people with very long duration of type 1 diabetes (T1D). Individuals with T1D, who despite having longer than 30 years of diabetes duration never developed major macro- or microvascular complications (non-progressors; NP) were compared with those who developed vascular complications within 25 years from diabetes onset (rapid progressors; RP) in the Scandinavian PROLONG (n = 385) and DIALONG (n = 71) cohorts. The DIALONG study also included 75 healthy controls. Plasma metabolites were measured using gas and/or liquid chromatography coupled to mass spectrometry. Lower hepatic fatty liver indices were significant common feature characterized NPs in both studies. Higher insulin sensitivity and residual ß-cell function (C-peptide) were also associated with NPs in PROLONG. Protection from diabetic complications was associated with lower levels of the glycolytic metabolite pyruvate and APOCIII in PROLONG, and with lower levels of thiamine monophosphate and erythritol, a cofactor and intermediate product in the pentose phosphate pathway as well as higher phenylalanine, glycine and serine in DIALONG. Furthermore, T1D individuals showed elevated levels of picolinic acid as compared to the healthy individuals. The present findings suggest a potential beneficial shunting of glycolytic substrates towards the pentose phosphate and one carbon metabolism pathways to promote nucleotide biosynthesis in the liver. These processes might be linked to higher insulin sensitivity and lower liver fat content, and might represent a mechanism for protection from vascular complications in individuals with long-term T1D.

Genome-Wide Association Study of Diabetic Kidney Disease Highlights Biology Involved in Glomerular Basement Membrane Collagen

BACKGROUND

Although diabetic kidney disease demonstrates both familial clustering and single nucleotide polymorphism heritability, the specific genetic factors influencing risk remain largely unknown.

METHODS

To identify genetic variants predisposing to diabetic kidney disease, we performed genome-wide association study (GWAS) analyses. Through collaboration with the Diabetes Nephropathy Collaborative Research Initiative, we assembled a large collection of type 1 diabetes cohorts with harmonized diabetic kidney disease phenotypes. We used a spectrum of ten diabetic kidney disease definitions based on albuminuria and renal function.

RESULTS

Our GWAS meta-analysis included association results for up to 19,406 individuals of European descent with type 1 diabetes. We identified 16 genome-wide significant risk loci. The variant with the strongest association (rs55703767) is a common missense mutation in the collagen type IV alpha 3 chain (COL4A3) gene, which encodes a major structural component of the glomerular basement membrane (GBM). Mutations in COL4A3 are implicated in heritable nephropathies, including the progressive inherited nephropathy Alport syndrome. The rs55703767 minor allele (Asp326Tyr) is protective against several definitions of diabetic kidney disease, including albuminuria and ESKD, and demonstrated a significant association with GBM width; protective allele carriers had thinner GBM before any signs of kidney disease, and its effect was dependent on glycemia. Three other loci are in or near genes with known or suggestive involvement in this condition (BMP7) or renal biology (COLEC11 and DDR1).

CONCLUSIONS

The 16 diabetic kidney disease-associated loci may provide novel insights into the pathogenesis of this condition and help identify potential biologic targets for prevention and treatment.

Metabolomic Profile Predicts Development of Microalbuminuria in Individuals with Type 1 Diabetes

Elevated urinary albumin excretion (microalbuminuria) is an early marker of diabetic nephropathy, but there is an unmet need for better biomarkers that capture the individuals at risk with higher accuracy and earlier than the current markers do. We performed an untargeted metabolomic study to assess baseline differences between individuals with type 1 diabetes who either developed microalbuminuria or remained normoalbuminuric. A total of 102 individuals progressed to microalbuminuria during a median follow-up of 3.2 years, whereas 98 sex-, age- and body mass index (BMI) matched non-progressors remained normoalbuminuric during a median follow-up of 7.1 years. Metabolomic screening identified 1,242 metabolites, out of which 111 differed significantly between progressors and non-progressors after adjustment for age of diabetes onset, baseline glycosylated hemoglobin A1c (HbA1c), and albumin excretion rate (AER). The metabolites that predicted development of microalbumiuria included several uremic toxins and carnitine metabolism related molecules. Iterative variable selection indicated erythritol, 3-phenylpropionate, and N-trimethyl-5-aminovalerate as the best set of variables to predict development of microalbuminuria. A metabolomic index based on these metabolites improved the prediction of incident microalbuminuria on top of the clinical variables age of diabetes onset, baseline HbA1c and AER (ROCAUC = 0.842 vs 0.797), highlighting their ability to predict early-phase diabetic nephropathy.

Confirmation of GLRA3 as a susceptibility locus for albuminuria in Finnish patients with type 1 diabetes

Urinary albumin excretion is an early sign of diabetic kidney disease, affecting every third individual with diabetes. Despite substantial estimated heritability, only variants in the GLRA3 gene have been genome-wide significantly associated (p-value < 5 × 10⁻⁸) with diabetic albuminuria, in Finnish individuals with type 1 diabetes; However, replication attempt in non-Finnish Europeans with type 1 diabetes showed nominally significant association in the opposite direction, suggesting a population-specific effect, but simultaneously leaving the finding controversial. In this study, the association between the common rs10011025 variant in the GLRA3 locus, and albuminuria, was confirmed in 1259 independent Finnish individuals with type 1 diabetes (p = 0.0013), and meta-analysis of all Finnish individuals yielded a genome-wide significant association. The association was particularly pronounced in subjects not reaching the treatment target for blood glucose levels (HbA_1c > 7%; N = 2560, p = 1.7 × 10⁻⁹). Even though further studies are needed to pinpoint the causal variants, dissecting the association at the GLRA3 locus may uncover novel molecular mechanisms for diabetic albuminuria irrespective of population background.

The Glanville fritillary genome retains an ancient karyotype and reveals selective chromosomal fusions in Lepidoptera

Previous studies have reported that chromosome synteny in Lepidoptera has been well conserved, yet the number of haploid chromosomes varies widely from 5 to 223. Here we report the genome (393 Mb) of the Glanville fritillary butterfly (Melitaea cinxia; Nymphalidae), a widely recognized model species in metapopulation biology and eco-evolutionary research, which has the putative ancestral karyotype of n=31. Using a phylogenetic analyses of Nymphalidae and of other Lepidoptera, combined with orthologue-level comparisons of chromosomes, we conclude that the ancestral lepidopteran karyotype has been n=31 for at least 140 My. We show that fusion chromosomes have retained the ancestral chromosome segments and very few rearrangements have occurred across the fusion sites. The same, shortest ancestral chromosomes have independently participated in fusion events in species with smaller karyotypes. The short chromosomes have higher rearrangement rate than long ones. These characteristics highlight distinctive features of the evolutionary dynamics of butterflies and moths.

Butterflies and moths (Lepidoptera) vary in chromosome number. Here, the authors sequence the genome of the Glanville fritillary butterfly, Melitaea cinxia, show it has the ancestral lepidopteran karyotype and provide insight into how chromosomal fusions have shaped karyotype evolution in butterflies and moths.

Alpha-tocopherol (vitamin E) and beta-carotene supplementation does not affect the risk for large abdominal aortic aneurysm in a controlled trial

Antioxidants may retard atherogenesis and limit inflammatory processes involved in aneurysm formation. We evaluated effects of alpha-tocopherol and beta-carotene supplementation on incidence of large abdominal aortic aneurysm (AAA) in a randomised, double-blind, placebo-controlled trial. Subjects (n=29133) were 50-69-years-old male smokers, participants in the Finnish alpha-Tocopherol, beta-Carotene Cancer Prevention (ATBC) Study. They were randomised to receive either 50 mg/day of alpha-tocopherol, or 20 mg/day of beta-carotene, or both, or placebo in a 2x2 design. Incidence of AAA was evaluated from mortality and hospital registers. During 5.8 years of follow-up, 181 men were diagnosed with either ruptured AAA (n=77) or nonruptured large AAA treated with aneurysmectomy (n=104). Relative risk (RR) for AAA was 0.83 (95% confidence interval [CI] 0.62-1.11) among men receiving alpha-tocopherol compared with those who did not, and 0.93 (95% CI 0.69-1.24) among men receiving beta-carotene compared with those who did not. A modest though nonsignificant decrease in risk for nonruptured AAA was observed among alpha-tocopherol supplemented men (RR 0.71, 95% CI 0.48-1.04) compared with men not receiving alpha-tocopherol. For beta-carotene, RR for nonruptured AAA was 0.86 (95% CI 0.59-1.27) compared with men not receiving beta-carotene. Neither antioxidant affected risk for ruptured AAA. In conclusion, long-term supplementation with alpha-tocopherol or beta-carotene had no preventive effect on large AAA among male smokers.

Season of birth among patients with schizophrenia and their siblings: evidence for the procreational habits hypothesis

OBJECTIVE

The birth rate of patients with schizophrenia during the winter and spring months is 5%-8% higher worldwide than the birth rate of the general population in the winter and spring months. Seasonal variation of births among the unaffected siblings of patients with schizophrenia has not been studied with adequate sample sizes. The authors investigated the seasonal variation of births among siblings of patients with schizophrenia in a large, nationwide, representative patient and sibling population.

METHOD

Finnish patients with schizophrenia born from 1950 to 1969 (N=15,389) were identified from three nationwide health care registers. Unaffected siblings of these patients born in the same time period (N=37,819) were identified from the Finnish National Population REGISTER: The seasonal variation of births among patients and siblings were examined by using a log-linear model. Explanatory variables were sex, year of birth categorized into four 5-year groups, and seasonal variation, which was analyzed by fitting a short Fourier series to the monthly birth data.

RESULTS

The odds for having been born during the winter-spring months were slightly higher among both siblings and patients in all birth-year groups. However, patients born from 1955 to 1959 showed prominent seasonal variation of births, but the magnitude of this variation remained unchanged among siblings.

CONCLUSIONS

Seasonal variation of births among patients with schizophrenia may consist of two factors: 1) parental procreational habits causing a slight excess of births of both patients and unaffected siblings during the winter-spring months and 2) irregular environmental factors that considerably increase the magnitude of the seasonal variation of births among patients but not their siblings.

Life-style factors and risk for abdominal aortic aneurysm in a cohort of Finnish male smokers

Prospective studies evaluating risk factors for abdominal aortic aneurysm are few. We studied the association of life-style factors with risk for abdominal aortic aneurysm among 29,133 male smokers 50-69 years of age, participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. During a mean follow-up of 5.8 years, 181 were diagnosed with ruptured abdominal aortic aneurysm or nonruptured abdominal aortic aneurysm plus aneurysmectomy. Risk for abdominal aortic aneurysm was positively associated with age [relative risk (RR) = 4.56, 95% confidence interval (CI) = 2.42-8.61 for > 65 vs < or = 55 years], smoking years (RR = 2.25, 95% CI = 1.33-3.81 for > 40 vs < or = 32 years), systolic blood pressure (RR = 1.92, 95% CI = 1.13-3.25 for > 160 vs < or = 130 mmHg), diastolic blood pressure (RR = 1.80, 95% CI = 1.05-3.08 for > 100 vs < or = 85 mmHg), and serum total cholesterol (RR = 1.85, 95% CI = 1.09-3.12 for > 6.5 vs < or = 5.0 mmol/liter). High-density lipoprotein cholesterol showed a strong inverse association with risk for aortic aneurysm (RR = 0.16, 95% CI = 0.08-0.32 for > 1.5 vs < or = 0.9 mmol/liter). High energy intake was associated with lower risk for aortic aneurysm (RR = 0.59, 95% CI = 0.38-0.94 for the highest quartile vs the lowest), whereas no associations with nutrients were evident. We conclude that classical risk factors for atherosclerotic diseases seem to be important in pathogenesis of large abdominal aortic aneurysms.

Prospective study of diet, lifestyle, and intermittent claudication in male smokers

The association between dietary and lifestyle factors and intermittent claudication was investigated in the Finnish Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. The cohort comprised 26,872 male smokers aged 50-69 years who were free of claudication at study entry. At baseline (1985-1988), subjects completed a diet history questionnaire. During a median follow-up period of 4 years (ending in spring 1993), 2,578 men reported symptoms of claudication on the Rose questionnaire, which was administered annually. Smoking status was assessed every 4 months. Smoking, systolic blood pressure, serum total cholesterol, and diabetes mellitus were positively associated with risk for claudication, whereas serum high density lipoprotein cholesterol, education, and leisure time exercise were inversely associated with risk. Dietary carbohydrates, fiber, and n-6 polyunsaturated fatty acids were inversely associated with risk for claudication, as were some dietary and serum antioxidants: dietary vitamin C (highest quartile vs. lowest: relative risk (RR) = 0.86; 95% confidence interval (CI): 0.77, 0.97), dietary gamma-tocopherol (RR = 0.89; 95% CI: 0.79, 1.00), dietary carotenoids (RR = 0.82; 95% CI: 0.73, 0.92), serum alpha-tocopherol (RR = 0.88; 95% CI: 0.77, 1.00), and serum beta-carotene (RR = 0.77; 95% CI: 0.68, 0.86). Smoking cessation reduced subsequent risk for claudication (RR = 0.86; 95% CI: 0.75, 0.99). The authors conclude that classical risk factors for atherosclerosis are associated with claudication. High intakes of antioxidant vitamins may be protective. Further research is needed before antioxidants can be recommended for the prevention of intermittent claudication.

Decreasing seasonal variation of births in schizophrenia

BACKGROUND

Patients with schizophrenia have a winter-spring excess of births compared with the general population, the cause of which is unresolved. Fluctuations in the magnitude of the seasonal variation may provide clues to its aetiology.

METHODS

All Finnish patients with schizophrenia born between 1950 and 1969 (N = 15892) were identified from two nationwide health-care registers. Their background demographic information was obtained from the Population Register Centre, which also provided monthly numbers of births in each municipality of Finland as multidimensional tables, with sex and year, month and place of birth as marginals. The incidence of schizophrenia was modelled using Poisson regression analysis, with sex, onset age, birth cohort, place of birth (urban/rural), trend and seasonal variation as explanatory variables. We also constructed a monthly time series and decomposed it into three components--seasonal, trend and remainder.

RESULTS

Seasonal variation of births among patients born in the 1950s, especially between 1955 and 1959, was marked, but decreased among patients born in the 1960s. No interaction between place of birth or sex and seasonal variation was observed. The incidence was higher among the rural-born than the urban-born, but declined more slowly among the urban-born than the rural-born.

CONCLUSIONS

The intensity of the factor causing the seasonal variation of births in schizophrenia may be decreasing. Urban birth may be emerging as a risk factor for schizophrenia in Finland, as elsewhere.

The effect of alpha-tocopherol and beta-carotene supplementation on symptoms and progression of intermittent claudication in a controlled trial

We evaluated the effect of long-term supplementation with vitamin E (alpha-tocopherol) and beta-carotene on occurrence of claudication symptoms and risk for peripheral vascular surgery among men with intermittent claudication. Subjects, 50-69-year old male smokers, were participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, who reported intermittent claudication through a structured questionnaire (Rose) at study entry (n=1484). They were randomly assigned to receive either 50 mg/day of alpha-tocopherol, or 20 mg/day of beta-carotene, or both, or placebo, in a 2 x 2 design. During follow-up, claudication was evaluated by repeating use of the questionnaire once a year. Information on peripheral vascular surgery came from the National Hospital Discharge Register. We observed no effect of alpha-tocopherol and beta-carotene supplementation on claudication during a mean follow-up of 3.7 years. A slightly increased risk (odds ratio (OR) 1.60, 95% confidence interval (CI) 1.05-2.44) for vascular surgery was observed among beta-carotene supplemented men compared to those who did not receive beta-carotene. Alpha-tocopherol supplementation had no effect. In conclusion, long-term supplementation with alpha-tocopherol and beta-carotene showed no beneficial effect on symptoms and progression of intermittent claudication.

The association between smoking cessation and periodontal status and salivary proteinase levels

BACKGROUND

Little information is available about the effects of the cessation of cigarette smoking on oral health, although cigarette smoking has been shown to be associated with a variety of oral diseases. The aim of this study was to compare periodontal status, salivary proteolytic activity, especially collagenase-2 (MMP-8) levels, and oral mucosal status in individuals who had quit smoking for at least 6 months (mean 3.5, SD 1.3 years) and in regular smokers.

METHODS

The subjects were 409 white male smokers aged 55 to 74 years with 15 or more remaining teeth. They had participated in a major cancer prevention study (ATBC Study). Eighty-two of the men had given up smoking and 327 were smokers. The subjects were examined clinically to determine the prevalence of periodontal pockets, gingival bleeding (BOP) and suppuration, and prevalence of keratotic oral mucosal lesions. The loss of alveolar bone was determined radiographically. Candida albicans was cultivated, and lesions showing leukoplakia were examined histopathologically. General proteolytic activity and collagenase-2 or matrix metalloproteinase-8 (MMP-8) levels in saliva, salivary pH, and buffering capacity were measured. Linear regression, logistic regression, or Fisher's exact test were used in statistical analysis.

RESULTS

Salivary general proteolytic activity and MMP-8 levels were lower in current smokers than in ex-smokers (P <0.05 and P <0.05, respectively). The prevalence of > or = 4 mm deep pockets, gingival suppuration, and loss of crestal bone were statistically significantly lower (P = 0.003, P<0.001, and P<0.05, respectively) and salivary buffering capacity higher (P <0.05) in those who had quit smoking compared to current smokers; there was no difference in BOP. The prevalence of oral leukoplakia did not differ significantly between smokers and quitters, but was higher in those who smoked >15 cigarettes per day compared to quitters (odds ratio 3.5, 95% CI, 0.8 to 15.3).

CONCLUSIONS

These data suggest that periodontal status and oral mucosal health are better in those who have quit cigarette smoking compared to current smokers. However, the data further suggest that smoking may significantly lower both general proteolytic enzyme activity and MMP-8 levels in saliva. Thus, care should be taken in interpreting results revealing salivary/mouthrinse proteinases as diagnostic markers for oral/periodontal disease activity.

Decline in the incidence of schizophrenia in Finnish cohorts born from 1954 to 1965

BACKGROUND

The declining incidence of schizophrenia observed in several countries is believed by many to merely reflect methodological problems in the studies performed. We report the first nationwide historical cohort study of changes in the incidence of schizophrenia, in which many of the previous methodological problems were overcome.

METHODS

We used the Finnish Population Register to identify everyone born in Finland from 1954 to 1965. These persons were followed up from their 16th to their 26th birthdays, and all cases of schizophrenia (International Classification of Diseases, Eighth Revision and International Classification of Diseases, Ninth Revision code 295) that emerged were identified from the National Hospital Discharge Register, the Pension Register, and the Free Medicine Register. Persons for whom an age of onset could be defined were included in the analyses (n = 5645). We used the Poisson regression model to estimate the effects of age, sex, birth cohort, period of diagnosis, and season of birth on the incidence of schizophrenia. The relative importance of cohort and period were assessed using an age-period-cohort model.

RESULTS

The incidence declined significantly in each successive cohort, from 0.79 to 0.53 per 1000 among males and from 0.58 to 0.41 per 1000 among females. The effects of cohort and period on the change were both significant.

CONCLUSIONS

The incidence of schizophrenia has declined in Finland. This was partly caused by confounding factors, as reflected in the significant period effect. The significant birth cohort effect suggests that the intensity or frequency of one or more risk factors for schizophrenia has decreased.

The effects of supplementation with alpha-tocopherol and beta-carotene on the incidence and mortality of carcinoma of the pancreas in a randomized, controlled trial

BACKGROUND

Dietary components may be both causal and protective in cases of pancreatic carcinoma, but the preventive potential of single constituents has not been evaluated. The authors report the effects of alpha-tocopherol and beta-carotene supplementations on the rates of incidence of and mortality from pancreatic carcinoma in a randomized, controlled trial.

METHODS

The 29,133 participants in the Alpha-Tocopherol Beta-Carotene Cancer Prevention (ATBC) Study were male smokers who were ages 50-69 years at the time they were randomized into 1 of the following 4 intervention groups: dl-alpha-tocopherol (AT; 50 mg/day), beta-carotene (BC; 20 mg/day), both AT and BC, and placebo. The daily supplementation lasted for 5-8 years. Incident cancers were identified through the national Finnish Cancer Registry and death certificates of the Statistics Finland. Results were analyzed by supplementation with Cox regression models.

RESULTS

Effects of both supplementations were statistically nonsignificant. The rate of incidence of pancreatic carcinoma was 25% lower for the men who received beta-carotene supplements (n = 38) compared with the rate for those who did not receive beta-carotene (n = 51) (95% CI, -51% to 14%). Supplementation with alpha-tocopherol (n = 51) increased the rate of incidence by 34% (95% CI, -12% to 105%) compared with the rate for those who did not receive alpha-tocopherol. Mortality from pancreatic carcinoma during the follow-up, adjusted for stage and anatomic location of the tumor, was 19% (95% CI, -47% to 26%) lower among those who received beta-carotene and 11% (95% CI, -28% to 72%) higher among those who received alpha-tocopherol as compared with those who did not receive supplementation.

CONCLUSIONS

Supplementation with beta-carotene or alpha-tocopherol does not have a statistically significant effect on the rate of incidence of pancreatic carcinoma or the rate of mortality caused by this disease.

Beta-carotene concentration in buccal mucosal cells with and without dysplastic oral leukoplakia after long-term beta-carotene supplementation in male smokers

OBJECTIVE

To measure the beta-carotene concentration in buccal mucosal cells in smoking men who had received long-term beta-carotene (BC) supplementation in a controlled trial. To assess the association of cellular BC on the prevalence of dysplasia in oral leukoplakia.

DESIGN

An end-of-trial examination of a part of subjects in the Alpha-Tocopherol, Beta Carotene Cancer Prevention Study.

SUBJECTS AND METHODS

343 men who for 5-7 years had received BC (20 mg/d) or alpha-tocopherol (AT) (50 mg/d), or both of these or placebo. BC concentration of buccal mucosal cells was compared in the subjects with BC supplementation (n = 173) to that of those without it (n = 170). Oral mucosae were examined clinically and lesions showing leukoplakia histopathologically.

RESULTS

Mean (s.d.) BC concentration in buccal mucosal cells was 7.7 (10.3)mg/kg protein in the subjects who received BC compared to 1.1 (1.7) mg/kg protein in those who did not. The BC concentration in the cells of supplemented subjects correlated with their serum BC levels (P < 0.001). AT supplementation had no effect on BC concentration nor was daily amount of smoking statistically significantly associated with the BC concentration in buccal cells. Altogether 17 subjects showed oral leukoplakia, 7 had dysplasia. In these 7 subjects, the BC concentration in buccal mucosal cells did not differ statistically significantly compared to subjects with only hyperkeratosis (n = 10) (F-test, P = 0.74).

CONCLUSIONS

After long-term BC supplementation, BC concentration in oral mucosal cells was 7-fold greater than without supplementation. There was no evidence to support an association between cellular BC concentration and precancerous lesions among the few subjects having them in their oral mucosae.

Increased tendency towards gingival bleeding caused by joint effect of alpha-tocopherol supplementation and acetylsalicylic acid

Alpha-tocopherol (vitamin E) may play a role in the treatment of arterial thromboembolic disease, possibly by inhibiting platelet aggregation. Thus far, no clinical evidence exists for this effect. The objective of this study was to assess the effect of alpha-tocopherol supplementation on gingival bleeding either in combination with acetylsalicylic acid (ASA) or without it. This study was an end-point examination of a random sample of male smokers who had participated in a controlled clinical trial, the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC Study) for 5-7 years. The study included 409 men aged 55-74 years of whom 191 received alpha-tocopherol supplementation (50 mg/day); 56 used ASA, 30 received both and 132 received neither. Gingival bleeding was examined by probing with a WHO probe and reported as a percentage of bleeding sites adjusted by the logistic regression model. Gingival bleeding was more common in those who received alpha-tocopherol compared with nonreceivers among subjects with a high prevalence of dental plaque (P < 0.05). ASA alone increased bleeding only slightly. The highest risk of gingival bleeding was among those who took both alpha-tocopherol and ASA (33.4% of probed sites bleeding vs 25.8% among subjects taking neither alpha-tocopherol nor ASA, P < 0.001). In the ATBC Study, more deaths from haemorrhagic stroke and fewer from ischaemic heart disease were observed among those participants who received alpha-tocopherol compared with those who did not. Based on the results of the present study and the ATBC Study, we conclude that alpha-tocopherol supplementation may increase the risk of clinically important bleedings, particularly when combined with ASA.

Effects of alpha tocopherol and beta carotene supplements on symptoms, progression, and prognosis of angina pectoris

OBJECTIVE

To evaluate the effects of alpha tocopherol and beta carotene supplements on recurrence and progression of angina symptoms, and incidence of major coronary events in men with angina pectoris.

DESIGN

Placebo controlled clinical trial.

SETTING

The Finnish alpha tocopherol beta carotene cancer prevention study primarily undertaken to examine the effects of alpha tocopherol and beta carotene on cancer.

SUBJECTS

Male smokers aged 50-69 years who had angina pectoris in the Rose chest pain questionnaire at baseline (n = 1795).

INTERVENTIONS

alpha tocopherol (vitamin E) 50 mg/day, beta carotene 20 mg/day or both, or placebo in 2 x 2 factorial design.

MAIN OUTCOME MEASURES

Recurrence of angina pectoris at annual follow up visits when the questionnaire was readministered; progression from mild to severe angina; incidence of major coronary events (non-fatal myocardial infarction and fatal coronary heart disease).

RESULTS

There were 2513 recurrences of angina pectoris during follow up (median 4 years). Compared to placebo, the odds ratios for recurrence in the active treatment groups were: alpha tocopherol only 1.06 (95% confidence interval (CI) 0.85 to 1.33), alpha tocopherol and beta carotene 1.02 (0.82 to 1.27), beta carotene only 1.06 (0.84 to 1.33). There were no significant differences in progression to severe angina among the groups given supplements or placebo. Altogether 314 major coronary events were observed during follow up (median 5.5 years) and the risk for them did not differ significantly among the groups given supplements or placebo.

CONCLUSIONS

There was no evidence of beneficial effects for alpha tocopherol or beta carotene supplements in male smokers with angina pectoris, indicating no basis for therapeutic or preventive use of these agents in such patients.

Effect of alpha-tocopherol (vitamin E) and beta-carotene supplementation on the incidence of intermittent claudication in male smokers

We examined the primary preventive effect of vitamin E (alpha-tocopherol) and beta-carotene supplementation on intermittent claudication. The subjects--participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study--were male smokers aged 50 to 69 years who were randomly assigned to receive 50 mg of alpha-tocopherol daily, 20 mg of beta-carotene daily, both, or placebo. At baseline, there were 26 289 men with no history or symptoms of intermittent claudication. The Rose questionnaire on intermittent claudication was administered annually to discover incident cases. We observed 2704 cases of first occurrence of typical intermittent claudication during a median follow-up time of 4.0 years. Compared with placebo, the adjusted relative risk for typical intermittent claudication among those who received alpha-tocopherol only was 1.11 (95% confidence interval, 1.00-1.24); among those who received alpha-tocopherol and beta-carotene, 1.02 (0.91-1.13); and among those who received beta-carotene only, 1.02 (0.92-1.14). When we compared the alpha-tocopherol-supplemented subjects with those who received no alpha-tocopherol, the adjusted relative risk for typical intermittent claudication was 1.05 (0.98-1.14), and for beta-carotene-supplemented subjects compared with those who did not receive beta-carotene, the relative risk was 0.96 (0.89-1.04). In conclusion, no primary preventive effect on intermittent claudication was observed among middle-aged male smokers who were supplemented with alpha-tocopherol, beta-carotene, or both.

Effect of vitamin E and beta carotene on the incidence of angina pectoris. A randomized, double-blind, controlled trial

OBJECTIVE

To examine the effect of supplementation with vitamin E (alpha tocopherol), beta carotene, or both on the incidence of angina pectoris in men without known previous coronary heart disease.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING AND PARTICIPANTS

Participants in the Alpha Tocopherol, Beta Carotene Cancer Prevention Study (N=29133) were male smokers aged 50 through 69 years who were living in southern and western Finland. Of these men, 22269 were considered free of coronary heart disease at baseline and were followed up for the incidence of angina pectoris.

INTERVENTION

Participants were randomized to receive 50 mg/d of alpha tocopherol, 20 mg/d of beta carotene, both, or placebo in a 2x2 design.

OUTCOME MEASURES

An incident case was defined as the first occurrence of typical angina pectoris identified in administering the annually repeated World Health Organization (Rose) Chest Pain Questionnaire.

RESULTS

During a median follow-up time of 4.7 years (96427 person-years), 1983 new cases of angina pectoris were detected. Comparing alpha tocopherol-supplemented subjects with non-alpha tocopherol-supplemented subjects showed a relative risk (RR) of angina pectoris incidence of 0.91 (95% confidence interval[CI], 0.83 to 0.99; P=.04). The RR for incidence of angina pectoris for the beta carotene- supplemented subjects compared with those not receiving beta carotene was 1.06 (95% CI, 0.97 to 1.16; P=.19). Compared with those receiving placebo, the RRs for incidence of angina pectoris were 0.97 (95% CI, 0.85 to 1.10) and 0.96 (95% CI, 0.85 to 1.09) in the alpha tocopherol and alpha tocopherol plus beta carotene groups, respectively, and 1.13 (95% CI, 1.00 to 1.27) in the beta carotene group (P=.06). Baseline dietary intakes and serum levels of alpha tocopherol and beta carotene did not predict incidence of angina pectoris.

CONCLUSIONS

Supplementation with alpha tocopherol was associated with only a minor decrease in the incidence of angina pectoris. Beta carotene had no preventive effect and was associated with a slight increase of angina.

Correction for covariate measurement error in generalized linear models--a bootstrap approach

A two-phase bootstrap method is proposed for correcting covariate measurement error. Two data sets are needed: validation data for approximating the measurement model and data with a response variable. Bootstrap samples from both the data sets validation data are taken. Parameter estimates of the generalized linear model are calculated using expectations of the measurement model from the validation data as explanatory variables. The method is compared through simulation in logistic regression with the correction method proposed by Rosner, Willet, and Spiegelman (1991, Statistics in Medicine 8, 1051-1069). A real data example is also presented.