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1.
Front Health Serv ; 3: 1220027, 2023.
Article in English | MEDLINE | ID: mdl-38077632

ABSTRACT

Background: During the Coronavirus disease (COVID-19) pandemic, countries implemented border control and quarantine measures to reduce transmission. The Alberta Border Testing Pilot Program (ABTPP) allowed international travellers entering Alberta to reduce their quarantine period following two negative COVID-19 tests. We evaluated participant experiences with the ABTPP and implementation. Method: We used a parallel convergent mixed-methods design to explore participant experiences through electronic web-based questionnaires (n = 21,089; n = 13,839) and semi-structured telephone interviews (n = 30). We evaluated implementation through three staff focus groups (n = 11). We analysed questionnaires using descriptive statistics and analysed interviews using inductive and deductive thematic analysis. We deductively coded focus group data using the 2009 Consolidated Framework for Implementation Research (CFIR). Results: Questionnaires indicated minimal issues with registration forms (91.7%), symptom reports (95.5%), and COVID-19 testing (95.7%). Most respondents (95.1%) expressed willingness to participate in the ABTPP again. Interviews revealed three themes related to participant experience: program efficiency, clarity of information, and requisite effort. Focus groups identified key implementation facilitators including the single health information system, strong stakeholder partnerships, and good communication across partnerships. Barriers included program complexity, implementation timeline, and evolving external context. Discussion: Participants reported high satisfaction with the ABTPP. Border testing programs should have high efficiency, require low effort, and use messaging that is clear and consistent. The effective implementation of border testing programs may be facilitated by strong leadership, adaptability, automated components, good communication, and simple technology. Learnings from participants and staff may help improve the implementation of border control programs for future pandemics or other emergencies. Conclusions: The ABTTP was a novel border control measure during the COVID-19 pandemic. Our evaluation of both participant and staff experiences demonstrated high levels of traveller satisfaction and identified areas for improvement that can inform the development of future border control measures.

2.
J Surg Case Rep ; 2023(5): rjad263, 2023 May.
Article in English | MEDLINE | ID: mdl-37215626

ABSTRACT

Syringocystadenoma papilliferum (SCAP) is a rare, hamartomatous tumor of the apocrine glands, which typically manifests in the head and neck region. We present a case of 60-year-old male with a several-year history of the lesion located on the abdominal wall and a second case of a 58-year-old male with a history of a slow-growing lesion located on the tragus. Despite varying presentations and locations, both patients were identified to have SCAP on pathological evaluation. Appropriate treatments of SCAP range from CO2 laser treatment to surgical excision; we recommend surgical excision due to the risk of malignant transformation.

3.
PLoS One ; 18(4): e0284631, 2023.
Article in English | MEDLINE | ID: mdl-37075057

ABSTRACT

Most terrestrial angiosperms form mutualisms with both mycorrhizal fungi and animal pollinators. Yet, the effects of mycorrhizae on pollinator behavior and plant reproduction are unknown for most species, and whether the source or type of mycorrhizal fungi affects reproductive success has rarely been examined. We examined whether inoculating highbush blueberry (Vaccinium corymbosum; Ericaceae) with ericoid mycorrhizal fungi enhanced investment in flowering and attractiveness to pollinators, and thus reduced their levels of pollen limitation over that of non-inoculated plants. We also examined the degree to which pollen limitation was dependent on inoculation source and the surrounding pollinator community context. Three-year-old saplings of Vaccinium corymbosum 'Bluecrop' or highbush blueberry (Ericaceae) were inoculated with a) ericoid mycorrhizal fungi within soil of the rhizosphere of plants growing at a local blueberry farm, b) a commercially available ericoid inoculant, c) both the local soils and commercial inoculum, or d) were not inoculated and served as controls. They were grown for one year in pots in a common garden and, in the following year, were moved to six farms in central Vermont that were known from prior studies to differ in pollinator abundance and diversity. We conducted a hand pollination experiment at each farm to examine if inoculation or pollinator abundance (i.e., farm context) affected reproductive success. Plants treated with all types of inoculums were more likely to flower, and produced more inflorescence buds than non-inoculated plants in 2018. However, in 2019, plants in the combination inoculum treatment, alone, produced more inflorescence buds than those in the other treatments. Neither the source of inoculum nor hand pollination affected fruit set (the proportion of flowers setting fruit), or fruit sugar content. Hand pollination, but not inoculation, increased berry mass and the average number of seeds produced/berry. Our results add to the growing body of evidence that mycorrhizal fungi can affect reproductive traits of their hosts but that the effects of mycorrhizal fungi depend on the mycorrhizal symbionts.


Subject(s)
Blueberry Plants , Ericaceae , Mycorrhizae , Animals , Blueberry Plants/microbiology , Reproduction , Pollination , Symbiosis , Soil , Plants
4.
J Speech Lang Hear Res ; 64(12): 4982-4999, 2021 12 13.
Article in English | MEDLINE | ID: mdl-34705529

ABSTRACT

PURPOSE: The goal of this study was to assess the listening behavior and social engagement of cochlear implant (CI) users and normal-hearing (NH) adults in daily life and relate these actions to objective hearing outcomes. METHOD: Ecological momentary assessments (EMAs) collected using a smartphone app were used to probe patterns of listening behavior in CI users and age-matched NH adults to detect differences in social engagement and listening behavior in daily life. Participants completed very short surveys every 2 hr to provide snapshots of typical, everyday listening and socializing, as well as longer, reflective surveys at the end of the day to assess listening strategies and coping behavior. Speech perception testing, with accompanying ratings of task difficulty, was also performed in a lab setting to uncover possible correlations between objective and subjective listening behavior. RESULTS: Comparisons between speech intelligibility testing and EMA responses showed poorer performing CI users spending more time at home and less time conversing with others than higher performing CI users and their NH peers. Perception of listening difficulty was also very different for CI users and NH listeners, with CI users reporting little difficulty despite poor speech perception performance. However, both CI users and NH listeners spent most of their time in listening environments they considered "not difficult." CI users also reported using several compensatory listening strategies, such as visual cues, whereas NH listeners did not. CONCLUSION: Overall, the data indicate systematic differences between how individual CI users and NH adults navigate and manipulate listening and social environments in everyday life.


Subject(s)
Cochlear Implantation , Cochlear Implants , Speech Perception , Adult , Auditory Perception , Hearing , Humans , Social Participation , Speech Perception/physiology
5.
Article in English | MEDLINE | ID: mdl-33807955

ABSTRACT

This study examines the statewide service coverage of emergency medical services (EMS) in view of public health planners, policy makers, and ambulance service managers. The study investigates the statewide service coverage in a mixed region of urban, rural, and frontier regions to address the importance of ambulance service coverage at a large scale. The study incorporated statewide road networks for ambulance travel time, census blocks for population, and backup service coverage using geographic information systems (GIS). The catchment areas were delineated by the travel time after subtracting chute time for each Census Block as an analysis zone. Using the catchment areas from the ambulance base to the centroid of Census Block, the population and land coverage were calculated. The service shortage and multiple coverage areas were identified by the catchment areas. The study found that both reducing chute time and increasing the speed of emergency vehicles at the same time was significantly more effective than improving only one of two factors. The study shows that the service is improved significantly in frontier and urban areas by increasing driving time and chute time. However, in rural areas, the improvement is marginal owing to wider distribution than urban areas and shorter threshold response time than frontier areas. The public health planners and EMS managers benefit from the study to identify underserved areas and redistribute limited public resources.


Subject(s)
Ambulances , Emergency Medical Services , Geographic Information Systems , Humans , Rural Population , Travel
6.
J Acoust Soc Am ; 149(2): 1224, 2021 02.
Article in English | MEDLINE | ID: mdl-33639827

ABSTRACT

This study assessed the impact of semantic context and talker variability on speech perception by cochlear-implant (CI) users and compared their overall performance and between-subjects variance with that of normal-hearing (NH) listeners under vocoded conditions. Thirty post-lingually deafened adult CI users were tested, along with 30 age-matched and 30 younger NH listeners, on sentences with and without semantic context, presented in quiet and noise, spoken by four different talkers. Additional measures included working memory, non-verbal intelligence, and spectral-ripple detection and discrimination. Semantic context and between-talker differences influenced speech perception to similar degrees for both CI users and NH listeners. Between-subjects variance for speech perception was greatest in the CI group but remained substantial in both NH groups, despite the uniformly degraded stimuli in these two groups. Spectral-ripple detection and discrimination thresholds in CI users were significantly correlated with speech perception, but a single set of vocoder parameters for NH listeners was not able to capture average CI performance in both speech and spectral-ripple tasks. The lack of difference in the use of semantic context between CI users and NH listeners suggests no overall differences in listening strategy between the groups, when the stimuli are similarly degraded.


Subject(s)
Cochlear Implantation , Cochlear Implants , Speech Perception , Adult , Hearing , Humans , Semantics
7.
Front Neurol ; 12: 724800, 2021.
Article in English | MEDLINE | ID: mdl-35087462

ABSTRACT

Objective: Speech tests assess the ability of people with hearing loss to comprehend speech with a hearing aid or cochlear implant. The tests are usually at the word or sentence level. However, few tests analyze errors at the phoneme level. So, there is a need for an automated program to visualize in real time the accuracy of phonemes in these tests. Method: The program reads in stimulus-response pairs and obtains their phonemic representations from an open-source digital pronouncing dictionary. The stimulus phonemes are aligned with the response phonemes via a modification of the Levenshtein Minimum Edit Distance algorithm. Alignment is achieved via dynamic programming with modified costs based on phonological features for insertion, deletions and substitutions. The accuracy for each phoneme is based on the F1-score. Accuracy is visualized with respect to place and manner (consonants) or height (vowels). Confusion matrices for the phonemes are used in an information transfer analysis of ten phonological features. A histogram of the information transfer for the features over a frequency-like range is presented as a phonemegram. Results: The program was applied to two datasets. One consisted of test data at the sentence and word levels. Stimulus-response sentence pairs from six volunteers with different degrees of hearing loss and modes of amplification were analyzed. Four volunteers listened to sentences from a mobile auditory training app while two listened to sentences from a clinical speech test. Stimulus-response word pairs from three lists were also analyzed. The other dataset consisted of published stimulus-response pairs from experiments of 31 participants with cochlear implants listening to 400 Basic English Lexicon sentences via different talkers at four different SNR levels. In all cases, visualization was obtained in real time. Analysis of 12,400 actual and random pairs showed that the program was robust to the nature of the pairs. Conclusion: It is possible to automate the alignment of phonemes extracted from stimulus-response pairs from speech tests in real time. The alignment then makes it possible to visualize the accuracy of responses via phonological features in two ways. Such visualization of phoneme alignment and accuracy could aid clinicians and scientists.

8.
J Speech Lang Hear Res ; 63(11): 3847-3854, 2020 11 13.
Article in English | MEDLINE | ID: mdl-33049146

ABSTRACT

Purpose The goal of this study was to develop and validate a new corpus of sentences without semantic context to facilitate research aimed at isolating the effects of semantic context in speech perception. Method The newly developed corpus contains nonsensical sentences but is matched in vocabulary and syntactic structure to the existing Basic English Lexicon (BEL) corpus. It consists of 20 lists, with each list containing 25 sentences and each sentence having four keywords. Each new list contains the same keywords as the respective list in the original BEL corpus, but the keywords within each list are scrambled across sentences to eliminate semantic context within each sentence, while maintaining the original syntactic structure. All sentences in the original and nonsense BEL corpora were recorded by the same two male and two female talkers. Results Mean intelligibility scores for each list were estimated by calculating the mean proportion of correct keywords achieved by 40 normal-hearing listeners for one male and one female talker. Although small but significant differences were found between some pairs of lists, mean performance for all 20 lists fell within the 95% confidence intervals of the mean. Conclusions Lists in the newly developed nonsense corpus are reasonably well equated for difficulty and can be used interchangeably in a randomized experimental design. Both the original and nonsense BEL sentences, all recorded by the same four talkers, are publicly available. Supplemental Material https://doi.org/10.23641/asha.13022900.


Subject(s)
Semantics , Speech Perception , Female , Hearing Tests , Humans , Language , Male , Vocabulary
9.
Prev Med ; 141: 106292, 2020 12.
Article in English | MEDLINE | ID: mdl-33075351

ABSTRACT

Mental health difficulties are childhood-onset with lifelong health, social and economic consequences. Children spend a large amount of time in schools, making schools an important context for mental health prevention and support. We examine how school composition and school climate, controlling for individual child-level characteristics, are associated with children's mental health difficulties (emotional and behavioural difficulties). Data from 23,215 children from 648 primary schools in England were analysed to examine the associations of school composition (size, gender, socioeconomic and ethnicity) and school climate with mental health (emotional symptoms, behavioural symptoms and above clinical cut-off scores) adjusting for individual child socio-demographic characteristics. We find that between 3% and 4.5% of the variation in children's mental health outcomes could be attributed to schools. Of this, small proportions were explained by school composition (1.4 to 3.8%) and larger proportions were explained by school climate (29.5 to 48.8%). Lower school socio-economic status was associated with higher behavioural symptoms (coef = 0.02 [95%CI: 0.01-0.04]) and slightly raised odds of high mental health difficulties (OR = 1.05, 95% CI: 1.01,1.09). More positive school climate was associated with lower emotional (coef = -0.09 [95%CI:-0.11,-0.08]) and behavioural (coef = -0.13 [95% CI,-0.15:-0.11]) symptoms and lower odds of mental health difficulties (OR = 0.78, 95%CI:0.74,0.81). Some associations between school factors and mental health were moderated by child sex and SES. School composition factors were weakly associated with children's mental health, whereas school climate explained a larger amount of between-school variation and appears a good target for universal prevention of mental health difficulties in children.


Subject(s)
Mental Health , Schools , Child , Child Health , Emotions , England/epidemiology , Humans
10.
J Assoc Res Otolaryngol ; 21(4): 393, 2020 08.
Article in English | MEDLINE | ID: mdl-32748101

ABSTRACT

An error in interpreting the statistical analysis output led to reporting errors in some of the effect sizes for the three-way repeated-measures ANOVAs in Experiment 1.

11.
J Acoust Soc Am ; 146(1): 195, 2019 07.
Article in English | MEDLINE | ID: mdl-31370651

ABSTRACT

This study examined the contribution of perceptual and cognitive factors to speech-perception abilities in cochlear-implant (CI) users. Thirty CI users were tested on word intelligibility in sentences with and without semantic context, presented in quiet and in noise. Performance was compared with measures of spectral-ripple detection and discrimination, thought to reflect peripheral processing, as well as with cognitive measures of working memory and non-verbal intelligence. Thirty age-matched and thirty younger normal-hearing (NH) adults also participated, listening via tone-excited vocoders, adjusted to produce mean performance for speech in noise comparable to that of the CI group. Results suggest that CI users may rely more heavily on semantic context than younger or older NH listeners, and that non-auditory working memory explains significant variance in the CI and age-matched NH groups. Between-subject variability in spectral-ripple detection thresholds was similar across groups, despite the spectral resolution for all NH listeners being limited by the same vocoder, whereas speech perception scores were more variable between CI users than between NH listeners. The results highlight the potential importance of central factors in explaining individual differences in CI users and question the extent to which standard measures of spectral resolution in CIs reflect purely peripheral processing.


Subject(s)
Auditory Perception/physiology , Cognition/physiology , Memory, Short-Term/physiology , Speech Perception/physiology , Speech/physiology , Adult , Aged , Cochlear Implantation/methods , Cochlear Implants , Female , Hearing Tests/methods , Humans , Male , Middle Aged
12.
J Assoc Res Otolaryngol ; 20(2): 151-167, 2019 04.
Article in English | MEDLINE | ID: mdl-30456730

ABSTRACT

Poor spectral resolution contributes to the difficulties experienced by cochlear implant (CI) users when listening to speech in noise. However, correlations between measures of spectral resolution and speech perception in noise have not always been found to be robust. It may be that the relationship between spectral resolution and speech perception in noise becomes clearer in conditions where the speech and noise are not spectrally matched, so that improved spectral resolution can assist in separating the speech from the masker. To test this prediction, speech intelligibility was measured with noise or tone maskers that were presented either in the same spectral channels as the speech or in interleaved spectral channels. Spectral resolution was estimated via a spectral ripple discrimination task. Results from vocoder simulations in normal-hearing listeners showed increasing differences in speech intelligibility between spectrally overlapped and interleaved maskers as well as improved spectral ripple discrimination with increasing spectral resolution. However, no clear differences were observed in CI users between performance with spectrally interleaved and overlapped maskers, or between tone and noise maskers. The results suggest that spectral resolution in current CIs is too poor to take advantage of the spectral separation produced by spectrally interleaved speech and maskers. Overall, the spectrally interleaved and tonal maskers produce a much larger difference in performance between normal-hearing listeners and CI users than do traditional speech-in-noise measures, and thus provide a more sensitive test of speech perception abilities for current and future implantable devices.


Subject(s)
Cochlear Implants , Speech Perception , Aged , Female , Humans , Male , Middle Aged , Noise , Speech
14.
Am J Hum Biol ; 28(4): 545-54, 2016 07.
Article in English | MEDLINE | ID: mdl-26833705

ABSTRACT

OBJECTIVE: In the developmental programming literature, the association of birth weight and blood pressure later in life is modest at best. This article reexamines this issue using Covariate Density Defined mixture of regressions (CDDmr) to determine if a latent variable, based on birth weight, and known to influence infant mortality, provides a stronger indicator of developmental programming. METHODS: CDDmr identifies two latent components in the birth weight distribution, generally interpreted in the infant mortality literature as "compromised" and "normal" fetal development. The data are taken from the 1958 British National Child Development Study. RESULTS: In the 1958 cohort, the "compromised" component consists of about 10% of the birth weight distribution. Compared to "normal" births, the mean systolic blood pressure at age 45 of "compromised" births is 20.3 (females) and 26.4 (males) mm Hg higher than "normal" births. The relative risks of stage-I-II systolic hypertension (>140 mm Hg) of "compromised" births compared to "normal" births are 10.7 (females) and 4.2 (males). The relative risks of stage-II systolic hypertension (>160 mm Hg) are considerably higher, 241.6 (females) and 74.3 (males). In general, the highest blood pressures are observed in "compromised" births with birth weights within the normal (about 3.0-3.5 kg) birth weight range. Results for diastolic blood pressure are similar. CONCLUSIONS: These associations are much stronger than those identified using conventional methods. CDDmr is likely to be useful for studying the dynamics of developmental programming particularly in large cohort studies where birth weight is often the only indicator of programming available. Am. J. Hum. Biol. 28:545-554, 2016. © 2016 Wiley Periodicals, Inc.


Subject(s)
Birth Weight , Blood Pressure , Infant Mortality , Adult , Child , Child, Preschool , England , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Scotland , Sex Factors , Wales , Young Adult
15.
Clin Liver Dis ; 19(1): 99-121, 2015 Feb.
Article in English | MEDLINE | ID: mdl-25454299

ABSTRACT

Different imaging modalities including ultrasonography, computed tomography (CT), and MR imaging may be used in the liver depending on the clinical situation. The ability of dedicated contrast-enhanced liver MR imaging or CT to definitively characterize lesions as benign is crucial in avoiding unnecessary biopsy. Liver imaging surveillance in patients with cirrhosis may allow for detection of hepatocellular carcinoma at an earlier stage, and therefore may improve outcome. This article reviews the different imaging modalities used to evaluate the liver and focal benign and malignant hepatic lesions, and the basic surveillance strategy for patients at increased risk for hepatocellular carcinoma.


Subject(s)
Adenoma/diagnosis , Bile Duct Neoplasms/diagnosis , Carcinoma, Hepatocellular/diagnosis , Cholangiocarcinoma/diagnosis , Focal Nodular Hyperplasia/diagnosis , Hemangioma/diagnosis , Liver Neoplasms/diagnosis , Magnetic Resonance Imaging , Bile Ducts, Intrahepatic , Contrast Media , Cysts/diagnosis , Humans , Liver Neoplasms/secondary , Tomography Scanners, X-Ray Computed , Ultrasonography, Doppler, Color
16.
Radiol Clin North Am ; 52(4): 757-77, 2014 Jul.
Article in English | MEDLINE | ID: mdl-24889170

ABSTRACT

Magnetic resonance (MR) imaging of the pancreas is useful as both a problem-solving tool and an initial imaging examination of choice. With newer imaging sequences such as diffusion-weighted imaging, MR offers improved ability to detect and characterize lesions and identify and stage tumors and inflammation. MR cholangiopancreatography can be used to visualize the pancreatic and biliary ductal system. In this article, the use of MR to evaluate the pancreas, including recent advances, is reviewed and the normal appearance of the pancreas on different imaging sequences, as well as inflammatory diseases, congenital abnormalities, and neoplasms of the pancreas, are discussed.


Subject(s)
Magnetic Resonance Imaging/methods , Pancreas , Pancreatic Diseases/diagnosis , Artifacts , Cholangiopancreatography, Magnetic Resonance , Contrast Media , Diffusion Magnetic Resonance Imaging , Humans , Pancreas/abnormalities , Pancreas/anatomy & histology , Pancreas/pathology , Pancreatic Diseases/pathology
17.
Demography ; 50(2): 615-35, 2013 Apr.
Article in English | MEDLINE | ID: mdl-23073749

ABSTRACT

This research determines whether the observed decline in infant mortality with socioeconomic level, operationalized as maternal education (dichotomized as college or more, versus high school or less), is due to its "indirect" effect (operating through birth weight) and/or to its "direct" effect (independent of birth weight). The data used are the 2001 U.S. national African American, Mexican American, and European American birth cohorts by sex. The analysis explores the birth outcomes of infants undergoing normal and compromised fetal development separately by using covariate density defined mixture of logistic regressions (CDDmlr). Among normal births, mean birth weight increases significantly (by 27-108 g) with higher maternal education. Mortality declines significantly (by a factor of 0.40-0.96) through the direct effect of education. The indirect effect of education among normal births is small but significant in three cohorts. Furthermore, the indirect effect of maternal education tends to increase mortality despite improved birth weight. Among compromised births, education has small and inconsistent effects on birth weight and infant mortality. Overall, our results are consistent with the view that the decrease in infant death by socioeconomic level is not mediated by improved birth weight. Interventions targeting birth weight may not result in lower infant mortality.


Subject(s)
Birth Weight , Educational Status , Infant Mortality/trends , Mothers , Black or African American/statistics & numerical data , Female , Humans , Infant, Newborn , Logistic Models , Male , Mexican Americans/statistics & numerical data , Socioeconomic Factors , United States/epidemiology , White People/statistics & numerical data
18.
BMC Pregnancy Childbirth ; 10: 86, 2010 Dec 28.
Article in English | MEDLINE | ID: mdl-21189146

ABSTRACT

BACKGROUND: It has been hypothesized that birth weight is not on the causal pathway to infant mortality, at least among "normal" births (i.e. those located in the central part of the birth weight distribution), and that US racial disparities (African American versus European American) may be underestimated. Here these hypotheses are tested by examining the role of birth weight on racial disparities in infant mortality. METHODS: A two-component Covariate Density Defined mixture of logistic regressions model is used to decompose racial disparities, 1) into disparities due to "normal" versus "compromised" components of the birth cohort, and 2) further decompose these components into indirect effects, which are associated with birth weight, versus direct effects, which are independent of birth weight. RESULTS: The results indicate that a direct effect is responsible for the racial disparity in mortality among "normal" births. No indirect effect of birth weight is observed despite significant disparities in birth weight. Among "compromised" births, an indirect effect is responsible for the disparity, which is consistent with disparities in birth weight. However, there is also a direct effect among "compromised" births that reduces the racial disparity in mortality. This direct effect is responsible for the "pediatric paradox" and maybe due to differential fetal loss. Model-based adjustment for this effect indicates that racial disparities corrected for fetal loss could be as high as 3 or 4 fold. This estimate is higher than the observed racial disparities in infant mortality (2.1 for both sexes). CONCLUSIONS: The results support the hypothesis that birth weight is not on the causal pathway to infant mortality among "normal" births, although birth weight could play a role among "compromised" births. The overall size of the US racial disparities in infant mortality maybe considerably underestimated in the observed data possibly due to racial disparities in fetal loss.


Subject(s)
Birth Weight , Black or African American/statistics & numerical data , Health Status Disparities , Infant Mortality/ethnology , White People/statistics & numerical data , Female , Fetal Death/ethnology , Humans , Infant, Newborn , Logistic Models , Male , United States/epidemiology
20.
Am J Epidemiol ; 169(3): 294-303, 2009 Feb 01.
Article in English | MEDLINE | ID: mdl-19029004

ABSTRACT

It has been argued (e.g., the Wilcox-Russell hypothesis) that (low) birth weight is a correlate of adverse birth outcomes but is not on the "causal" pathway to infant mortality. However, the US national policy for reducing infant mortality is to reduce low birth weight. If these theoretical views are correct, lowering the rate of low birth weight may have little effect on infant mortality. In this paper, the authors use the "covariate density defined mixture of logistic regressions" method to formally test the Wilcox-Russell hypothesis that a covariate which influences birth weight, in this case maternal age, can influence infant mortality directly but not indirectly through birth weight. The authors analyze data from 8 populations in New York State (1985-1988). The results indicate that among the populations examined, 1) maternal age significantly influences the birth weight distribution and 2) maternal age also affects infant mortality directly, but 3) the influence of maternal age on the birth weight distribution has little or no effect on infant mortality, because the birth-weight-specific mortality curve shifts accordingly to compensate for changes in the birth weight distribution. These results tend to support the Wilcox-Russell hypothesis for maternal age.


Subject(s)
Infant Mortality/trends , Logistic Models , Maternal Age , Birth Weight , Female , Humans , Infant , Infant, Newborn , Male , New York/epidemiology , Parity , Pregnancy , Statistics, Nonparametric
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