Completion Rates of Food Frequency Questionnaires and Food Records in People with Chronic Conditions: Systematic...

Background/Objectives: Dietary assessment tools are essential for quantifying food and nutrient intake, characterising dietary patterns, and informing nutrition research. Food Frequency Questionnaires (FFQs) and Food Records (FRs) are widely implemented in observational studies, but completion rates vary, which may compromise data quality, introduce bias, and limit the interpretation of findings. This review is intended to synthesise evidence from observational studies on completion rates of these tools in populations with chronic conditions. Methods: A systematic search of Medline, PubMed, Scopus, and Google Scholar was completed. Eligible studies were observational studies using an FFQ or FR published from January 2015 to May 2025 in people with a chronic condition. Methodological quality was evaluated using the Hoy Risk of Bias tool for observational studies of prevalence. Subgroup meta-analyses estimated pooled mean completion proportions with 95% confidence intervals, and heterogeneity was assessed using the I² statistic. This study was registered with the International Prospective Register of Systematic Reviews and reported according to PRISMA guidelines. Results: Of the 8921 records screened, 88 studies (n = 84,579 participants) met inclusion criteria. The combined FFQ and food record mean pooled completion rate was 79.1% (95% Confidence Interval (CI): 74.37-83.43%). However, substantial heterogeneity was observed, indicating considerable variability across studies. Subgroup analyses highlighted important differences by tool type, format, age group, and disease category. FFQs demonstrated higher completion rates (80.6%) than FRs (74.3%). Electronic formats had higher completion rates than paper formats. Completion rates were higher in adults than in pediatric cohorts, and varied by chronic condition type, with kidney disease associated with the highest completion rates. Conclusions: These findings highlight the importance of considering tailored dietary data collection strategies, particularly for paediatric and medically complex populations, and provide direction for enhancing the feasibility of dietary assessment collection in future research.