Case/control studies with follow-up: Constructing the source population to estimate effects of risk factors on development, disease, and survival

Oral hygiene, mouthwash usage and cardiovascular mortality during 18.8 years of follow-up

Aim(s) We tested the following hypotheses: would better oral hygiene self-care (OHS) influence cardiovascular (CVD) mortality? Will using mouthwash in addition to OHS affect CVD mortality? How does mouthwash usage impact the oral microbes?Design and methods Among 354 dentate subjects from the Kuopio Oral Health and Heart study, the association of OHS with CVD mortality was assessed using Cox regression analyses, adjusting for age, sex, smoking, dyslipidemia, diabetes, hypertension and education. Additionally, whether using mouthwash would affect this relationship was evaluated.Results In the multivariable-adjusted models, OHS was associated with a 51% reduction in the risk of CVD mortality (hazard ratio [HR] 0.49 [0.28-0.85]; p = 0.01). Even those who had coronary artery disease at baseline showed a marginally significant benefit (0.50 [0.24-1.06]; p = 0.07). However, mouthwash usage did not change OHS effects (HR = 0.49 [0.27-0.87]; p = 0.01), indicating no additional benefits nor detriments. All tested microbes trended to decrease with mouthwash usage in the short term, but none were statistically significant.Conclusion Good OHS significantly lowered the risk of CVD mortality relative to poor OHS. Mouthwash usage did not show any long-term harm or benefit on CVD mortality beyond the benefits rendered by brushing and flossing.

A comparison of risk factors for cryptosporidiosis and non-cryptosporidiosis diarrhoea: A case-case-control study in Ethiopian children

Background

Cryptosporidiosis is a major cause of diarrhoea in young children in low-and-middle-income countries. New interventions should be informed by evidence pertaining to risk factors and their relative importance. Inconsistencies in the literature may to some extent be explained by choice of methodology, furthermore, most previous risk factor studies compared cryptosporidiosis cases to diarrhoea cases of other aetiologies rather than with controls without diarrhoea.

Methodology/Principal findings

We investigated a broad set of factors in under-2-year-olds presenting with diarrhoea to a hospital and a health center in southwestern Ethiopia. We applied quantitative cut-offs to distinguish between cryptosporidiosis and incidental Cryptosporidium infection or carriage, a hierarchical causal framework to minimize confounding and overadjustment, and a case-case-control design, to describe risk factors for both cryptosporidiosis and non-cryptosporidiosis diarrhoea. Moderate and severe acute malnutrition were strongly associated with both cryptosporidiosis and non-cryptosporidiosis diarrhoea. Previous healthcare attendance and low maternal education were only associated with cryptosporidiosis, whereas unsafe child stool disposal, prematurity and early cessation of exclusive breastfeeding were significantly associated with non-cryptosporidiosis diarrhoea only. By estimation of population attributable fractions, socioeconomic factors—specifically low maternal education—and public tap water use, were apparently more important risk factors for cryptosporidiosis than for non-cryptosporidiosis diarrhoea.

Conclusions/Significance

Nutritional management of moderate acute malnutrition may be an effective intervention against cryptosporidiosis, particularly if combined with targeted therapy for cryptosporidiosis which, again, may mitigate nutritional insult. Focused caregiver education in healthcare settings and follow-up of children with acute malnutrition may prevent or improve outcomes of future episodes of cryptosporidiosis.

Antenatal Uterotonics as a Risk Factor for Intrapartum Stillbirth and First-day Death in Haryana, India: A Nested Case-control Study

BACKGROUND

Use of uterotonics like oxytocin to induce or augment labor has been shown to reduce placental perfusion and oxygen supply to the fetus, and studies indicate that it may increase the risk of stillbirth and neonatal asphyxia. Antenatal use of uterotonics, even without the required fetal monitoring and prompt access to cesarean section, is widespread, yet no study has adequately estimated the risk of intrapartum stillbirth and early neonatal deaths ascribed to such use. We conducted a case-control study to estimate this risk.

METHODS

We conducted a population-based case-control study nested in a cluster-randomized trial. From 2008 to 2010, we followed pregnant women in rural Haryana, India, monthly until delivery. We visited all live-born infants on day 29 to ascertain whether they were alive. We conducted verbal autopsies for stillbirths and neonatal deaths. Cases (n = 2,076) were the intrapartum stillbirths and day-1 deaths (early deaths), and controls (n = 532) were live-born babies who died between day 8 and 28 (late deaths).

RESULTS

Antenatal administration of uterotonics preceded 74% of early and 62% of late deaths, translating to an adjusted odds ratio (95% confidence interval [CI]) for early deaths of 1.7 (95% CI = 1.4, 2.1), and a population attributable risk of 31% (95% CI = 22%, 38%).

CONCLUSIONS

Antenatal administration of uterotonics was associated with a substantially increased risk of intrapartum stillbirth and day-1 death. See video abstract: http://links.lww.com/EDE/B707.

Pathogen-specific risk of seizure in children with moderate-to-severe diarrhoea: Case control study with follow-up

OBJECTIVE

To determine the pathogen-specific risk of seizure in under-five children hospitalised with moderate-to-severe diarrhoea (MSD) in rural settings.

METHOD

This was a prospective case-control study with follow-up, conducted in a sentinel facility of Global Enteric Multicenter Study in Mirzapur, a rural community of Bangladesh between 2007 and 2010. Children aged 0-59 months who presented with MSD and seizure constituted the cases whereas those who did not have seizure comprised the controls. MSD was defined if the episodes were associated with dehydration or dysentery or required hospitalisation with diarrhoea or dysentery. All enrolled children were followed up at home within 50-90 days of enrolment. A total of 64 cases and 128 randomly selected controls formed the analysable dataset.

RESULTS

The result of logistic regression analysis after adjusting for potential confounders revealed that shigellosis (Shigella species, OR = 5.34, 95% CI = 2.37-12.04) particularly S. flexneri (OR = 3.34, 95% CI = 1.48-7.57), S. flexneri 6 (OR = 23.24, 95% CI = 2.79-193.85), S. sonnei (OR = 6.90, 95% CI = 2.34-19.85); norovirus (OR = 6.77, 95% CI = 1.69-27.11), fever (OR = 16.75, 95% CI = 1.81-154.70) and loss of consciousness (OR = 35.25, 95% CI = 1.71-726.20) were the independent risk factors for seizure in MSD children. At enrolment, cases had lower WHZ (P = 0.006) compared to their peers, follow-up anthropometrics showed significant improvement in WHZ (P < 0.001) and WAZ (P < 0.05), whereas deterioration in HAZ (P < 0.001) in both cases and controls.

CONCLUSION

Childhood MSD episodes particularly due to Shigella and norovirus are often associated with seizure. Prompt identification and appropriate management of children with shigellosis may reduce occurrence and adverse consequences of seizure linked with MSD.

Risk factors for death among children 0-59 months of age with moderate-to-severe diarrhea in Manhiça district, southern Mozambique

Background

Despite major improvements in child survival rates, the number of deaths due to diarrhea remains unacceptably high. We aimed to describe diarrhea-associated mortality and evaluate risk factors for death among Mozambican children with moderate-to-severe diarrhea (MSD).

Methods

Between December 2007 and November 2012, children under-five with MSD were enrolled in Manhiça district, as part of the Global Enteric Multicenter study (GEMS). Clinical, epidemiological, and socio-demographic characteristics were collected. Anthropometric measurements were performed and stool samples collected upon recruitment. A follow-up visit ~ 60 days post-enrolment was conducted and verbal autopsies performed in all death cases.

Results

Of the 916 MSD-cases analyzed; 90% (821/916) completed 60 days follow-up and 69 patients died. The case fatality rate at follow-up was 8% (69/821), and the mortality rate 10.2 (95%CI: 7.75–13.59) deaths per 1000 persons-week at risk. Nearly half of the deaths 48% (33/69) among study participants clustered within 2 weeks of the onset of diarrhea.

Typical enteropathogenic Escherichia coli (typical EPEC) and Cryptosporidium were the two pathogens associated to an increased risk of death in the univariate analysis with (HR = 4.16, p = 0.0461) and (H = 2.84, p = 0.0001) respectively. Conversely, Rotavirus infection was associated to a decreased risk of death (HR = 0.52, p = 0.0198).

According to the multivariate analysis, risk factors for death included co-morbidities such as malnutrition (HR = 4.13, p <  0.0001), pneumonia/lower respiratory infection (HR = 3.51, p <  0.0001) or invasive bacterial disease (IBD) (HR = 6.80, p = 0.0009), presenting on arrival with lethargy or overt unconsciousness (HR = 1.73, p = 0.0302) or wrinkled skin (HR = 1.71, p = 0.0393), and cryptosporidium infection (HR = 2.14, p = 0.0038).

When restricting the analysis to those with available HIV results (n = 191, 22% of the total study sample), HIV was shown to be a significant risk factor for death (HR = 5.05, p = 0.0009).

Verbal autopsies were conducted in 100% of study deaths, and highlighted diarrhea as the main underlying cause of death 39%, (27/69); followed by HIV/AIDS related deaths 29.0% (20/69) and sepsis 11.6% (8/69).

Conclusion

Preventive strategies targeting Cryptosporidium, malnutrition and early identification and treatment of associated co-morbidities could contribute to the prevention of the majority of diarrhea associated deaths in Mozambican children.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3948-9) contains supplementary material, which is available to authorized users.

Caregiver responses and association with delayed care-seeking in children with uncomplicated and severe malaria

Background

Gaps remain in understanding the role of caregiver responses on time to seek appropriate care. The objective of this study was to describe caregiver responses to illness and the impact of these responses on time to seek appropriate care among children with malaria.

Methods

A case–control study of 325 children with severe (cases) and 325 children with uncomplicated (controls) malaria was conducted in Jinja, Uganda. Caregivers’ responses to their children’s illnesses and time to seek appropriate care were documented. Responses included staying at home, seeking care at drug shops, and seeking care at public health facilities classified into two types: (1) health facilities where caregiver initially sought care before enrollment, and (2) health facilities where children were provided appropriate care and enrolled in the study. Weighted Cox regression was used to determine risk factors for delays in time to seek appropriate care within 24 h of illness onset.

Results

Children staying home on self-medication was the most common initial response to illness among caregivers of controls (57.5%) and cases (42.4%, p < 0.001), followed by staying at home without medication (25.2%) and seeking care at drug shops (32.0%) for caregivers of controls and cases, respectively. Seeking care at drug shops was more common among caregivers of cases than of controls (32.0% vs. 12.3%; p < 0.001). However, compared to public health facilities, drug shops offered sub-optimal services with children less likely to have been examined (50.0% vs. 82.9%; p < 0.001) or referred to another facility (12.5% vs. 61.4%; p < 0.001). Upon adjustment for known risk factors for delay, initially seeking care at a drug shop (HR 0.37, p = 0.036) was associated with delay in seeking care at a health facility where appropriate care was provided. In contrast, those initially seeking care at public health facility before enrollment were more likely to subsequently seek care at another public health facility where appropriate care was provided (HR 5.55, p < 0.001).

Conclusion

Caregivers should be educated on the importance of promptly seeking care at a health facility where appropriate care can be provided. The role of drug shops in providing appropriate care to children with malaria needs to be reviewed.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2630-9) contains supplementary material, which is available to authorized users.

Estimating excess length of stay due to healthcare-associated infections: a systematic review and meta-analysis of statistical methodology

BACKGROUND

Healthcare-associated infection (HCAI) affects millions of patients worldwide. HCAI is associated with increased healthcare costs, owing primarily to increased hospital length of stay (LOS) but calculating these costs is complicated due to time-dependent bias. Accurate estimation of excess LOS due to HCAI is essential to ensure that we invest in cost-effective infection prevention and control (IPC) measures.

AIM

To identify and review the main statistical methods that have been employed to estimate differential LOS between patients with, and without, HCAI; to highlight and discuss potential biases of all statistical approaches.

METHODS

A systematic review from 1997 to April 2017 was conducted in PubMed, CINAHL, ProQuest and EconLit databases. Studies were quality-assessed using an adapted Newcastle-Ottawa Scale (NOS). Methods were categorized as time-fixed or time-varying, with the former exhibiting time-dependent bias. Two examples of meta-analysis were used to illustrate how estimates of excess LOS differ between different studies.

FINDINGS

Ninety-two studies with estimates on excess LOS were identified. The majority of articles employed time-fixed methods (75%). Studies using time-varying methods are of higher quality according to NOS. Studies using time-fixed methods overestimate additional LOS attributable to HCAI. Undertaking meta-analysis is challenging due to a variety of study designs and reporting styles. Study differences are further magnified by heterogeneous populations, case definitions, causative organisms, and susceptibilities.

CONCLUSION

Methodologies have evolved over the last 20 years but there is still a significant body of evidence reliant upon time-fixed methods. Robust estimates are required to inform investment in cost-effective IPC interventions.

Demographic, Socioeconomic, and Geographic Factors Leading to Severe Malaria and Delayed Care Seeking in Ugandan Children: A Case-Control Study

We studied associations between delayed care seeking, demographic, socioeconomic, and geographic factors and likelihood of severe malaria in Ugandan children. The study was based at Jinja Hospital, Uganda. We enrolled 325 severe malaria cases and 325 uncomplicated malaria controls matched by age and residence. Patient details, an itinerary of events in response to illness, household information, and location of participants' residences were captured. Conditional logistic regression was used to determine risk factors for severe malaria and delayed care seeking. Delayed care seeking (≥ 24 hours after fever onset; odds ratio [OR] 5.50; 95% confidence interval [CI] 2.70, 11.1), seeking care at a drug shop as the initial response to illness (OR 3.62; 95% CI 1.86, 7.03), and increasing distance from place of residence to the nearest health center (OR 1.45; 95% CI 1.17, 1.79) were independent risk factors for severe malaria. On subgroup analysis, delayed care seeking was a significant risk factor in children with severe malaria attributable to severe anemia (OR 15.6; 95% CI 3.02, 80.6), but not unconsciousness (OR 1.13; 95% CI 0.30, 4.28). Seeking care at a drug shop (OR 2.84; 95% CI 1.12, 7.21) and increasing distance to the nearest health center (OR 1.18; 95% CI 1.01, 1.37) were independent risk factors for delayed care seeking. Delayed care seeking and seeking care at a drug shop were risk factors for severe malaria. Seeking care at a drug shop was also a predictor of delayed care seeking. The role of drug shops in contributing to delayed care and risk of severe malaria requires further study.

The MAL-ED study: a multinational and multidisciplinary approach to understand the relationship between enteric pathogens, malnutrition, gut physiology, physical growth, cognitive development, and immune responses in infants and children up to 2 years of age in resource-poor environments

Highly prevalent conditions with multiple and complex underlying etiologies are a challenge to public health. Undernutrition, for example, affects 20% of children in the developing world. The cause and consequence of poor nutrition are multifaceted. Undernutrition has been associated with half of all deaths worldwide in children aged <5 years; in addition, its pernicious long-term effects in early childhood have been associated with cognitive and physical growth deficits across multiple generations and have been thought to suppress immunity to further infections and to reduce the efficacy of childhood vaccines. The Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health (MAL-ED) Study, led by the Fogarty International Center of the National Institutes of Health and the Foundation for the National Institutes of Health, has been established at sites in 8 countries with historically high incidence of diarrheal disease and undernutrition. Central to the study is the hypothesis that enteropathogen infection contributes to undernutrition by causing intestinal inflammation and/or by altering intestinal barrier and absorptive function. It is further postulated that this leads to growth faltering and deficits in cognitive development. The effects of repeated enteric infection and undernutrition on the immune response to childhood vaccines is also being examined in the study. MAL-ED uses a prospective longitudinal design that offers a unique opportunity to directly address a complex system of exposures and health outcomes in the community-rather than the relatively rarer circumstances that lead to hospitalization-during the critical period of development of the first 2 years of life. Among the factors being evaluated are enteric infections (with or without diarrhea) and other illness indicators, micronutrient levels, diet, socioeconomic status, gut function, and the environment. MAL-ED aims to describe these factors, their interrelationships, and their overall impact on health outcomes in unprecedented detail, and to make individual, site-specific, and generalized recommendations regarding the nature and timing of possible interventions aimed at improving child health and development in these resource-poor settings.

Number of teeth, C-reactive protein, fibrinogen and cardiovascular mortality: a 15-year follow-up study in a Finnish cohort

AIM

To test whether the number of teeth, an inverse proxy for composite oral infection scores is associated with better survival.

MATERIALS AND METHODS

The Kuopio Oral Health and Heart study initiated a case-control study in 1995-1996 consisting of 256 consecutive coronary artery disease patients and 250 age and gender-matched controls. We appended the mortality data and formulated a longitudinal study. By May 31st, 2011, 124 mortalities had occurred and 80 of which were of cardiovascular origin. Using Cox proportional hazards models, we assessed the association of the teeth group (Teethgrp) - consisting of 10 teeth - with cardiovascular and all-cause mortality after 15.8 years of median follow-up.

RESULTS

In multivariate models, with the edentulous state as reference, one level increase in Teethgrp was associated with significantly increased survival from cardiovascular disease (CVD) mortality with a Hazard Ratio (HR) 0.73, p-value = 0.02 but not with all-cause mortality (HR = 0.87, p = 0.13). The findings were not mediated by C-reactive protein (CRP) levels ≥3 mg/L or by median fibrinogen levels, but were mediated by CRP levels >5 mg/L.

CONCLUSION

Each increment of 10 teeth from the edentulous state was associated with a 27% improved CVD survival, independent of low-grade systemic inflammation.

Statistical methods in the Global Enteric Multicenter Study (GEMS)

The Global Enteric Multicenter Study (GEMS) is an investigation of the burden (number of cases and incidence) of moderate-to-severe diarrhea (MSD) in children <60 months of age at 7 sites in sub-Saharan Africa and South Asia. The population attributable fraction for a putative pathogen, either unadjusted or adjusted for other pathogens, is estimated using the proportion of MSD cases from whom the pathogen was isolated and the odds ratio for MSD and the pathogen from conditional logistic regression modeling. The adjusted attributable fraction, proportion of MSD cases taken to a sentinel health center (SHC), number of cases presenting to an SHC, and the site's population are used to estimate the annual number of MSD cases and MSD incidence rate attributable to a pathogen or group of pathogens. Associations with death and nutritional outcomes, ascertained at follow-up visits to case and control households, are evaluated both in MSD cases and in the population.