Timing of First Sugar Exposure and Dental Caries Experience at 48 Months of Age: A Longitudinal Analysis Nested Within a Birth Cohort

Technical Summary: Timing of First Sugar Exposure and Dental Caries Experience at 48 Months of Age

Problem Statement
Early Childhood Caries (ECC) is a prevalent non-communicable disease resulting from a complex interaction between oral biofilm bacteria and fermentable carbohydrates. While the World Health Organization (WHO) advises against introducing foods or drinks containing added sugars to children under two years of age, the specific impact of the timing of first sugar exposure and the frequency of consumption during the first year of life on ECC development remains a subject of investigation. Existing literature suggests that early sugar exposure may double the likelihood of ECC, yet findings regarding the specific trajectories of sugary food intake and their association with caries outcomes have been mixed. This study addresses the gap in understanding whether the age of sugar introduction and the frequency of added sugar consumption in the first year of life are statistically associated with ECC prevalence and severity at 48 months of age.

Methodology
The study employed a longitudinal design nested within a birth cohort, following the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. The target population consisted of infants born between August 2017 and July 2018 at the University Hospital of Brasília (HUB), excluding those admitted to the Intensive Care Unit.

• Sample: From an initial cohort of 969 invited mothers, 183 children with complete data at both 12-month and 48-month follow-ups were included in the final analysis.
• Data Collection:
  • Dietary Variables: At 12 months, parents reported the age of first sugar exposure, frequency of added sugar use (categorized as none, once daily, or ≥2 times daily), and consumption of specific sugary products (processed foods, sweetened yoghurt, Maizena® biscuits, filled biscuits, boxed juice).
  • Oral Hygiene: Parents reported oral hygiene practices and the use of fluoridated toothpaste.
  • Socioeconomic Factors: Maternal age at childbirth and household head education (dichotomized as <11 years or ≥11 years) were recorded.
  • Clinical Assessment: At 48 months, dental examinations were conducted using the Caries Assessment Spectrum and Treatment (CAST) instrument to determine caries presence, severity (pre-morbidity, morbidity, severe morbidity, mortality), and the number of carious teeth.
• Statistical Analysis: Four regression models were defined a priori using a hierarchical conceptual framework. Poisson regression with a log link was used for binary outcomes (caries presence), and negative binomial regression was used for count outcomes (number of carious teeth) due to data overdispersion. Models adjusted for distal socioeconomic factors, child characteristics, dietary exposure, and oral hygiene behaviors.

Key Results

• Sugar Exposure: All 183 children were exposed to free sugars within the first year of life, with the majority (69.6%) introduced between 8 and 12 months of age. Notably, while 54.1% of parents reported not adding sugar during food preparation, 67.8% of children consumed processed foods, and 78.7% consumed Maizena® biscuits, indicating high exposure to hidden sugars.
• Caries Prevalence: At 48 months, 48.1% of the children exhibited caries experience (including non-cavitated and cavitated lesions). Among affected children, 31.1% had reached the morbidity stage or higher. The mean number of carious teeth was 2.9 (SD = 4.0).
• Associations: No statistically significant associations were identified between early sugar exposure variables and dental caries outcomes at 48 months.
  • Sugar Introduction Age: Prevalence Ratios (PR) were 1.01 (95% CI: 0.95–1.08) for caries presence and 1.00 (95% CI: 0.92–1.08) for caries count.
  • Frequency of Added Sugar: Comparing "no added sugar" vs. "≥2 times/day" yielded a PR of 0.89 (95% CI: 0.57–1.38) for caries presence and 0.64 (95% CI: 0.37–1.12) for caries count. Similar non-significant results were found for the "once/day" vs. "≥2 times/day" comparison.
• Oral Hygiene: 95.1% of children received oral hygiene at 12 months, though only 47.5% used a toothbrush with fluoridated toothpaste.

Key Contributions
The study contributes to the field by providing longitudinal data on the specific timing and frequency of sugar exposure in a Brazilian birth cohort and its relationship to ECC at 48 months. It highlights a discrepancy between parental reporting of "no added sugar" and the actual high consumption of processed sugary foods, suggesting a gap in parental knowledge regarding hidden sugars. Furthermore, the study documents a high prevalence of ECC (48.1%) despite high rates of oral hygiene initiation, underscoring the multifactorial nature of the disease.

Significance and Claims
The authors conclude that, within this specific cohort, neither the age of first sugar introduction nor the reported frequency of added sugar consumption up to 12 months was associated with caries experience or severity at 48 months. The paper posits that these null findings may be attributed to:

1. Lack of Variability: The high prevalence of sugar consumption across the entire sample (all children were exposed) and the homogeneous distribution of oral hygiene practices reduced the contrast between exposure groups, limiting the ability to detect statistical associations.
2. Multifactorial Etiology: The results reinforce that ECC is influenced by a complex interplay of behavioral, socioeconomic, and dietary factors beyond the simple timing of sugar introduction.
3. Public Health Implication: The findings suggest that preventive strategies should extend beyond isolated recommendations on sugar timing. Instead, they should address broader dietary patterns, nutritional literacy regarding processed foods, and the food environment. The authors note that while reducing sugar intake and promoting fluoridated toothpaste are standard recommendations, they may be insufficient on their own to prevent new lesions without addressing contextual determinants.

The study acknowledges limitations, including the single time-point assessment of diet at 12 months, potential recall bias in parental reporting, and a sample size that may have been insufficient to detect modest effects (increasing Type II error risk). Consequently, the authors advocate for future longitudinal studies with larger samples to better capture the cumulative impact of sugar consumption.