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PubMed1997

Comparison of reported prevalences of recent asthma in longitudinal and cross-sectional studies.

A potential source of bias in prevalence rates reported for symptoms and diagnoses of asthma in longitudinal studies could arise if repeated questioning of subjects or previous experience of lung function and airway responsiveness tests increased awareness of respiratory symptoms. We wished to determine the extent of any such bias by comparing reported prevalence rates from a longitudinal and cross-sectional study within similar populations. The prevalences of wheezing in the last year, waking with chest tightness, waking with shortness of breath, waking with coughing, having an attack of asthma in the last year, and current use of medications for asthma were determined using identical questions in two populations. Self-completed questionnaire responses of 946 subjects, 21 yrs of age, participating in the seventh respiratory assessment in the longitudinal Dunedin Multidisciplinary Health and Development Research Study were compared with responses provided by 991 subjects, aged 20-22 yrs, completing a postal questionnaire on one occasion only for the New Zealand section of the European Community Respiratory Health Study. The prevalence rates were not significantly different between the two populations, for all of the reported symptoms and for medication use. Differences in responses between genders were similar in each study, with all responses being more common in females. We conclude that repeated questioning regarding respiratory symptoms and repeated lung function and bronchial challenge testing in a longitudinal study of asthma did not bias prevalence rates compared with those obtained in a similar population of the same age studied on only one occasion.

Adult↗
PubMed1998

Longitudinal predictors of airway responsiveness to distilled water: the role of atopy and maternal smoke exposure.

Airway responsiveness is an objectively measurable clinical trait related to the presence of asthma. Although risk factors for this trait have been evaluated cross-sectionally, little is known about its longitudinal predictors. A population cohort of 539 children, aged 8 yrs at the start of follow-up, underwent 3-7 bronchial challenge tests spaced at 3-9 month intervals. Airway responsiveness was assessed by a single-step distilled water challenge. To investigate responsiveness as a continuous trait, the ratio of the postchallenge to prechallenge forced expiratory volume in one second was calculated. A child's repeated ratios were then regressed on the time of follow-up. The resulting child-specific regression coefficient was the outcome variable to assess longitudinal predictors of airway responsiveness (AR). Results were based on 2,267 repeated challenge tests, and indicated an overall decrease in responsiveness. Children with a diagnosis of asthma (mean+/-SD, longitudinal change in AR + yr(-1): -0.060+/-0.149), those with a positive skin-prick test (-0.018+/-0.106) and those with reported exposure to maternal smoking (-0.004+/-0.083) demonstrated increased airway responsiveness over time. All of these changes in airway responsiveness were found to be significant in multiple linear regression analysis (p<0.05). Stratified analysis further indicated that the effect of maternal smoking was observed primarily in nonatopic children and was greatest at an exposure level of > or =10 cigarettes x day(-1). In conclusion, atopy and exposure to maternal smoking can predict longitudinal change in childhood airway responsiveness.

Air Pollutants↗
PubMed2003

Genome-wide linkage analysis of longitudinal phenotypes using sigma2A random effects (SSARs) fitted by Gibbs sampling.

The study of change in intermediate phenotypes over time is important in genetics. In this paper we explore a new approach to phenotype definition in the genetic analysis of longitudinal phenotypes. We utilized data from the longitudinal Framingham Heart Study Family Cohort to investigate the familial aggregation and evidence for linkage to change in systolic blood pressure (SBP) over time. We used Gibbs sampling to derive sigma-squared-A-random-effects (SSARs) for the longitudinal phenotype, and then used these as a new phenotype in subsequent genome-wide linkage analyses. Additive genetic effects (sigma2A.time) were estimated to account for approximately 9.2% of the variance in the rate of change of SBP with age, while additive genetic effects (sigma2A) were estimated to account for approximately 43.9% of the variance in SBP at the mean age. The linkage results suggested that one or more major loci regulating change in SBP over time may localize to chromosomes 2, 3, 4, 6, 10, 11, 17, and 19. The results also suggested that one or more major loci regulating level of SBP may localize to chromosomes 3, 8, and 14. Our results support a genetic component to both SBP and change in SBP with age, and are consistent with a complex, multifactorial susceptibility to the development of hypertension. The use of SSARs derived from quantitative traits as input to a conventional linkage analysis appears to be valuable in the linkage analysis of genetically complex traits. We have now demonstrated in this paper the use of SSARs in the context of longitudinal family data.

Adult↗
PubMed2003

Power of linkage analysis using traits generated from simulated longitudinal data of the Framingham Heart Study.

The Framingham Heart Study is a very successful longitudinal research for cardiovascular diseases. The completion of a 10-cM genome scan in Framingham families provided an opportunity to evaluate linkage using longitudinal data. Several descriptive traits based on simulated longitudinal data from the Genetic Analysis Workshop 13 (GAW13) were generated, and linkage analyses were performed for these traits. We compared the power of detecting linkage for baseline and slope genes in the simulated data of GAW13 using these traits. We found that using longitudinal traits based on multiple follow-ups may not be more powerful than using cross-sectional traits for genetic linkage analysis.

Adult Children↗
PubMed2006

Linkage analysis of longitudinal data and design consideration.

BACKGROUND: Statistical methods have been proposed recently to analyze longitudinal data in genetic studies. So far, little attention has been paid to examine the relationship among key factors in genetic longitudinal studies including power, the number of families or sibships, and the number of repeated measures per individual subjects. RESULTS: We proposed a variance component model that extends classic variance component models for a single quantitative trait to mapping longitudinal traits. Our model includes covariate effects and allows genetic effects to vary over time. Using our proposed model, we examined the power, pedigree structures, and sample size through simulation experiments. CONCLUSION: Our simulation results provide useful insights into the study design for genetic, longitudinal studies. For example, collecting a small number of large sibships is much more powerful than collecting a large number of small sibships or increasing the number of repeated measures, when the total number of measurements is comparable.

Computer Simulation↗
PubMed1992

Long-term longitudinal measurements of plasma dehydroepiandrosterone sulfate in normal men.

Dehydroepiandrosterone sulfate (DS) was measured by direct tritium RIA in longitudinal plasma specimens from 97 normal healthy male participants in the Baltimore Longitudinal Study of Aging. Fasting blood was collected at regular visits (approximately 1.5 yr apart) over an average 13 yr of adulthood (cumulative age range: 32-83 yr). DS was measured in 3-4 widely spaced specimens from each subject. A decline in DS was found in 65 (67%) subjects, 13 subjects (13%) showed no change, and increases were found in the 19 remaining subjects during the study period. A plot of individual data points revealed the same pattern we had obtained previously from a cross-sectional study of a different normal male population. A plot of DS values vs. age among subjects whose DS increased during the study also revealed an age-related decline. Thus, the longitudinal decrease in circulating DS, long inferred from cross-sectional data, is confirmed for normal men in the present study. A more detailed study of every specimen collected during the study period from 12 of the Baltimore Longitudinal Study of Aging subjects (4 whose values tended to be low, 4 whose values tended to be high, and 4 whose values were near the mean) failed to reveal any patterns of variation that could be correlated with changes in life circumstances, health status, or any other discernible factors. Hence, the wide variability seen in DS among individuals within normal populations remains unexplained.

Adult↗
PubMed2002

Longitudinal study of vasopressin-cell antibodies and of hypothalamic-pituitary region on magnetic resonance imaging in patients with autoimmune and idiopathic complete central diabetes insipidus.

Diagnosis of autoimmune central diabetes insipidus (CDI) is based on the presence of autoantibodies to AVP-secreting cells (AVPcAb) or the coexistence of other autoimmune polyendocrine syndromes; moreover, it can be also suggested by the presence of lymphocytic infundibulo-neurohypophysitis, evidenced by biopsy of pituitary stalk and/or by pituitary stalk thickening on magnetic resonance imaging (MRI). However, so far, in clinical CDI patients with lymphocytic infundibulo-neurohypophysitis, AVPcAb have not been investigated and in those with or without autoimmune polyendocrine syndromes (APS), longitudinal studies on the behavior of AVPcAb alone, or of both AVPcAb and hypothalamic pituitary imaging on MRI are lacking. Aim of this work was to investigate in these patients the occurrence of AVPcAb (by indirect immunofluorescence) and of pituitary stalk thickening (by MRI) and their longitudinal changes during a follow-up period. We studied 22 patients, aged 29-53, with APS and complete CDI, grouped as follows: 10 with recent onset (< or =1.5 yr) of CDI (group 1a) and 12 with CDI of long-term duration (> or = 7 yr) (group 1b); moreover, a group of 13 patients with apparent idiopathic CDI of recent onset (<1.5 yr) were studied. They were divided, on the basis of the detection of AVPcAb as follows: 5 AVPcAb positive patients (aged 19-26) classified as isolated autoimmune CDI (group 2) and 8 AVPcAb negative patients (aged 21-26), classified as true idiopathic CDI (group 3). All patients were evaluated yearly, along 5 yr, for AVPcAb and for hypothalamic-pituitary region imaging. At study entry, 8/10 (80%) of patients in group 1a and 7/12 (58.3%) in group 1b were positive for AVPcAb and persisted positive subsequently, during all the follow-up period, even if at lower titers. All patients in group 2 were positive and all those in group 3 were negative for AVPcAb and persisted positive and negative, respectively, for all the follow-up study. Among the AVPcAb-positive patients, only 5 in group 1a and 2 in group 2 showed also pituitary stalk thickening at the first observations, which however spontaneously disappeared subsequently indicating a possible lymphocytic infundibulo-neurohypophysitis. All patients in the studied groups showed loss of the hyperintense signal of the neurohypophysis on MRI at entry and during all the follow-up period. Results of this longitudinal study suggest: 1) AVPcAb, frequently present at high titers in recent phases of CDI, persist subsequently, even if at lower titers, several years after the onset of disease. 2) The occurrence of a lymphocytic infundibulo-neurohypophysitis suggested by the pituitary stalk thickening on MRI only in patients positive for AVPcAb confirms a further autoimmune variant of CDI also in these cases. 3) The longitudinal behavior of patients in group 3 suggests that the absence of AVPcAb at the onset of clinical idiopathic CDI is able to exclude a subsequent appearance of these antibodies and consequently an autoimmune involvement in CDI of these patients. Instead the finding of AVPcAb in several patients with only CDI, thought at first clinical observation as idiopathic, indicates that the prevalence of autoimmune CDI must be considered much higher than that so far reported.

Adult↗
PubMed2005

Normative estimates of cross-sectional and longitudinal brain volume decline in aging and AD.

OBJECTIVE: To test the hypotheses 1) that whole-brain volume decline begins in early adulthood, 2) that cross-sectional and longitudinal atrophy estimates agree in older, nondemented individuals, and 3) that longitudinal atrophy accelerates in the earliest stages of Alzheimer disease (AD). METHODS: High-resolution, high-contrast structural MRIs were obtained from 370 adults (age 18 to 97). Participants over 65 (n = 192) were characterized using the Clinical Dementia Rating (CDR) as either nondemented (CDR 0, n = 94) or with very mild to mild dementia of the Alzheimer type (DAT, CDR 0.5 and 1, n = 98). Of these older participants, 79 belonged to a longitudinal cohort and were imaged again a mean 1.8 years after baseline. Estimates of gray matter (nGM), white matter (nWM), and whole-brain volume (nWBV) normalized for head sizes were generated based on atlas registration and image segmentation. RESULTS: Hierarchical regression of nWBV estimates from nondemented individuals across the adult lifespan revealed a strong linear, moderate quadratic pattern of decline beginning in early adulthood, with later onset of nWM than nGM loss. Whole-brain volume differences were detected by age 30. The cross-sectional atrophy model overlapped with the rates measured longitudinally in older, nondemented individuals (mean decline of -0.45% per year). In those individuals with very mild DAT, atrophy rate more than doubled (-0.98% per year). CONCLUSIONS: Nondemented individuals exhibit a slow rate of whole-brain atrophy from early in adulthood with white-matter loss beginning in middle age; in older adults, the onset of dementia of the Alzheimer type is associated with a markedly accelerated atrophy rate.

Adolescent↗
PubMed2000

Age-specific incidence rates of Alzheimer's disease: the Baltimore Longitudinal Study of Aging.

OBJECTIVE: To estimate age-specific incidence rates of AD in the Baltimore Longitudinal Study of Aging (BLSA). BACKGROUND: The BLSA is a volunteer cohort of normal subjects followed longitudinally with biennial evaluations at the Gerontology Research Center of the National Institute on Aging. METHODS: Subjects are 1236 participants (802 men, 434 women) in the BLSA with longitudinal follow-up between January 1985 and May 1998. The average length of follow-up was 7.5 years, with participants evaluated every 2 years by physical, neurologic, and neuropsychological examinations. Using Diagnostic and Statistical Manual of Mental Disorders, 3rd ed., revised and National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria, the authors diagnosed dementia and AD. RESULTS: The authors diagnosed 155 cases of dementia, of which 114 (74%) were AD. Incidence rates of AD increased with age from an estimated 0.08% per year (95% CI 0.00 to 0.43) in the 60 to 65 age group to an estimated 6.48% per year (95% CI 5.01 to 8.38) in the 85+ age group for men and women combined. The doubling time of incidence rates was estimated to be approximately 4.4 years and the median time of conversion from mild cognitive impairment to diagnosis of AD was estimated to be 4.4 years. There was a trend for women to have higher incidence rates than men and for fewer years of education to be associated with higher incidence rates; however, these effects were not significant. CONCLUSION: Incidence rates for AD in the BLSA are consistent with published rates in other studies. The longitudinally followed subjects of the BLSA offer a unique opportunity to prospectively investigate the antecedents of AD.

Age Factors↗
PubMed2005

Longitudinal modeling of adiposity in periadolescent Greek schoolchildren.

PURPOSE: Obesity has an etiology that is multidimensional in nature. Given the dearth of longitudinal data, we examined changes in adipose tissue (Ad) in relation to physical activity levels (PA), aerobic fitness (AF), and energy intake (EI) in Greek schoolchildren, as they progressed from age 12 to 14 yr. METHODS: This was a 2-yr and three-time-point (TP) study. Participants (N=210 (TP1); =204 (TP2); =198 (TP3)) were assessed for anthropometry, maturity status, Ad, PA, AF, and EI. Mean values were used for exploratory analyses, whereas two generalized estimating equations (GEE) models examined for longitudinal associations between the studied parameters. The first (GEE1) aimed to extract inherent associations between the dependent (Ad) and independent (PA, AF, EI) variables for the entire study period. For further evidence of association, the second analysis (GEE2) used the independent variables at TP1 and TP2 to predict the dependent variables at TP3. RESULTS: Levels of Ad in boys decreased significantly (P<0.05) from TP1 to TP3, whereas the same variable demonstrated a nonsignificant increase (P>0.05) in girls. GEE1 revealed that longitudinal changes in Ad were significantly associated only with PA (beta=-0.16; P<0.001) and AF (beta=-0.09; P<0.05) for all schoolchildren. Similarly, GEE2 revealed that the main factors (at TP1 and TP2) predicting the development of Ad (at TP3) were PA (beta=-0.14; P<0.001) followed by AF (beta=-0.10; P<0.05). CONCLUSION: With respect to data presented, we established that longitudinal changes in Ad are mainly accompanied by changes in PA and, to a lesser extent, AF levels.

Adiposity↗
PubMed2001

The shortened Study Process Questionnaire: an investigation of its structure and longitudinal stability using confirmatory factor analysis.

BACKGROUND: The Study Process Questionnaire (SPQ) is a widely used measure of learning approach and was proposed to have three orientations: surface, deep, and achieving, each with an underlying motive and strategy. AIMS: This study aimed to examine the factor structure and longitudinal stability over five to seven years of a modified shortened 18-item version of the SPQ. SAMPLES: A total of 1349 medical students completed the shortened SPQ at application and in their final year of medical school. Three additional cohorts of students completed the shortened SPQ during their third and fourth year of medical school (sample size: 194, 203, 174). METHOD: Confirmatory factor analysis was used to examine the dimensionality and longitudinal stability of the shortened SPQ. RESULTS: Like the full 42-item version, the shortened SPQ has six subscales and the data are best fit by three second order shared indicator factors (surface, deep and achieving) and a single higher order composite deep-achieving factor. The longitudinal analysis found 26.8%, 26.3%, and 18.7% of the non-attenuated variance of the surface, deep and achieving factor scores in the final year is predicted from the shortened SPQ completed at application to medical school. CONCLUSIONS: The shortened 18-item SPQ has the same six subscales as the full SPQ as well as three second order shared indicator factors (surface, deep, achieving) and one higher order deep-achieving factor similar to that suggested by Biggs (1987). The longitudinal analysis supports this hypothesis and suggests that these learning approaches are partly stable during medical school undergraduate training and partly modifiable under the influence of the educational environment.

Adult↗
PubMed2001

Three-mode models for multivariate longitudinal data.

Multivariate longitudinal data are characterized by three modes: variables, occasions and subjects. Three-mode models are described as special cases of a linear latent variable model. The assumption of measurement invariance across occasions yields three-mode models that are suited for the analysis of multivariate longitudinal data. These so-called longitudinal three-mode models include autoregressive models and latent curve models as special cases. Empirical data from the field of industrial psychology are used in an example of how to test substantive hypotheses with the longitudinal, autoregressive and latent curve three-mode models.

Adult↗
PubMed2004

Accumulation of calcium in human common iliac artery, aortic valve, xiphoid process, costal cartilage, posterior longitudinal ligament, trigeminal nerve, and rib accompanied by increase of magnesium.

To examine whether an accumulation of Ca in the tissues was accompanied by an increase of Mg, the authors investigated the relationships between Ca and Mg contents in the common iliac arteries, aortic valves, xiphoid processes, costal cartilages, posterior longitudinal ligaments, trigeminal nerves, and ribs by inductively coupled plasma-atomic emission spectrometry. After the ordinary dissections by medical students were finished, the common iliac arteries, aortic valves, xiphoid processes, bilateral the fourth costal cartilages, posterior longitudinal ligaments between the fourth and fifth cervical vertebrae, trigeminal nerves, and bilateral the sixth ribs were resected from the subjects and elements were determined. It was found that there were extremely significant direct correlations between Ca and Mg contents in all of the common iliac arteries, aortic valves, costal cartilages, posterior longitudinal ligaments, and trigeminal nerves, whereas there were significant direct correlations in both the xiphoid processes and ribs. As for the tissues containing Ca higher than 20 mg/g, the average mass ratios of Mg/Ca were similar among the seven tissues. As Ca increased in all of the common iliac arteries, aortic valves, xiphoid processes, costal cartilages, posterior longitudinal ligaments, trigeminal nerves, and ribs, Mg increased simultaneously in the seven tissues.

Aged↗
PubMed2005

Ossification of the posterior longitudinal ligament. Results of anterior cervical decompression and arthrodesis in sixty-one North American patients.

BACKGROUND: Ossification of the posterior longitudinal ligament is commonly associated with cervical myelopathy. Surgical treatment is a matter of controversy. We report on a series of patients who were managed with anterior cervical decompression and arthrodesis for the treatment of cervical myelopathy associated with ossification of the posterior longitudinal ligament. METHODS: We retrospectively reviewed the records for all sixty-five patients who had been managed with anterior decompression and arthrodesis for the treatment of cervical ossification of the posterior longitudinal ligament and associated neurologic compression from 1982 to 2001. Sixty-one patients (thirty-nine men and twenty-two women) were followed for at least two years (or until the time of death). The average number of vertebrae resected was 2.2. The average duration of follow-up for the sixty surviving patients was four years (range, two years to fifteen years and four months). The preoperative, six-week postoperative, and final follow-up clinical status (including neurological function as assessed with the Nurick grading system) was recorded for each patient. RESULTS: Fifty-six of the sixty-one patients had neurological improvement, with an average improvement of 1.5 Nurick grades at the time of the final follow-up. Eight patients had absent dura at the time of surgery and, of these, five had development of a cerebrospinal fluid fistula. Eight patients had development of new neurological signs and/or symptoms in the upper extremity postoperatively. Eight patients required reoperation because of a painful pseudarthrosis (one patient), strut-graft dislodgment (three), cerebrospinal fluid leakage (three), or compression of a nerve root caudad to the area of the original procedure (one). One patient died as the result of cardiac arrest on the third postoperative day. Fifty-eight patients had an osseous fusion, one had an asymptomatic nonunion, and one had a symptomatic pseudarthrosis that was treated with revision surgery. CONCLUSIONS: Anterior decompression and arthrodesis is an effective way to achieve pain relief and neurological improvement in North American patients of non-Asian descent who have cervical myelopathy associated with ossification of the posterior longitudinal ligament. The risk of durocutaneous fistula, graft dislodgment, and postoperative neurological symptoms appears to be high in patients with cervical myelopathy associated with this condition.

Arthrodesis↗
PubMed2004

Longitudinal versus cross-sectional methodology for estimating the economic burden of breast cancer: a pilot study.

BACKGROUND: Projecting future breast cancer treatment expenditure is critical for budgeting purposes, medical decision making and the allocation of resources in order to maximise the overall impact on health-related outcomes of care. Currently, both longitudinal and cross-sectional methodologies are used to project the economic burden of cancer. This pilot study examined the differences in estimates that were obtained using these two methods, focusing on Maryland, US Medicaid reimbursement data for chemotherapy and prescription drugs for the years 1999-2000. METHODS: Two different methodologies for projecting life cycles of cancer expenditure were considered. The first examined expenditure according to chronological time (calendar quarter) for all cancer patients in the database in a given quarter. The second examined only the most recent quarter and constructed a hypothetical expenditure life cycle by taking into consideration the number of quarters since the respective patient had her first claim. RESULTS: We found different average expenditures using the same data and over the same time period. The longitudinal measurement had less extreme peaks and troughs, and yielded average expenditure in the final period that was 60% higher than that produced using the cross-sectional analysis; however, the longitudinal analysis had intermediate periods with significantly lower estimated expenditure than the cross-sectional data. CONCLUSIONS: These disparate results signify that each of the methods has merit. The longitudinal method tracks changes over time while the cross-sectional approach reflects more recent data, e.g. current practice patterns. Thus, this study reiterates the importance of considering the methodology when projecting future cancer expenditure.

Antineoplastic Agents↗
PubMed1991

Comparison of longitudinally and cross-sectionally determined age-related decline in spirometric measurements.

In order to compare the longitudinally and cross-sectionally determined annual decline of spirometric measurements, we measured spirograms from 326 male adults four times over five years. Acceptable results were obtained three times or more in 269 subjects aged 30 to 55 at the initial survey. Longitudinal annual changes in the height-squared proportional values of forced vital capacity (CFVC), forced expiratory volume in one second (CFEV1), and maximal expiratory flow at 50% and 25% of FVC (CVmax 50 and CVmax 25), was estimated by the model in which the effect of each individual's level was included as an explanatory variable. The cross-sectional annual change in those indices was determined by including the effect of each survey's level in the model. The longitudinal estimate of annual decline was significantly smaller than the cross-sectional estimate for all indices except CVmax 25. No evidence suggested that systemic error of measurement or a learning effect caused significant bias in the data. The discrepancy in the estimated annual changes seemed to be caused by the cohort effect in our subjects, since the cross-sectional analysis is primarily sensitive to harmful factors operating in the past. We concluded that the longitudinal data for individuals or groups should not be compared with any reference value based on a cross-sectional analysis.

Adult↗
PubMedDate not supplied

The importance of longitudinal studies in family medicine: experiences of two practice-based research networks.

BACKGROUND: For evidence-based decision making in family practice, it is essential to know the long-term (natural) course of common diseases and their outcomes under care and treatment. This article, based on a research methodology workshop, aims to raise awareness and interest in longitudinal research in practice-based research networks (PBRNs) among family physicians (FP) and researchers, and to elucidate a number of broad principles that apply to longitudinal research in such settings. METHODS: A workshop discussion of PBRN experts, based on 2 examples of PBRN-based longitudinal studies, focusing on the general methodological principles was held in March 2005 in Colorado Springs, CO. The first study, conducted in a historic cohort, documented long-term outcome of depression in 386 patients in family practice. The second study analyzed consequences of age-associated peripheral neuropathy in a concurrent follow-up study design. It was possible to prospectively follow a cohort of 604 healthy subjects enrolled in the practices by research nurses. Discussion at the workshop was generated around the following methodological topics: study designs, recruitment, retention and tracking of participants, dealing with changes in diagnostic and treatment of standards over time, informed consent, data analysis, and funding issues. RESULTS AND CONCLUSIONS: The workshop concluded that, although there are many obstacles to be overcome when conducting longitudinal studies in practice settings, the benefits for our discipline could be substantial. Concurrent and historic cohorts each have advantages and disadvantages. Although tracking patients (and physicians) over time is a challenge, periodic rewards enhance recruitment and retention. Informed consent is critical although ethical requirements may change. Use of standard well-defined definitions promotes consistency of data collection over time, as does training of FPs and staff. Data analysis has become both easier and more sophisticated, and statistical assistance is advised from the outset. Funding remains a challenge, but costs need not be prohibitive. Given its importance, PBRNs should be encouraged to develop methods of long-term data collection on cohorts of patients followed by primary care physicians.

Colorado↗
PubMed2022

Uric Acid Levels Are Associated with Bone Mineral Density in Mexican Populations: A Longitudinal Study.

Background: Inconsistent epidemiological evidence between uric acid (UA) and bone mineral density (BMD) has been observed. Therefore, we evaluated the association between UA and BMD in Mexican adults. Methods: This analysis was conducted on 1423 participants from the Health Workers Cohort Study. We explored cross-sectional associations using linear regression and longitudinal associations using fixed-effects linear regression by sex and age groups (<45 and &#x2265;45 years). Results: In females <45 years old, the cross-sectional analysis showed that UA levels were positively associated with total hip BMD. However, in the longitudinal analysis, we observed a negative association with the femoral neck and lumbar spine BMD. In contrast, in males <45 years old, we found an increase in total hip and femoral neck BMD in the groups with high levels of UA in the longitudinal association. On the other hand, in females &#x2265;45 years old, we observed a longitudinal association between UA and loss of BMD at different sites. We did not observe an association between UA levels and BMD in males &#x2265;45 years old. Conclusions: Our results suggest higher serum UA levels are associated with low BMD at different skeletal sites in Mexican females. Further studies are needed to delineate the underlying mechanisms behind this observation.

Male↗