Variation In Prevalence Estimates Research Articles

Prevalence of PTSD in Active Duty Members with Mild Traumatic Brain Injury: Systematic Review and Meta-analysis.

Traumatic brain injury (TBI), particularly mild TBI (mTBI), is a significant health concern for U.S. active duty service members (ADSMs), with potential implications for psychiatric outcomes including PTSD. Despite recognizing this association, the prevalence of PTSD among ADSMs with mTBI remains unclear. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A thorough search in PubMed, CINAHL, Embase, and PsycINFO databases from 2008 to 2024 focused on identifying studies involving ADSMs with PTSD and mTBI. The R software (version 4.3.2) was employed for meta-analysis with the "meta" and "meta prop" packages. Eight reviewed studies revealed a pooled prevalence estimate of PTSD among ADSMs with mTBI at 36% (95% CI, 30%-41%, P < .01, I2 = 96%). Cohort studies indicated a slightly higher prevalence of 38% (95% CI, 19%-59%, P < .01, I2 = 98%), whereas cross-sectional studies provided a marginally lower prevalence of 34% (95% CI, 27%-40%, P < .01, I2 = 92%). Methodological differences, including diagnostic criteria variability, contribute to the observed variability in prevalence estimates. Despite methodological challenges, this study provides crucial insights into the pooled prevalence of comorbid PTSD and mTBI within the military, emphasizing the need for standardized methodologies and further research to refine understanding and support strategies for affected individuals.

Trends estimation of obesity prevalence among South Asian young population: a systematic review and meta-analysis

The premise for effective prevention and treatment of obesity is the availability of accurate prevalence figures. However, the prevalence of pediatric obesity and overweight in South Asian countries has seldom been analyzed. This article provides a comprehensive review and meta-analysis of studies on overweight and obesity to provide a more precise prevalence estimate. The study protocol was registered on PROSPERO (CRD42022320625). PubMed and Embase databases were comprehensively searched from inception till September 2023. The random-effects model was utilized to derive the pooled prevalence of obesity and overweight. Subgroup meta-analysis was used to assess variations in prevalence estimates across subgroups. A meta-regression analysis was also performed to assess the trend of overweight and obesity over the years. 152 studies were included with 489,525 participants. The pooled prevalence was 12.4 (95% CI 11.1–13.6) for overweight, 6.6% (95% CI 5.6–7.8) for obesity, and 19.3% (95% CI 17.1–21.7) for obesity and overweight. In subgroup analysis, Bangladesh reported a higher prevalence for both obesity (8.9%; 95% CI 4.9–13.9) and overweight (13.6%; 95% CI 9.2–18.8). Meta-regression analysis found a significant association between obesity prevalence and the publication year (β = 0.004; p = 0.03; R2 = 2.74%). The results of this study indicate a relatively higher prevalence of childhood obesity in South Asia, emphasizing the necessity for large-scale awareness efforts and context-specific preventative methods.

Prevalence of Long-term Symptoms Varies When Using Different Post-COVID-19 Definitions in Positively and Negatively Tested Adults: The PRIME Post-COVID Study.

Long-term symptoms after a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (ie, post-coronavirus disease 2019 [COVID-19] condition or long COVID) constitute a substantial public health problem. Yet, the prevalence remains currently unclear as different case definitions are used, and negatively tested controls are lacking. We aimed to estimate post-COVID-19 condition prevalence using 6 definitions. The Prevalence, Risk factors, and Impact Evaluation (PRIME) post-COVID-19 condition study is a population-based sample of COVID-19-tested adults. In 2021, 61 655 adults were invited to complete an online questionnaire, including 44 symptoms plus a severity score (0-10) per symptom. Prevalence was calculated in both positively and negatively tested adults, stratified by time since their COVID-19 test (3-5, 6-11, or ≥12 months ago). In positive individuals (n = 7405, 75.6%), the prevalence of long-term symptoms was between 26.9% and 64.1% using the 6 definitions, while in negative individuals (n = 2392, 24.4%), the prevalence varied between 11.4% and 32.5%. The prevalence of long-term symptoms potentially attributable to COVID-19 ranged from 17.9% to 26.3%. There is a (substantial) variation in prevalence estimates when using different post-COVID-19 condition definitions, as is current practice; there is limited overlap between definitions, indicating that the essential post-COVID-19 condition criteria are still unclear. Including negatives is important to determine long-term symptoms attributable to COVID-19. ClinicalTrials.gov Identifier: NCT05128695.

Prevalence of five human pathogens in host-seeking Ixodes scapularis and Ixodes pacificus by region, state, and county in the contiguous United States generated through national tick surveillance

The majority of vector-borne disease cases reported in the United States (U.S.) are caused by pathogens spread by the blacklegged tick, Ixodes scapularis. In recent decades, the geographic ranges of the tick and its associated human pathogens have expanded, putting an increasing number of communities at risk for tick-borne infections. In 2018, the U.S. Centers for Disease Control and Prevention (CDC) initiated a national tick surveillance program to monitor changes in the distribution and abundance of ticks and the presence and prevalence of human pathogens in them. We assessed the geographical representativeness of prevalence data submitted to CDC as part of the national tick surveillance effort. We describe county, state, and regional variation in the prevalence of five human pathogens (Borrelia burgdorferi sensu stricto (s.s.), Borrelia mayonii, Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia microti) in host-seeking I. scapularis and I. pacificus nymphs and adults. Although I. scapularis and I. pacificus are widely distributed in the eastern and western U.S., respectively, pathogen prevalence was estimated predominantly in ticks collected in the Northeast, Ohio Valley, and Upper Midwest regions, where human Lyme disease cases are most commonly reported. Within these regions, we found that state and regional estimates of pathogen prevalence generally reached predictable and stable levels, but variation in prevalence estimates at the sub-state level was considerable. Borrelia burgdorferi s.s. was the most prevalent and widespread pathogen detected. Borrelia miyamotoi and A. phagocytophilum shared a similarly broad geographic range, but were consistently detected at much lower prevalence compared with B. burgdorferi s.s. Babesia microti was detected at similar prevalence to A. phagocytophilum, where both pathogens co-occurred, but was reported over a much more limited geographic range compared with A. phagocytophilum or B. burgdorferi s.s. Borrelia mayonii was identified at very low prevalence with a focal distribution within the Upper Midwest. National assessments of risk for tick-borne diseases need to be improved through collection and testing of ticks in currently under-represented regions, including the West, South, Southeast, and eastern Plains states.

Prevalence of Autism Spectrum Disorder in the Centro region of Portugal: a population based study of school age children within the ASDEU project.

Accurate prevalence estimates for Autism Spectrum Disorder (ASD) are fundamental to adequately program medical and educational resources for children. However, estimates vary globally and across Europe, and it is therefore wise to conduct epidemiological studies in defined geo-cultural contexts. We used a population screening approach to estimate the prevalence of ASD in the Centro region of Portugal, using a harmonized protocol as part of the Autism Spectrum Disorders in the European Union (ASDEU) project. The overall prevalence was estimated at 0.5% (95% CI 0.3-0.7), higher in schools with Autism Units (3.3%, 95%CI 2.7-3.9) than in regular schools (0.3%, 95% CI 0.1-0.5) or schools with Multiple Disability Units (0.3%, 95% CI 0.04-0.6). The results indicate that the diagnosis of ASD is followed by the most effective educational policies in Centro Region. The variability in prevalence estimates across the different regions from the ASDEU project, and globally, is discussed.

P23 Prevalence of asymptomatic bacteriuria and associated risk factors in an adult population relevant to UK primary care: a systematic review and meta-analysis

Abstract Background The use of urine dipstick tests in people who are more likely to have asymptomatic bacteriuria (ASB) can lead to the over-diagnosis of urinary tract infection (UTI) and unnecessary antibiotic prescribing. As a result, urine dipsticks are not recommended in those over the age of 65 years, or those with a urinary catheter in UK primary care guidelines. However, due to variation in prevalence estimates for ASB and the age of some of the existing prevalence studies it is unclear whether the use of age 65 as a cut-off for dipstick testing remains appropriate. Objectives This systematic review aims to identify and synthesize more recent evidence around ASB prevalence and other risk factors relevant to a UK community context, in order to improve how UK primary care UTI diagnostic guidance addresses asymptomatic bacteriuria. Methods The protocol for this systematic review is registered with PROSPERO. Inclusion criteria are: study participants aged ≥18 years; prospective studies recruiting from a primary care relevant population; studies that measure ASB prevalence and risk factors; and studies from the Organization for Economic Co-operation and Development member countries. Exclusion criteria include: studies from inpatient hospital settings (including the emergency department); studies exclusively including people who are pregnant, who have urinary catheters, who are post renal transplant or who have structural urological abnormalities; animal studies; laboratory studies; studies published before 1990; and studies not written in English. Searches were conducted in CINAHL, Embase and Medline using MeSH and free text words adapted for each database including terms for bacteriuria AND asymptomatic disease. The Cochrane Collaboration Covidence platform is being used for the management of screening and assessment of studies. Two authors are independently completing screening, data extraction and quality assessments. Results The initial search identified 3891 studies. After screening, 685 are currently undergoing full text review. Overall findings will be reported in a narrative synthesis. We will describe the studies identified, including how ASB has been defined within each of the studies. If sufficient data are available we will complete a meta-analysis. Using standard meta-analysis methods we will generate forest plots showing prevalence and 95% CIs for each study. If possible, we will estimate pooled prevalence of ASB from the reported prevalence of eligible studies, by age group and gender. Conclusions The results of this review may highlight where new evidence around ASB prevalence and risk factors relevant to a UK primary care population is needed.

Undernutrition among children living in refugee camps: a systematic review of prevalence

ObjectivesThis review aimed to provide an overview of the prevalence of undernutrition in children under 5 years old in refugee camps according to the different indicators. In addition, we aimed...

Evaluation of Respondent-Driven Sampling Prevalence Estimators Using Real-World Reported Network Degree.

Respondent-driven sampling (RDS) is used to measure trait or disease prevalence in populations that are difficult to reach and often marginalized. The authors evaluated the performance of RDS estimators under varying conditions of trait prevalence, homophily, and relative activity. They used large simulated networks (N = 20,000) derived from real-world RDS degree reports and an empirical Facebook network (N = 22,470) to evaluate estimators of binary and categorical trait prevalence. Variability in prevalence estimates is higher when network degree is drawn from real-world samples than from the commonly assumed Poisson distribution, resulting in lower coverage rates. Newer estimators perform well when the sample is a substantive proportion of the population, but bias is present when the population size is unknown. The choice of preferred RDS estimator needs to be study specific, considering both statistical properties and knowledge of the population under study.

The impact of varying the number and selection of conditions on estimated multimorbidity prevalence: A cross-sectional study using a large, primary care population dataset.

Multimorbidity prevalence rates vary considerably depending on the conditions considered in the morbidity count, but there is no standardised approach to the number or selection of conditions to include. We conducted a cross-sectional study using English primary care data for 1,168,260 participants who were all people alive and permanently registered with 149 included general practices. Outcome measures of the study were prevalence estimates of multimorbidity (defined as ≥2 conditions) when varying the number and selection of conditions considered for 80 conditions. Included conditions featured in ≥1 of the 9 published lists of conditions examined in the study and/or phenotyping algorithms in the Health Data Research UK (HDR-UK) Phenotype Library. First, multimorbidity prevalence was calculated when considering the individually most common 2 conditions, 3 conditions, etc., up to 80 conditions. Second, prevalence was calculated using 9 condition-lists from published studies. Analyses were stratified by dependent variables age, socioeconomic position, and sex. Prevalence when only the 2 commonest conditions were considered was 4.6% (95% CI [4.6, 4.6] p < 0.001), rising to 29.5% (95% CI [29.5, 29.6] p < 0.001) considering the 10 commonest, 35.2% (95% CI [35.1, 35.3] p < 0.001) considering the 20 commonest, and 40.5% (95% CI [40.4, 40.6] p < 0.001) when considering all 80 conditions. The threshold number of conditions at which multimorbidity prevalence was >99% of that measured when considering all 80 conditions was 52 for the whole population but was lower in older people (29 in >80 years) and higher in younger people (71 in 0- to 9-year-olds). Nine published condition-lists were examined; these were either recommended for measuring multimorbidity, used in previous highly cited studies of multimorbidity prevalence, or widely applied measures of "comorbidity." Multimorbidity prevalence using these lists varied from 11.1% to 36.4%. A limitation of the study is that conditions were not always replicated using the same ascertainment rules as previous studies to improve comparability across condition-lists, but this highlights further variability in prevalence estimates across studies. In this study, we observed that varying the number and selection of conditions results in very large differences in multimorbidity prevalence, and different numbers of conditions are needed to reach ceiling rates of multimorbidity prevalence in certain groups of people. These findings imply that there is a need for a standardised approach to defining multimorbidity, and to facilitate this, researchers can use existing condition-lists associated with highest multimorbidity prevalence.

Sources of variation in estimates of Duchenne and Becker muscular dystrophy prevalence in the United States

BackgroundDirect estimates of rare disease prevalence from public health surveillance may only be available in a few catchment areas. Understanding variation among observed prevalence can inform estimates of prevalence in other locations. The Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) conducts population-based surveillance of major muscular dystrophies in selected areas of the United States. We identified sources of variation in prevalence estimates of Duchenne and Becker muscular dystrophy (DBMD) within MD STARnet from published literature and a survey of MD STARnet investigators, then developed a logic model of the relationships between the sources of variation and estimated prevalence.ResultsThe 17 identified sources of variability fell into four categories: (1) inherent in surveillance systems, (2) particular to rare diseases, (3) particular to medical-records-based surveillance, and (4) resulting from extrapolation. For the sources of uncertainty measured by MD STARnet, we estimated each source’s contribution to the total variance in DBMD prevalence. Based on the logic model we fit a multivariable Poisson regression model to 96 age–site–race/ethnicity strata. Age accounted for 74% of the variation between strata, surveillance site for 6%, race/ethnicity for 3%, and 17% remained unexplained.ConclusionVariation in estimates derived from a non-random sample of states or counties may not be explained by demographic differences alone. Applying these estimates to other populations requires caution.

Use of psychotropic medications in adults with intellectual disability: A systematic review and meta-analysis.

This study presents the proportion of adults with intellectual disability using psychotropic medications including antipsychotics, antidepressants, anxiolytics, hypnotics and sedatives, and psychostimulants. A search was performed in PubMed, Embase, PsycINFO, Web of Science, and Scopus up to 31 December 2021. Articles were included if they reported the proportion of adults with intellectual disability using psychotropic medications. Frequency of use was estimated using a random effects meta-analysis. Meta-regression analysis was used to assess the association between study-level characteristics and variability in estimates, when heterogeneity was considerable. Twenty-four articles were included in pooled analysis. The pooled prevalence of psychotropic medications was 41% (95% confidence interval: 35-46%). Pooled prevalences of subclasses were as follows: antipsychotics 31% (27-35%), antidepressants 14% (9-19%), anxiolytics 9% (4-15%), hypnotics/sedatives 5% (2-8%), and psychostimulants 1% (1-2%). Heterogeneity was considerable between studies, except for psychostimulants. There was no significant association between assessed characteristics and variability in prevalence estimates. Two-fifths of adults with intellectual disability were prescribed psychotropic medications. Antipsychotics and antidepressants were used by one-third and one-seventh of adults, respectively. There was considerable variability between studies, and further investigation is required to determine the source of variability. More studies are needed to better characterise prescribed psychotropic medications, including effectiveness and adverse effects, to ensure appropriate use of these drugs.

County-level prevalence estimates of ADHD in children in the United States

PurposeAttention-deficit/hyperactivity disorder (ADHD) is a common childhood disorder often characterized by long-term impairments in family, academic, and social settings. Measuring the prevalence of ADHD is important as treatment options increase around the U.S. Prevalence data helps inform decisions by care providers, policymakers, and public health officials about allocating resources for ADHD. In addition, measuring geographic variation in prevalence estimates can facilitate hypothesis generation for future analytic work. Most U.S. studies of ADHD prevalence among children focus on national or demographic group rates. MethodsUsing a small area estimation approach and data from the 2016 to 2018 National Survey of Children's Health, we estimated childhood ADHD prevalence estimates at the census regional division, state, and county levels. The sample included approximately 70,000 children aged 5–17 years. ResultsThe national ADHD rate was estimated to be 12.9% (95% Confidence Interval: 11.5%, 14.4%). Counties in the West South Central, East South Central, New England, and South Atlantic divisions had higher estimated rates of childhood ADHD (55.1%, 53.6%, 49.3%, and 46.2% of the counties had rates of 16% or greater, respectively) compared to counties in the Mountain, Mid Atlantic, West North Central, Pacific, and East North Central divisions (2.1%, 4%, 5.8%, 6.9%, and 11.7% of the counties had rates of 16% or greater, respectively). ConclusionsThese local-level rates are useful for decision-makers to target programs and direct sufficient ADHD resources based on communities’ needs.

The influence of periodontitis case definition on the association between periodontal disease and glycaemic status.

The association between periodontitis and glycaemic control is complex, and often described as 'bidirectional'. Although epidemiological studies have examined this relationship extensively, a disagreement on periodontitis case definition still exists. This study aimed to assess the influence of case definition on the association between periodontal disease and glycaemic status. The study is a secondary analysis of data from the United States National Health and Nutrition Examination Survey (NHANES), 2009-2014 cycles. The association between periodontitis and glycated haemoglobin (HbA1c) was assessed using different periodontitis case definitions: the definition by the Centers for Disease Control and Prevention and the American Academy of Periodontology (CDC/AAP), Community Periodontal Index (CPI), ≥1 site with ≥3 mm clinical attachment loss (CAL) and ≥4 mm probing depth (PD), ≥1 site with ≥4 mm CAL and ≥4 mm PD, the 5th European Workshop definitions, Machtei et al. 'established periodontitis', the 2017 World Workshop classification, and self-reported periodontitis. The associations between periodontitis and HbA1c were compared across the case definitions. There was substantial variability in prevalence estimates of periodontitis, and in the strength of association between periodontitis and HbA1c when different case definitions were applied. The CDC/AAP and stage III/IV periodontitis were consistently significantly associated with elevated HbA1c. For stage III/IV, the adjusted odds ratios of prediabetes and diabetes HbA1c were 1.19 and 1.76, respectively. Comprehensive periodontitis case definitions that account for CAL and PD, such as the CDC/AAP and the 2017 classification, seem to better detect the association between periodontal disease and HbA1c.

Polycystic ovarian syndrome among women diagnosed with infertility in the Gulf Cooperation Council countries: A protocol for systematic review and meta-analysis of prevalence studies.

Polycystic ovarian syndrome, a common endocrine disorder, is an important cause of infertility among women of reproductive age. Within the Gulf Cooperation Council countries, polycystic ovarian syndrome is found to affect women increasingly. No study has been carried out to critically summarize the evidence on the prevalence of polycystic ovarian syndrome among women suffering from infertility in these countries. This protocol aims to conduct a systematic review and meta-analysis of the studies reporting the prevalence of polycystic ovarian syndrome among women seeking infertility treatment in the six Gulf Cooperation Council countries (Bahrain, Kuwait, Oman, Saudi Arabia, Qatar, and United Arab Emirates). The systematic review and meta-analysis will follow the following method. Five databases, including PubMed, Embase, CINAHL, Web of Science, and SCOPUS, will be searched for observational studies using a combination of relevant keywords and Medical Subject Headings from inception of databases. Two reviewers will screen titles and abstracts, followed by a full-text search based on the eligibility criteria. The main outcome is to measure the proportion of women who have polycystic ovarian syndrome among infertility-diagnosed patients. In addition, the risk of bias in the included studies will be assessed using the national institute of health quality assessment tool for observational studies. The random-effects method of the analysis with the inverse variance will be used to calculate the pooled prevalence of polycystic ovarian syndrome-attributed infertility. Variation in prevalence estimates will be calculated using subgroup analysis based on study and patients' characteristics and publication bias will be assessed via funnel plot inspection and Eggar's test. A critical assessment of evidence on the prevalence of polycystic ovarian syndrome in women attending fertility clinics is helpful in risk quantification, enabling better planning for managing infertility in women with polycystic ovarian syndrome. This protocol has been registered with PROSPERO, protocol registration number (CRD42022355087).

Seroprevalence of Toxoplasma gondii infection in sheep and goats from different geographical regions of the world: Systematic review and meta-analysis.

The Toxoplasma gondii is an obligate intracellular protozoan parasite which significantly impact small ruminant productivity, international animal trade and transboundary movement of animal across the globe. The seroprevalence of T. gondii infection (toxoplasmosis) in sheep and goats is widely studied in many parts of the world and there is a lack of comprehensive information on prevalence estimates considering the global and regional perspectives. The aim of the study was to use systematic review and meta-analysis methods to estimate the global and regional pooled seroprevalence of T. gondii infection in sheep and goats, as well as factors that influence prevalence estimations. Relevant articles reporting the seroprevalence of toxoplasmosis in sheep and/goats were searched in five electronic databases, including PubMed, Web of Science, Scopus, Embase and ProQuest. After the publications were checked to verify they fit the inclusion criteria, a total of 225 articles were included in the systematic review and meta-analysis, reflecting data from 70 countries/regions. The pooled prevalence was estimated using a random effect meta-analysis model. Overall, the seroprevalence of T. gondii infection was 33.86% (95% CI: 30.47-37.25%) in sheep and 31.78% (95% CI: 28.99-34.58%) in goats, with significant variation in prevalence estimates across geographical locations (p<.001). Substantial heterogeneity (I2 >75%) was observed in most pooled seroprevalence estimates. The T. gondii infection in global sheep and goat population showed uptrend over the period. This information would be useful for epidemiologist, health authorities and farmers in order to plan future T. gondii survey and infection management strategies both locally and internationally.

Prevalence of medically unexplained symptoms in adults who are high users of healthcare services and magnitude of associated costs: a systematic review

IntroductionMedically unexplained symptoms (MUS) is a common clinical syndrome in primary and secondary healthcare service. Outcomes for patients with persistent MUS include increased disability, poorer quality of life and higher...

Does the definition of preventable emergency department visit matter? An empirical analysis using 20 million visits in Ontario and Alberta.

This study had two objectives: (1) to estimate the prevalence of preventable emergency department (ED) visits during the 2016-2020 time period among those living in 19 large urban centers in Alberta and Ontario, Canada, and (2) to assess if the definition of preventable ED visits matters in estimating the prevalence. A retrospective, population-based study of ED visits that were reported to the National Ambulatory Care Reporting System from April 1, 2016, to March 31, 2020, was conducted. Preventable ED visits were operationalized based on the following approaches: (1) Canadian Triage and Acuity Scale (CTAS), (2) ambulatory care-sensitive conditions (ACSC), (3) family practice-sensitive conditions (FPSC), and (4) sentinel nonurgent conditions (SNC). The overall proportion of ED visits that were preventable was estimated. We also estimated the adjusted relative risks of preventable ED visits by patients' sex and age, fiscal year, province of residence, and census metropolitan area (CMA) of residence. There were 20,171,319 ED visits made by 8,919,618 patients ages 1 to 74 who resided in one of the 19 CMAs in Alberta or Ontario. On average, there were 2.26 visits per patient over the period of 4 fiscal years; most patients made one (44.22%) or two ED visits (20.72%). The overall unadjusted prevalence of preventable ED visits varied by definition; 35.33% of ED visits were defined as preventable based on CTAS, 12.88% based on FPSC, 3.41% based on SNC, and 2.33% based on ACSC. There is a substantial level of variation in prevalence estimates across definitions of preventable ED visits, and care should be taken when interpreting these estimates as each has a different meaning and may lead to different conclusions. The conceptualization and measurement of preventable ED visits is complex and multifaceted and may not be adequately captured by a single definition.

Trajectories of Dyspareunia From Pregnancy to 24 Months Postpartum

(Abstracted from Obstet Gynecol 2022;139(3):391–399) Dyspareunia, defined as pain during vaginal intercourse, commonly affects women during pregnancy and the postpartum period. Although its prevalence has been extensively studied, the wide variability in prevalence estimates may be explained by heterogeneity in trajectories of dyspareunia, which have not been established.

Prevalence of alcohol and other drug use in patients presenting to hospital for fall-related injuries: a systematic review

BackgroundAlcohol and other drug (AOD) use is a key preventable risk factor for serious injuries. Prevention strategies to date have largely focused on transport injuries, despite AOD use being a...

Ways Forward in Preventing Severe Maternal Morbidity and Maternal Health Inequities: Conceptual Frameworks, Definitions, and Data, from a Population Health Perspective.

Ways Forward in Preventing Severe Maternal Morbidity and Maternal Health Inequities: Conceptual Frameworks, Definitions, and Data, from a Population Health Perspective.