Nut602 Research Methods in Nutrition and Food Science Intervention Studies PDF

Summary

This document provides an overview of intervention studies in nutrition and food science, including pilot studies, randomized controlled trials, and quasi-experimental studies. It discusses different study designs, data collection methods, and statistical considerations for nutritional interventions. The document also includes considerations for population-based fortification strategies.

Full Transcript

NUT602: Research Methods in Nutrition and Food Science Fall Intervention 2024 Studies Intervention Studies 2 ▪ Experimental studies ▪ Hypothesis driven ▪ Have a strong evidence basis ▪ Short term ➔ immediate effect of i...

NUT602: Research Methods in Nutrition and Food Science Fall Intervention 2024 Studies Intervention Studies 2 ▪ Experimental studies ▪ Hypothesis driven ▪ Have a strong evidence basis ▪ Short term ➔ immediate effect of intervention is measured ▪ Long term ➔ effect of intervention is evaluated over weeks, months, years ▪ Pilot studies ▪ Randomized controlled trials ▪ Quasi-experimental studies ▪ Population-based fortification studies Pilot studies 3 ▪ Feasibility or exploratory study ▪ Implemented on a small scale in order to test whether all the study processes operate as anticipated before undertaking a full-scale trial ▪ Provide data on the distribution/variability and timescale of outcome responses ➔ power calculations ▪ May test all, or only some, aspects of a full-scale study ▪ May be single-arm (before and after) studies with no control group ▪ Cost and time-effective to assess potential effects ▪ Data reported in descriptive terms & caution should be exercised when interpreting any statistical tests of significance ▪ Cannot determine the effect of intervention Pilot studies 4 ▪ Inform studies with greater rigor ▪ Randomizing participants to study groups ▪ Increasing the range of populations studied ▪ Using new and/or longer-term outcome measures ▪ Assessing the minimum effective amount (or ‘dose’) to be consumed ▪ Evaluating different forms of presentation or delivery of the nutrient or food… Controlled Studies 5 ▪ Measuring outcomes in participants receiving the active intervention ▪ Measuring outcome in a control group (placebo or no intervention) ▪ Increased confidence that changes observed are directly attributable to the intervention → cause-and-effect statements ▪ Allows seasonal variations to be taken into account ▪ Allows to assess the ‘placebo effect’ can be assessed RCTs: Parallel Design 6 ▪ Each participant receives one intervention ▪ Comparisons between groups made on a between-participant basis RCTs: Cross-over design 7 ▪ Participants receive all interventions under comparison & the design specifies the order of interventions: participants act as their own controls ▪ Comparisons between interventions made on a within-participant basis ▪ Improvement in the precision of comparisons (power of the study) ▪ Reduction in required sample size ▪ A washout period may be required between intervention periods ▪ Avoid contamination or carry-over ▪ A run-in period may be desirable to minimize order effects Parallel or Cross-over design? 8 ▪ Parallel studies ▪ Longer-term interventions ▪ Where a washout period may be ineffective at returning outcome measures to baseline ▪ Where intentionally returning to baseline may be unethical ▪ Cross-over studies ▪ Where participant availability may be restricted and in very short-term studies ▪ Choice of study design depends also on: ▪ Time frame, availability of other resources, and potential roles of confounding factors, such as seasonal variations Quasi-experimental studies 9 ▪ Similar to RCTs but they lack key features of a true experiment ▪ Random assignment to the intervention or control group is absent ▪ Control group is lacking altogether ▪ Often used in public health (community food-based interventions) ▪ Provide valuable information about potential usefulness of an intervention, but their internal validity will be compromised Quasi-experimental studies 10 ▪ Before-and-after study without a control group ▪ Data are collected before and after an intervention takes place ▪ No control group for comparison ▪ Impossible to be certain that any differences that have occurred between the start and end of the study are directly attributable to the intervention ▪ Before-and-after study with a non-equivalent groups ▪ One group is assigned to the intervention and another group acts as control group ▪ Groups are not created through random assignment → they may not be similar in all key aspects at the start of the study ▪ May affect the outcome of the study and its internal validity (impossible to conclude that the intervention was causally related to the study outcome) Population-based fortification studies 11 ▪ Implemented as part of public health policy to correct dietary deficiencies ▪ Require careful planning and consideration of a wide range of background scientific data ▪ Examination of high-quality data on the dietary intake (usual food intake and dietary patterns) and nutritional status of the population ▪ Calculation of the dose and most appropriate form of micronutrient to add Methodological Considerations 12 Ethical approval & study Hypothesis Duration registration Intervention Amount nutrient, food, Control consumed diet Recruitment & Outcome Eligibility participant flow measure Data Collection 13 Background Background diet & health, lifestyle change in diet status & change Adverse events Compliance 14 Documenting participant flow Unique study number for each participant Statistical Considerations 15 Randomization Concealment Blinding Analysis Size Per protocol Intention-to-treat Planning a dietary 16 intervention 17 Take-home message 18 Randomized Clinical Trials of Nutritional Interventions – YouTube Recap 19 Aschengrau, A., Seage, G. R. (2020). Essentials of Epidemiology in Public Health. United States: Jones & Bartlett Learning.

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