Longitudinal Population-based Studies Research Articles

Modifiable lifestyle factors in dementia: a systematic review of longitudinal observational cohort studies.

Numerous population-based longitudinal studies suggest an association between modifiable lifestyle factors and late-life dementia. A comprehensive description of these factors and their quantification criteria is an important preliminary step toward the elucidation of causes and mechanisms underlying the onset and progression of dementia. To present a systematic review of modifiable lifestyle factors associated with dementia risk in longitudinal observational cohort-studies. A systematic review of original articles, published in English until December 2013, listed in four electronic databases (including PubMed, MEDLINE, PsycINFO) was conducted. 75 papers from 33 epidemiologic studies met the inclusion criteria. Included papers focused on dietary habits (n = 26), leisure activities (social, physical, mental) (n = 23), beverages (juice, tea, coffee, alcohol) (n = 15), smoking (n = 13), social network (n = 6), and combined lifestyle factors (n = 2). Broad consensus emerged on the protective role against dementia of leisure activities. Conflicting results were found for the association between dementia and putative risk factors (smoking) and protective factors (mild-to-moderate alcohol consumption, dietary antioxidants, Mediterranean diet, and living with others). However, studies varied largely in the quantification of lifestyle factors in terms of intensity, frequency and duration of exposure, and in the choice of confounders in statistical analyses. The need for standardized quantification criteria emerges, together with the current limitation in reliably tracking the past history of each patient, from childhood and young adulthood to midlife.

Lipopolysaccharide binding protein, obesity status and incidence of metabolic syndrome: a prospective study among middle-aged and older Chinese.

Although microbiota-derived endotoxaemia has previously been shown to induce metabolic disorders, data from population-based longitudinal studies are scarce. This study therefore investigated the associations between lipopolysaccharide binding protein (LBP) levels and 6 year incident metabolic syndrome (MetS), as well as the potentially modifying effects of obesity status in middle-aged and older Chinese men and women. A total of 2,529 men and women aged 50-70 years from Beijing and Shanghai, China, were followed for 6 years. Those free of MetS at baseline (1,312) were included in the analyses for the risk of developing MetS. Baseline plasma LBP was measured using an ELISA kit. During the 6 year follow-up, 449 (34.2%) participants developed MetS. Baseline LBP was significantly associated with BMI, waist circumference, blood lipid profile and C-reactive protein (CRP) both at baseline and during follow-up (all p < 0.05). The RR for incident MetS comparing extreme quartiles of LBP was 1.28 (95% CI 1.04, 1.58), after multivariate adjustment including BMI and CRP. In stratified analysis, LBP was positively associated with incident MetS only in normal-weight participants (RR, comparing extreme tertiles, 1.59; 95% CI 1.18, 2.15; p(trend)= 0.002), but not in their overweight/obese counterparts (RR, comparing extreme tertiles, 0.99; 95% CI 0.80, 1.22; p(trend) = 0.880). A significant interaction was observed between LBP and obesity status (p(interaction) = 0.013). Our study suggested that elevated plasma LBP was associated with an increased risk of developing MetS among middle-aged and older Chinese, especially in normal-weight individuals.

Impact of Metabolic Syndrome on Cognitive Decline in Older Age: Protective or Harmful, Where is the Pitfall?

Metabolic syndrome (MetS) has been found to be a risk factor for dementia, mild cognitive impairment, and its associated states. However, a definitive conclusion cannot be drawn from the available data. Discrepancies between the results are due to several factors, e.g., study design, heterogeneity of the population enrolled, reliability and sensitivity of detection tools for cognitive changes, cut-offs and criteria used to diagnose MetS, the outcome measures considered, MetS duration before the onset of cognitive decline, and also the analytical approach performed. Recently, a systematic review and meta-analysis including 19,522 subjects aged 59-85 years from 13 longitudinal population-based studies has been conducted to examine the association between MetS and longitudinal changes in cognitive functions. While a marginal significant association was found in the younger old group, this relationship was not observed in older group (>70 years). It is not yet clear how age can influence this relationship. Apart from methodological issues, other biological factors are likely involved in this direction reversal.

594 Incidence and remission of nocturia: A systematic review of longitudinal population-based studies with meta-analysis and meta-regression

594 Incidence and remission of nocturia: A systematic review of longitudinal population-based studies with meta-analysis and meta-regression

Epidemiological studies of CHD and the evolution of preventive cardiology

Cardiovascular diseases (CVDs) cause nearly one-third of all deaths worldwide. Coronary heart disease (CHD) accounts for the greatest proportion of CVDs, and risk factors such as hypertension, cigarette smoking, diabetes mellitus or elevated glucose level, elevated cholesterol levels, and obesity or being overweight are the top six causes of death globally. Ecological and population-based longitudinal studies, conducted globally or within individual countries, have established the role of traditional and novel risk factors and measures of subclinical disease in the prediction of CHD. Risk assessment with short-term or long-term risk prediction algorithms can help to identify individuals who would benefit most from risk-factor interventions. Evaluation of novel risk factors and screening for subclinical atherosclerosis can also help to identify individuals at highest cardiovascular risk. Prevention of CHD focuses on identifying and managing risk factors at both the population and individual levels through primordial, primary, and secondary prevention. Epidemiological studies have provided the hypotheses for subsequent clinical trials that have documented the efficacy of risk-factor interventions, which are the basis of preventive cardiology. Future research efforts will determine the screening and intervention strategies that have the greatest effect on CHD prevention.

Dementia studies in Chinese populations

Variations in the prevalence of dementia in different ethnic groups have been reported worldwide, and a number of reviews have provided a picture of epidemiological studies in dementia research. However, little is known about epidemiological studies in Chinese populations. In this review, we searched PubMed and the Web of Science for original research articles published in English up to July 2013 on the prevalence, incidence, risk factors, and prognosis of dementia in Chinese populations worldwide. Except for the prevalence, we included only population-based follow-up studies. We identified 25 studies in elderly Chinese residents in Mainland China, Hong Kong, Taiwan, and Singapore, and found a higher prevalence of dementia in Mainland China than in the other locations, which may be due to that the studies from Mainland China are more recent than those from other locations. A notable increase in incidence was observed when dementia cases were diagnosed using 10/66 diagnostic criteria compared to other criteria. Studies on risk factors for dementia were limited and mostly from Mainland China. Age, gender, education, smoking, and alcohol consumption were related to the risk of dementia in Chinese populations. Only two prognostic studies were identified, and age, gender, and residential area were related to the prognosis of dementia. In conclusion, the prevalence, incidence, and risk factors for dementia found in Chinese populations were comparable to other ethnic groups, but no conclusive results on prognosis were found. The differences in prevalence and incidence were influenced by the diagnostic criteria and the time of study. Longitudinal population-based studies on the incidence, risk factors, and prognosis of dementia in Chinese populations are required.

Mild cognitive impairment: a concept in evolution

The construct of mild cognitive impairment (MCI) has evolved over the past 10 years since the publication of the new MCI definition at the Key Symposium in 2003, but the core criteria have remained unchanged. The construct has been extensively used worldwide, both in clinical and in research settings, to define the grey area between intact cognitive functioning and clinical dementia. A rich set of data regarding occurrence, risk factors and progression of MCI has been generated. Discrepancies between studies can be mostly explained by differences in the operationalization of the criteria, differences in the setting where the criteria have been applied, selection of subjects and length of follow-up in longitudinal studies. Major controversial issues that remain to be further explored are algorithmic versus clinical classification, reliability of clinical judgment, temporal changes in cognitive performances and predictivity of putative biomarkers. Some suggestions to further develop the MCI construct include the tailoring of the clinical criteria to specific populations and to specific contexts. The addition of biomarkers to the clinical phenotypes is promising but requires deeper investigation. Translation of findings from the specialty clinic to the population setting, although challenging, will enhance uniformity of outcomes. More longitudinal population-based studies on cognitive ageing and MCI need to be performed to clarify all these issues.

Comparison of alternate scoring of variables on the performance of the frailty index

BackgroundThe frailty index (FI) is used to measure the health status of ageing individuals. An FI is constructed as the proportion of deficits present in an individual out of the total number of age-related health variables considered. The purpose of this study was to systematically assess whether dichotomizing deficits included in an FI affects the information value of the whole index.MethodsSecondary analysis of three population-based longitudinal studies of community dwelling individuals: Nova Scotia Health Survey (NSHS, n = 3227 aged 18+), Survey of Health, Ageing and Retirement in Europe (SHARE, n = 37546 aged 50+), and Yale Precipitating Events Project (Yale-PEP, n = 754 aged 70+). For each dataset, we constructed two FIs from baseline data using the deficit accumulation approach. In each dataset, both FIs included the same variables (23 in NSHS, 70 in SHARE, 33 in Yale-PEP). One FI was constructed with only dichotomous values (marking presence or absence of a deficit); in the other FI, as many variables as possible were coded as ordinal (graded severity of a deficit). Participants in each study were followed for different durations (NSHS: 10 years, SHARE: 5 years, Yale PEP: 12 years).ResultsWithin each dataset, the difference in mean scores between the ordinal and dichotomous-only FIs ranged from 0 to 1.5 deficits. Their ability to predict mortality was identical; their absolute difference in area under the ROC curve ranged from 0.00 to 0.02, and their absolute difference between Cox Hazard Ratios ranged from 0.001 to 0.009.ConclusionsAnalyses from three diverse datasets suggest that variables included in an FI can be coded either as dichotomous or ordinal, with negligible impact on the performance of the index in predicting mortality.

The potential to predict the course of childhood asthma

Many children experience pre-school or early childhood wheezing. In a significant proportion symptoms disappear as the child grows, but others have persistent and troublesome asthma which can be life-long. Tools to predict course of disease in young children are a priority for families and clinicians. This review summarizes evidence from several longitudinal population-based birth-cohort studies that have identified risk factors for persistence and remission of childhood asthma. These factors include clinical characteristics, environmental and other exposures, familial factors, biomarkers of allergic inflammation, measurements of lung function and airway responsiveness, and genetic variants. This review also introduces the concept of polygenic risk and genetic risk scores, and describes results from a recent study that suggests promise for the use of genetic information in predicting the course of childhood asthma. We conclude with a discussion of implications and future directions.

A Population-Based Cohort Study on Chronic Obstructive Pulmonary Disease in Latin America: Methods and Preliminary Results. The PLATINO Study Phase II

BackgroundThe PLATINO baseline study, conducted from 2003 to 2005 in five Latin American cities (São Paulo, Mexico City, Montevideo, Santiago, Caracas), showed a high prevalence of chronic obstructive pulmonary disease (COPD). Methods/designA follow-up study was conducted in three out of the five centers (Montevideo, Santiago, and São Paulo) after a period of 5, 6 and 9years, respectively, aimed at verifying the stability of the COPD diagnosis over time, the evolution of the disease in terms of survival, morbidity and respiratory function, and the analyses of inflammatory and genetic biomarkers in the blood. Some questions were added to the original questionnaire and death certificates were obtained from the national official registries. ResultsThe fieldwork has been concluded in the three centers. From the original samples in the PLATINO study phase i, we were able to locate and interview 85.6% of patients in Montevideo, 84.7% in Santiago and 77.7% in São Paulo. Individuals who could not be located had higher education levels in Brazil, and were more likely to be current smokers in Santiago and São Paulo than in Montevideo. The overall quality of spirometries was ≥80% according to American Thoracic Society criteria. The number of deaths was 71 (Montevideo), 95 (Santiago) and 135 (São Paulo), with death certificates obtained from the national mortality registries for 76.1%, 88.3% and 91.8% of cases in Montevideo, Santiago and São Paulo, respectively. ConclusionsThis study shows that it is possible to perform population-based longitudinal studies in Latin American with high follow-up rates and high-quality spirometry data. The adequacy of national mortality registries varies among centers in Latin America.

Estudio de cohorte de base poblacional sobre la enfermedad pulmonar obstructiva crónica en Latinoamérica: métodos y resultados preliminares. Fase II del estudio PLATINO

BackgroundThe PLATINO baseline study, conducted from 2003-2005 in five Latin American cities (São Paulo, Mexico City, Montevideo, Santiago, Caracas), showed a high prevalence of chronic obstructive pulmonary disease (COPD). Methods/designA follow-up study was conducted in three out of the five centers (Montevideo, Santiago, and São Paulo) after a period of 5, 6 and 9years, respectively, aimed at verifying the stability of the COPD diagnosis over time, the evolution of the disease in terms of survival, morbidity and respiratory function, and the analyses of inflammatory and genetic biomarkers in the blood. Some questions were added to the original questionnaire and death certificates were obtained from the national official registries. ResultsThe fieldwork has been concluded in the three centers. From the original samples in the PLATINO study phasei, we were able to locate and interview 85.6% of patients in Montevideo, 84.7% in Santiago and 77.7% in São Paulo. Individuals who could not be located had higher education levels in Brazil, and were more likely to be current smokers in Santiago and São Paulo than in Montevideo. The overall quality of spirometries was ≥80% according to American Thoracic Society criteria. The number of deaths was 71 (Montevideo), 95 (Santiago) and 135 (São Paulo), with death certificates obtained from the national mortality registries for 76.1%, 88.3% and 91.8% of cases in Montevideo, Santiago and São Paulo, respectively. ConclusionsThis study shows that is possible to perform population-based longitudinal studies in Latin American with high follow-up rates and high-quality spirometry data. The adequacy of national mortality registries varies among centers in Latin America.

The natural course of sensitization and allergic diseases from childhood to adulthood

Longitudinal prospective population-based birth cohort studies of the natural history of sensitization and allergic diseases from childhood to adulthood are few. The aim of the present prospective study was to investigate the natural course of sensitization and allergic diseases in a random population-based sample of 276 children from a 1-year birth cohort of unselected Danish children followed from birth to 26 years of age. Questionnaire-based interviews, physical examination, skin prick tests, specific IgE testing, and from 10 years also spirometry, were carried out at 1.5, 5, 10, 15 and 26 years of age. Predefined diagnostic criteria were used. Follow-up rates were high, 193 (70%) attended the 26-year follow-up. The prevalence of current eczema was stable during childhood; 13% (1.5 yrs.), 9.2% (5 yrs.), 10.8% (10 yrs.), and 9.8% (15 yrs.), and 5.7% at 26 yrs. From birth to 26 years the cumulative prevalence of eczema, food allergy, asthma, and rhinoconjunctivitis was 23.5%, 13.8%, 17%, and 27.9% respectively. More than half of the participants had one or more allergic disease in the period between birth and 26 years of age. The rates of sensitization (S-IgE = 0.35 kU/l) were 8%, 23%, 26%, 32%, and 31% at 1.5, 5, 10, 15, and 26 years of age, respectively. Sensitization to food allergens was most prevalent in early infancy, whereas sensitization to inhalant allergens dominated later on. The results support the concept of the allergic march. Allergic diseases are not only occurring in childhood but persist into adulthood.

Medication-overuse headache

Medication-overuse headache (MOH) is a well described clinical entity. There is a growing body of knowledge on the epidemiology of MOH, risk factors, and treatment strategies. The International Headache Society updated the classification criteria for MOH. Population-based studies provided an insight into the prevalence and peculiarities of MOH patients in eastern Europe and Asia. Large-scaled population-based longitudinal studies made it possible to analyze risk factors leading to the development of MOH. Imaging studies helped to better understand the pathophysiology of headache chronicity. New treatment strategies have been suggested. MOH is a common headache disorder and a serious public health problem all over the world. Although the treatment regimen for MOH patients is straightforward and the outcomes are favorable, it is time now to move forward and establish a predictive model for early recognition of patients at high risk, to intervene early and avoid development of chronic headache.

Frequency of Pediatric Acute Respiratory Tract Infections in Iran; A Systematic Review

Introduction: Acute respiratory infections (ARIs) continue as the leading cause of mortality in under 5-year-old children worldwide. We decided to review available data about the incidence and prevalence of all diseases included in this category in Iran. Methods: A systematic review was designed to obtain related data from English and Farsi sources, published or unpublished. An internet search of known data sources and websites of Iranian medical universities was conducted. In addition, we reviewed abstract books of related Persian seminars and prevalence reports of ARI in children from different departments in the Ministry of Health and Medical Education of Iran. After deleting duplicates obtained material was evaluated by two epidemiologists and selected documents underwent quality assessment through data extraction checklists. We have included the most valid studies in this review. Results: Only 19 out of 98 documents reported frequency of a disease in a defined population, a group of outpatients, or hospitalized patients. Almost all of the studies had some limitations. In addition, there were no similarities in methods or place/time to make a summary on any ARIs frequency. So, we discussed each study, separately. Conclusion: Available data about frequency of ARIs in Iran were not beneficial enough to calculate burden of related diseases and make decision analysis for suggested interventions. Valid and large longitudinal population-based studies should be designed in different regions of the country supported by the Ministry and research centers.

Respiratory Viruses in Hospitalized Children with Influenza-Like Illness during the H1n1 2009 Pandemic in Sweden

BackgroundThe swine-origin influenza A(H1N1)pdm09 pandemic of 2009 had a slower spread in Europe than expected. The human rhinovirus (HRV) has been suggested to have delayed the pandemic through viral interference. The importance of co-infections over time during the pandemic and in terms of severity of the disease needs to be assessed.ObjectiveThe aim of this study was to investigate respiratory viruses and specifically the presence of co-infections with influenza A(H1N1)pdm09 (H1N1) in hospitalized children during the H1N1 pandemic. A secondary aim was to investigate if co-infections were associated with severity of disease.MethodsA retrospective study was performed on 502 children with influenza-like illness admitted to inpatient care at a pediatric hospital in Stockholm, Sweden during the 6 months spanning the H1N1 pandemic in 2009. Respiratory samples were analyzed for a panel of 16 viruses by real-time polymerase chain reaction.ResultsOne or more viruses were detected in 61.6% of the samples. Of these, 85.4% were single infections and 14.6% co-infections (2–4 viruses). The number of co-infections increased throughout the study period. H1N1 was found in 83 (16.5%) children and of these 12 (14.5%) were co-infections. HRV and H1N1 circulated to a large extent at the same time and 6.0% of the H1N1-positive children were also positive for HRV. There was no correlation between co-infections and severity of disease in children with H1N1.ConclusionsViral co-infections were relatively common in H1N1 infected hospitalized children and need to be considered when estimating morbidity attributed to H1N1. Population-based longitudinal studies with repeated sampling are needed to improve the understanding of the importance of co-infections and viral interference.

Is there a (transracial) adoption achievement gap?

Abstract In one of the first longitudinal population-based studies examining adopted children's educational achievement, we analyze whether there is a test-score gap between children in adoptive families and children in biological families. Using data from the Early Childhood Longitudinal Study, we find in aggregate adopted children have lower reading and math scores than their counterparts living in biological families. Yet there is significant variation among adoptive families by their race and health status. On one hand adoptive parents tend to be White and have more economic capital than their non-adoptive counterparts potentially contributing to educational advantages. However adopted children are also more likely to have special educational needs, contributing to greater educational disadvantages. Untangling these variables through a multivariate regression analysis, we find that transracially adopted children have similar test scores to White children living with biological parents. We point to the interaction between race, family resources and children's health status and how these characteristics differentially shape achievement outcomes for adopted children.

A Population-Based Clinicopathological Study in the Oldest-Old: The 90+ Study

Population-based longitudinal clinicopathological studies provide an ideal opportunity to study a variety of risk and protective factors in relation to pathology associated with dementia in individuals who are representative of the general population. The 90+ Study is a population-based study designed specifically to study aging and dementia as well as its neuropathological correlates in participants 90 years of age and older. We present demographic and pathological data on the first 104 participants to come to autopsy from the brain donation component of the study, The 90+ Autopsy Study. Cognitive diagnosis was assigned according to diagnostic and statistical manual 4th edition criteria for dementia and neuropathological diagnoses were made according to the Consortium to Establish a Registry for Alzheimer's Disease protocol. Dementia was present in 61% of autopsied participants, the majority of whom were diagnosed with Alzheimer's disease (85%). Many different types of pathology typically associated with dementia were common in the oldest-old, and included neurofibrillary tangles, neuritic plaques, diffuse plaques, Lewy bodies, hippocampal sclerosis, and cerebral infarctions. Most types of pathology were more frequently found in participants suffering from dementia but there was extensive overlap in pathology among those with and without dementia. In addition, 22% of demented participants did not have sufficient pathology to account for their cognitive loss. Our results highlight the poor associations between these common pathological lesions and dementia in the oldest-old and the importance of considering many different types of pathology, possibly including some yet to be identified, in order to account for all dementias in the oldest-old.

Measuring molecular biomarkers in epidemiologic studies: laboratory techniques and biospecimen considerations

The future of personalized medicine depends on the ability to efficiently and rapidly elucidate a reliable set of disease-specific molecular biomarkers. High-throughput molecular biomarker analysis methods have been developed to identify disease risk, diagnostic, prognostic, and therapeutic targets in human clinical samples. Currently, high throughput screening allows us to analyze thousands of markers from one sample or one marker from thousands of samples and will eventually allow us to analyze thousands of markers from thousands of samples. Unfortunately, the inherent nature of current high throughput methodologies, clinical specimens, and cost of analysis is often prohibitive for extensive high throughput biomarker analysis. This review summarizes the current state of high throughput biomarker screening of clinical specimens applicable to genetic epidemiology and longitudinal population-based studies with a focus on considerations related to biospecimens, laboratory techniques, and sample pooling.

Glucose control in diabetes: which target level to aim for?

The most important goal in the treatment of patients with diabetes is to lower the risk of long-term diabetes complications. Hyperglycaemia is the most important risk factor for microvascular complications in diabetes, but, in addition to hyperglycaemia, several other risk factors, particularly dyslipidaemia, elevated blood pressure and smoking, also determine the risk of macrovascular complications. In this review, we present evidence from longitudinal population-based studies that hyperglycaemia is an important risk factor for long-term complications of diabetes and discuss the results from clinical trials of the effects of the treatment of hyperglycaemia on the prevention of long-term micro- and macrovascular complications in type 1 and type 2 diabetes. An HbA(1c) target of <7.0% for the treatment of diabetes is generally accepted on the basis of evidence from several trials, whereas a target of <6.5% may be reasonable for patients with a short duration of type 2 diabetes and without extensive atherosclerosis.

Reproductive Factors and Serum Uric Acid Levels in Females from the General Population: The KORA F4 Study

ObjectiveHyperuricemia is associated with an increased risk of metabolic and cardiovascular diseases. There are pronounced sex differences in the levels of uric acid. It is largely unknown whether or not reproductive parameters which induce hormonal changes are responsible for this. We examined if there are associations between reproductive parameters and uric acid levels in a female population-based sample.MethodsIn this cross-sectional analysis, data of 1530 women aged 32 to 81 years participating in the KORA F4 study, conducted between 2006 and 2008 in Southern Germany were used. Reproductive parameters were obtained by standardized interviews. Uric acid levels were tested by the uricase method. The whole study sample and stratified in pre- and postmenopausal women was analyzed.ResultsMenopausal status and earlier age at menarche were associated with higher serum uric acid levels (age-adjusted: p-values 0.003, <0.001 respectively; after multivariable adjustment, including BMI: p-values 0.002, 0.036). A history of oral contraceptive use showed an association with uric acid levels only after multivariable adjustment (p-value 0.009). Hot flushes showed an association with uric acid levels only after age-adjustment (p-value 0.038), but lost significance after adding other confounders. Other reproductive factors, including parity, current or ever use of hormone replacement therapy, current use of oral contraceptives, hysterectomy, bilateral oophorectomy, or depressive mood related to menopausal transition were not associated with uric acid levels.ConclusionsPostmenopausal status, earlier age at menarche and a history of oral contraceptive use were independently associated with higher serum uric acid concentrations in women from the general population. Further studies, especially longitudinal population-based studies investigating the relationship of female reproductive parameters with uric acid levels are necessary to confirm our findings.