Thesis
Associations between longitudinal fluoride intakes from birth to age 23 and multi-detector computed tomography (MDCT) bone densitometry outcomes at age 23
University of Iowa
Master of Science (MS), University of Iowa
Spring 2023
DOI: 10.25820/etd.007145
Abstract
While fluoride is widely used as an anti-cavity agent, there have been conflicting findings on its impact on bone health. Given the widespread use of community water fluoridation in the U.S. and increased access to fluoride from other sources (dietary and non-dietary), there have been concerns about the possible greater accumulation of fluoride in developing skeletons of children, adolescents, and young adults. Therefore, there is a need for studies relating bone outcomes to detailed fluoride exposure assessment among children, adolescents, and young adults.
Most previous studies which assessed the effects of water fluoridation on fracture risk or bone mineral density in adults were based on community level data instead of individual level data. Conflicting results, in terms of the effects of fluoride on bone, were obtained from these studies. In the few longitudinal studies that assessed relationships between fluoride intake and bone development in children, adolescents, or young adults, most had small sample sizes and/or utilized less refined densitometry methods. Hence, there is a need for more individual- level fluoride exposure and longitudinal studies to assess the relationships between fluoride intake and bone development. There are especially important gaps in our understanding about the relationships between fluoride and bone development during the adolescent-adult transition period. Thus, analysis of relationships between fluoride intake from birth to age 23 and bone outcomes at age 23 can help to address these gaps.
The aim of this thesis was to assess the relationships between period-specific and cumulative daily fluoride intakes from birth to age 23 and bone densitometry outcomes of the 23-year-old young adults. This thesis project is a secondary data analysis of the previously-collected and de-identified data from the Iowa Fluoride Study (IFS) and the Iowa Bone Development Study (IBDS).
The IBDS is an offshoot of the IFS, a study that tracked the effects of fluoride exposures (both dietary and non-dietary sources) on dental fluorosis and dental caries over time. The IFS recruited participants between 1992 and 1995 from postpartum wards in eight Iowa hospitals. In 1998, the families that were still a part of the IFS were invited to join the IBDS.
Comprehensive study questionnaires were used to collect information on detailed fluoride intakes from water, beverages other than water, selected foods, dietary fluoride supplements, and fluoride dentifrice, as well as oral hygiene practices (i.e., tooth-brushing/dentifrices, mouth rinses), and professional fluoride applications. These questionnaires were sent when the child was aged 1.5, 3, 6, 9, 12, 16, 20, 24, 28, 32, and 36 months and every 6 months after that. Estimated period-specific (0-8, 8-15, and 15-23 years) and cumulative (birth to 23 years) fluoride intakes from combined sources were determined using the collected data. Additional information on dietary calcium, vitamin D and protein intakes, physical activity, and physical maturity was also obtained through specific questionnaires.
Age 23 multi-detector computed tomography (MDCT) scans of the distal tibia were obtained from 330 participants using a SOMATOM Force Scanner at the University of Iowa Comprehensive Lung Imaging Center. Nine cortical and four trabecular bone microstructural outcomes were computed using previously-validated methods. MDCT results of the trabecular bone (volumetric bone mineral content (vBMC), volumetric bone mineral density (vBMD), transpose bone mineral density (tBMD), plate trabecula bone mineral density (pBMD), trabecular network area density (Tb.NA), plate width (TS- PW), trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), erosion index (EI)) and cortical bone (cortical bone porosity over the ROI of 0-10% peel at 4-6% of tibia length (Cb.Poro10P), cortical bone porosity over the ROI of 0- 15% peel at 4-6% of tibia length (Cb.Poro15P), cortical bone porosity (Cb.Poro), and cortical thickness (Cb.Th)) bone were related to longitudinal fluoride intakes through sex-specific bivariate and multivariable analyses, the latter adjusting for height, weight, years since peak height velocity (PHV), vertical jump, dietary calcium intake, Healthy Eating Index-2010 (HEI- 2010) scores, and Physical Activity Questionnaire (PAQ) scores. Due to the multiple statistical analyses being conducted with the same explanatory fluoride variables, p-values <0.01 were considered statistically significant and those with 0.01<p<0.05 were considered statistically suggestive.
The mean daily fluoride intakes estimated using area-under-the-curve (AUC) from birth to 23 years were 0.73-1.12 mg F for males and 0.67-0.93 mg F for females, and they generally increased with age. For the unadjusted one-variable linear regression in females, Tb.vBMC was the only bone measure that had a statistically significant positive association at p<0.01 with period-specific fluoride intake from 8-15 years. Also, statistically suggestive positive associations at 0.01<p<0.05 were found between cumulative fluoride intake from birth to 23 years and each of Tb.vBMC and Tb.vBMD. There were no statistically significant or suggestive negative associations. However, for males, there were no unadjusted correlations found at p<0.01 or 0.01<p<0.05 between period-specific and cumulative fluoride intake variables and distal tibial trabecular measures. In addition, no associations at p<0.01 or 0.01<p<0.05 were found between any of the fluoride intakes and cortical measures for either males or females. For the multivariable linear regression models fully adjusted for height, weight, time since PHV, vertical jump, dietary calcium intakes, HEI-2010 scores, and PAQ scores, none of the period-specific or cumulative fluoride intakes had statistically significant (p<0.01) or statistically suggestive (0.01<p<0.05) correlations with trabecular or cortical bone measures for either sex. Most of the associations were positive, with a few negative ones and they were generally all weak.
The findings of this thesis show that the longitudinal period-specific and cumulative fluoride intakes from combined sources were associated weakly and mostly positively with MDCT bone measures at age 23 years. Hence, fluoride intakes within the optimal range do not appear to have adverse impacts on bone health in young adults in the Midwest region of the United States. Thus, efforts should be continued to preserve and expand community water fluoridation.
Details
- Title: Subtitle
- Associations between longitudinal fluoride intakes from birth to age 23 and multi-detector computed tomography (MDCT) bone densitometry outcomes at age 23
- Creators
- Gurjot Kaur Bhatia
- Contributors
- Steven M. Levy (Advisor)John J. Warren (Committee Member)Punam K. Saha (Committee Member)Erliang Zeng (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Dental Public Health
- Date degree season
- Spring 2023
- DOI
- 10.25820/etd.007145
- Publisher
- University of Iowa
- Number of pages
- xxi, 382 pages
- Copyright
- Copyright 2023 Gurjot Kaur Bhatia
- Language
- English
- Date submitted
- 04/25/2023
- Date approved
- 06/30/2023
- Description illustrations
- Illustrations, tables, graphs, charts
- Description bibliographic
- Includes bibliographical references (pages 374-382).
- Public Abstract (ETD)
Concerns have been raised about the impact of fluoride intake on developing skeletons of young adults, but important gaps exist in our understanding of this relationship. This thesis is a secondary analysis of the previously-collected and de-identified data from the Iowa Fluoride Study/Iowa Bone Development Study (IFS/IBDS) which assessed the relationships between period-specific and cumulative daily fluoride intakes from birth to age 23 years and bone densitometry outcomes of young adults aged 23 years.
The study participants were recruited from the IFS/IBDS Study cohort, which was followed from birth to age 23. Detailed information about combined fluoride intake from all sources was collected through comprehensive study questionnaires. These were administered when the children were ages 1.5, 3, 6, 9, 12, 16, 20, 24, 28, 32, and 36 months and every 6 months after that. In addition, information about detailed dietary intakes, physical activity and sedentary behaviors and physical growth/maturity were obtained from all the participants. Bone scans using advanced densitometry techniques were obtained at age 23.
Results from the statistical analyses reveal that longitudinal fluoride intakes were not significantly associated with bone densitometry outcomes at the micro-architectural level for young adults aged 23 years. In addition, the results show that fluoride intake does not have adverse impact on skeletal development in young adults. Outcomes from this study provide evidence that fluoride intakes within the optimal range of most individuals living in the U.S. Midwest region are not related to harmful effects on bone health. Hence, efforts should be focused on preserving and expanding community water fluoridation.
- Academic Unit
- Preventive and Community Dentistry
- Record Identifier
- 9984425313402771
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