Using natural experiments to improve public health evidence: a review of context and utility for obesity prevention.
ABSTRACT: BACKGROUND:Natural experiments are increasingly valued as a way to assess the health impact of health and non-health interventions when planned controlled experimental research designs may be infeasible or inappropriate to implement. This study sought to investigate the value of natural experiments by exploring how they have been used in practice. The study focused on obesity prevention research as one complex programme area for applying natural experiment studies. METHODS:A literature search sought obesity prevention research from January 1997 to December 2017 and identified 46 population health studies that self-described as a natural experiment. RESULTS:The majority of studies identified were published in the last 5?years, illustrating a more recent adoption of such opportunities. The majority of studies were evaluations of the impact of policies (n?=?19), such as assessing changes to food labelling, food advertising or taxation on diet and obesity outcomes, or were built environment interventions (n?=?17), such as the impact of built infrastructure on physical activity or access to healthy food. Research designs included quasi-experimental, pre-experimental and non-experimental methods. Few studies applied rigorous research designs to establish stronger causal inference, such as multiple pre/post measures, time series designs or comparison of change against an unexposed group. In general, researchers employed techniques to enhance the study utility but often were limited in the use of more rigorous study designs by ethical considerations and/or the particular context of the intervention. CONCLUSION:Greater recognition of the utility and versatility of natural experiments in generating evidence for complex health issues like obesity prevention is needed. This review suggests that natural experiments may be underutilised as an approach for providing evidence of the effects of interventions, particularly for evaluating health outcomes of interventions when unexpected opportunities to gather evidence arise.
Project description:CONTEXT:The National Academy of Medicine recommends childhood obesity prevention efforts making healthier options the passive choice. This review evaluated the effectiveness of population-level policies and programs from natural experiments for childhood obesity prevention. EVIDENCE ACQUISTION:The search included PubMed, CINAHL, PsycINFO, and EconLit from 2000 to 2017 for policies evaluated by natural experiments reporting childhood BMI outcomes. The studies were analyzed in 2017-2018. Interventions were classified by environmental focus (food/beverage, physical activity, or both) and stratified by setting (school, community, both). Risk of bias was evaluated for each study. EVIDENCE SYNTHESIS:Of 33 natural experiments, most (73%) took place in the school setting only. The most common environmental focus in any setting was food/beverage (48%). All four studies that focused on both food/beverage and physical activity in schools demonstrated decreased prevalence of overweight/obesity or BMI z-score by 0.04-0.17. BMI decreased in all four studies in both school and community settings. The largest effect size was a decrease in BMI z-score of 0.5, but most were <0.25. The risk of bias was high for most (76%) studies. Most (63%) of the eight studies with low/medium risk of bias took place in the school setting focused on the food/beverage environment; effects on BMI were mixed. CONCLUSIONS:Natural experiments evaluating school-based policies focusing on both the food/beverage and physical activity environments (versus targeting only one) consistently showed improvement in BMI. However, most studies had high risk of bias, highlighting the need for improved methods for evaluation of natural experiments for childhood obesity prevention.
Project description:This systematic review collates, and presents as a narrative synthesis, evidence from interventions which included changes to the urban environment and reported at least one health behaviour or outcome for children and young people. Following a comprehensive search of six databases, 33 primary studies relating to 27 urban environment interventions were included. The majority of interventions related to active travel. Others included park and playground renovations, road traffic safety, and multi-component community-based initiatives. Public health evidence for effectiveness of such interventions is often weak because study designs tend to be opportunistic, non-randomised, use subjective outcome measures, and do not incorporate follow-up of study participants. However, there is some evidence of potential health benefits to children and young people from urban environment interventions relating to road safety and active travel, with evidence of promise for a multi-component obesity prevention initiative. Future research requires more robust study designs incorporating objective outcome measures.
Project description:The increasing prevalence of childhood obesity has led to interest in its prevention, particularly through school-based and family-based interventions in the early years. Most evidence reviews, to date, have focused on individual behaviour change rather than the 'obesogenic environment'.This paper reviews the evidence on the influence of the food environment on overweight and obesity in children up to 8 years.Electronic databases (including MEDLINE, EMBASE, Cochrane Controlled Trials Register (CCTR), DARE, CINAHL and Psycho-Info) and reference lists of original studies and reviews were searched for all papers published up to 31 August 2011.Study designs included were either population-based intervention studies or a longitudinal study. Studies were included if the majority of the children studied were under 9 years, if they related to diet and if they focused on prevention rather than treatment in clinical settings.Data included in the tables were characteristics of participants, aim, and key outcome results. Quality assessment of the selected studies was carried out to identify potential bias and an evidence ranking exercise carried out to prioritise areas for future public health interventions.Thirty-five studies (twenty-five intervention studies and ten longitudinal studies) were selected for the review. There was moderately strong evidence to support interventions on food promotion, large portion sizes and sugar-sweetened soft drinks.Reducing food promotion to young children, increasing the availability of smaller portions and providing alternatives to sugar-sweetened soft drinks should be considered in obesity prevention programmes aimed at younger children. These environment-level interventions would support individual and family-level behaviour change.
Project description:Childhood obesity is of increasing concern in many parts of Africa. We conducted a systematic search and review of published literature on behavioural childhood obesity prevention interventions. A literature search identified peer-reviewed literature from seven databases, and unindexed African journals, including experimental studies targeting children age 2-18 years in African countries, published in any language since 1990. All experimental designs were eligible; outcomes of interest were both behavioural (physical activity, dietary behaviours) and anthropometric (weight, body mass index, body composition). We also searched for process evaluations or other implementation observations. Methodological quality was assessed; evidence was synthesised narratively as a meta-analysis was not possible. Seventeen articles describing 14 interventions in three countries (South Africa, Tunisia and Uganda) were included. Effect scores indicated no overall effect on dietary behaviours, with some beneficial effects on physical activity and anthropometric outcomes. The quality of evidence was predominantly weak. We identified barriers and facilitators to successful interventions, and these were largely resource-related. Our systematic review highlights research gaps in targeting alternative settings to schools, and younger age groups, and a need for more rigorous designs for evaluating effectiveness. We also recommend process evaluations being used more widely.
Project description:OBJECTIVE:Food insecurity affects millions of Americans and is associated with a range of adverse health outcomes. Food insecure individuals often obtain food from food pantries/banks, prompting health researchers to implement disease prevention/management interventions at these sites. This review examined the existing peer-reviewed research on disease prevention/management interventions implemented in food pantries/banks. DESIGN:Scoping review. DATA SOURCES:Databases searched included MEDLINE, Web of Science, CINAHL and Cochrane. Search strategies included Medical Subject Headings and key terms, including food pantry, food bank, food shelf, food aid and related concepts. ELIGIBILITY CRITERIA:Studies were included if they described an intervention involving food pantries/banks where at least one biometric indicator was included as an outcome variable. Articles focused solely on the quality of foods distributed, the diet quality of food pantry/bank clients or government food aid programmes were excluded. DATA EXTRACTION AND SYNTHESIS:Extracted data included publication details, intervention type, study design, participant characteristics, study outcomes, and barriers and facilitators of intervention implementation. RESULTS:A total of 3317 articles were assessed for eligibility. Six studies met the predefined inclusion criteria. The studies employed a range of intervention approaches to manage or prevent a number of chronic diseases, including obesity, type 2 diabetes and HIV. The studies examined a range of biometric outcomes, including body mass index, glycated haemoglobin and blood pressure. Information about the food pantries/banks where the interventions were conducted was lacking. The studies documented multiple barriers and facilitators related to costs, sustainability and organisational capacity. CONCLUSIONS:To our knowledge, this is the first review to examine disease prevention and management interventions conducted in food pantries and food banks. Given the high number of households who obtain food from food pantries/banks and the chronic health conditions associated with food insecurity, this review highlights the need for more high-quality research in this setting.
Project description:Before genetic approaches were applied in experimental studies with human populations, they were used by animal and plant breeders to observe, and experimentally manipulate, the role of genes and environment on specific phenotypic or behavioral outcomes. For obvious ethical reasons, the same level of experimental control is not possible in human populations. Nonetheless, there are natural experimental designs in human populations that can serve as logical extensions of the rigorous quantitative genetic experimental designs used by animal and plant researchers. Applying concepts such as cross-fostering and common garden rearing approaches from the life science discipline, we describe human designs that can serve as naturalistic proxies for the controlled quantitative genetic experiments facilitated in life sciences research. We present the prevention relevance of three such human designs: (1) children adopted at birth by parents to whom they are not genetically related (common garden approach); (2) sibling designs where one sibling is reared from birth with unrelated adoptive parents and the other sibling is reared from birth by the biological mother of the sibling pair (cross-fostering approach); and (3) in vitro fertilization designs, including egg donation, sperm donation, embryo donation, and surrogacy (prenatal cross-fostering approach). Each of these designs allows for differentiation of the effects of the prenatal and/or postnatal rearing environment from effects of genes shared between parent and child in naturalistic ways that can inform prevention efforts. Example findings from each design type are provided and conclusions drawn about the relevance of naturalistic genetic designs to prevention science.
Project description:Optimal nutrition plays a crucial role in pregnancy. Maternal malnutrition is a risk factor for maternal, fetal, and neonatal complications and is more prevalent in low and middle-income countries (LMICs). This review aims to study the effectiveness of antenatal macronutrient nutritional interventions on maternal, neonatal, and child outcomes. We searched the CENTRAL, PubMed, Embase, and other databases for randomized controlled trials and quasi-experimental designs on healthy pregnant women in LMICs. We also searched grey literature and reports from Google Scholar, Web of Science, and websites of different organizations. Title/abstract screening, full-text screening, and data extraction filtered 15 studies for inclusion. Balanced energy protein (BEP) supplementation (n = 8) studies showed a reduced incidence of perinatal mortality, stillbirths, low birth weight (LBW) infants, small for gestational age (SGA) babies and increased birth weight. Food distribution programs (FDPs) (n =5) witnessed reduced rates of SGA, stunting, wasting, and increased birth weight and birth length. Studies on intervention for obesity prevention (n = 2) showed reductions in birth weight. Other findings were statistically insignificant. Subgroup analyses were conducted to study the effectiveness of supplementation between regions, location, the timing of supplementation and nutritional status; however, there were a limited number of studies in each subgroup. Data from our review supports the antenatal supplementation of BEP and FDP for the prevention of adverse maternal, neonatal, and child outcomes that can be utilized for future policymaking. However, more research is required before recommending obesity prevention programs.
Project description:Natural experimental studies are often recommended as a way of understanding the health impact of policies and other large scale interventions. Although they have certain advantages over planned experiments, and may be the only option when it is impossible to manipulate exposure to the intervention, natural experimental studies are more susceptible to bias. This paper introduces new guidance from the Medical Research Council to help researchers and users, funders and publishers of research evidence make the best use of natural experimental approaches to evaluating population health interventions. The guidance emphasises that natural experiments can provide convincing evidence of impact even when effects are small or take time to appear. However, a good understanding is needed of the process determining exposure to the intervention, and careful choice and combination of methods, testing of assumptions and transparent reporting is vital. More could be learnt from natural experiments in future as experience of promising but lesser used methods accumulates.
Project description:Background: Childhood obesity prevention interventions delivered by health professionals during the first 1,000 days show some evidence of effectiveness, particularly in relation to behavioural outcomes. External validity refers to how generalisable interventions are to populations or settings beyond those in the original study. The degree to which external validity elements are reported in such studies is unclear however. This systematic review aimed to determine the extent to which childhood obesity interventions delivered by health professionals during the first 1,000 days report on elements that can be used to inform generalizability across settings and populations. Methods: Eligible studies meeting study inclusion and exclusion criteria were identified through a systematic review of 11 databases and three trial registers. An assessment tool based on the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) framework was used to assess the external validity of included studies. It comprised five dimensions: reach and representativeness of individuals, reach and representativeness of settings, implementation and adaptation, outcomes for decision making maintenance and/or institutionalisation. Two authors independently assessed the external validity of 20% of included studies; discrepancies were resolved, and then one author completed assessments of the remaining studies. Results: In total, 39 trials involving 46 interventions published between 1999 and 2019 were identified. The majority of studies were randomized controlled trials (n=24). Reporting varied within and between dimensions. External validity elements that were poorly described included: representativeness of individuals and settings, treatment receipt, intervention mechanisms and moderators, cost effectiveness, and intervention sustainability and acceptability. Conclusions: Our review suggests that more emphasis is needed on research designs that consider generalisability, and the reporting of external validity elements in early life childhood obesity prevention interventions. Important gaps in external validity reporting were identified that could facilitate decisions around the translation and scale-up of interventions from research to practice. Registration: PROSPERO CRD42016050793 03/11/16.
Project description:Multilevel interventions are those that affect at least two levels of influence-for example, the patient and the health care provider. They can be experimental designs or natural experiments caused by changes in policy, such as the implementation of the Affordable Care Act or local policies. Measuring the effects of multilevel interventions is challenging, because they allow for interaction among levels, and the impact of each intervention must be assessed and translated into practice. We discuss how two projects from the National Institutes of Health's Centers for Population Health and Health Disparities used multilevel interventions to reduce health disparities. The interventions, which focused on the uptake of the human papillomavirus vaccine and community-level dietary change, had mixed results. The design and implementation of multilevel interventions are facilitated by input from the community, and more advanced methods and measures are needed to evaluate the impact of the various levels and components of such interventions.