Findings of this section of the thesis are in accord with Objective 3 in that statistically significant differences were found between those who wore complete dentures and the fully dentate with respect to diet, nutrition and nutritional status in the United States civilian, non institutionalized adult population aged 25 years and older.
After adjusting for the influence of potential confounders the intake of specific vegetable and fibre items, total dietary fibre, and blood analytes of nutrients found in fruits and vegetables were lower amongst those who were denture wearers when compared with the fully dentate. The one exception was that no difference was found in the intake of citrus fruit between the fully dentate and the denture wearers. In addition, the results indicated that denture wearers had higher BMI scores than the fully dentate.
This thesis used four different nutrition epidemiologic methods (1) Food Frequency Questionnaire, (2) quantified 24 hour dietary recall interview, (3) biochemical analytes, and (4) anthropometric measure (BMI). Each method yielded results that demonstrated the negative impact of being a denture wearer. The findings demonstrated clearly that complete denture wearers in the United States reported that they had on average 3 fewer intakes of carrots and 3.5 fewer intakes of tossed salads per
month than did adults who were fully dentate. Likewise with respect to whole grain and whole wheat bread consumption, 9 percent fewer denture wearers in the population reported that they had eaten whole grain or whole wheat breads than did the fully dentate. The results were statistically significantly different even after adjusting for the effects of age, gender, socioeconomic status, race-ethnicity, smoking status, and vitamin and mineral supplementation. With respect to nutrient intake, indicative of the reported differences in fibre rich food consumption (carrots, tossed salads, and whole grain and whole wheat breads), the total dietary fibre intake was on average 2 grams lower amongst denture wearers than the fully dentate in the multivariate analysis. Nutritional status was assessed by both levels of biochemical analytes for important nutrients found in vegetables in fruits and Body Mass Index. Mean levels of serum beta carotene, serum folate, and serum vitamin C were 7 ug/dL, 1.5 ng/dL, and 0.08 mg.dL lower, respectively amongst those who wore complete dentures after adjusting for the effects of potential confounders. In addition, the BMI score amongst complete denture wearers was on average 1 point higher than that of the fully dentate in the multivariate analysis.
When the results for food consumption, nutrient intake, biochemical assays, and anthropometric measurement are looked at as a whole and the results contrasted, a consistent picture emerges from these four different methods. The intakes of specific foods which are rich in dietary fibre and nutrients known to have anticarcinogenic and other positive health effects were lower amongst the complete denture wearers. In addition, the corresponding intake of dietary fibre was lower amongst the complete denture wearers when compared with the fully dentate and mirror the findings for foods rich in fibre. Likewise, the blood analyte values were reflective of this lower intake of nutrient rich
foods by denture wearers. And finally, the Body Mass Index score was higher amongst the complete denture wearers which may be indicative of long term effects of food intake patterns which were compromised by impaired oral health status. The consistency of these findings across the four approaches suggests that they were not likely to be an artifact of any one method used. These findings indicate that when contrasted the results were internally consistent, but were the findings externally consistent with those of other studies?
The findings of this thesis support the premise that self reported eating restrictions appear to manifest themselves as significant differences in the intake of important food items on a population basis. Numerous oral health related quality of life studies have included investigations of the extent to which people find that their dental problems affect their ability to chew, eat specific foods, or limit the ability to eat a full range of desired foods. Despite the use of several different instruments to measure the impact of dental problems on oral health related quality of life the results of these studies have demonstrated that in numerous countries denture wearers /edentulous report abroad spectrum of eating related difficulties. Consistently, findings indicated that, when compared with those who are dentate, denture wearers / edentulous were worse off. Studies have shown that the magnitude of the self reported problems are great. For example. Smith and Sheiham (1980) reported that 30 percent of the free living elderly, most of whom (74%) were edentulous, had eating difficulties. Likewise in a study of older adults in South Australia, 14% of the edentulous reported difficulty chewing food fairly or very often (Slade & Spencer, 1994). Slade and Spencer in collaboration with North American colleagues (Slade et al, 1996) compared the results from their study in South Australia with those of Ontario, Canada and North Carolina and found that the
edentulous in most of the communities surveyed reported significantly more social impacts of dental health which included questions regarding difficulty chewing and avoidance of eating than did the dentate. In addition, in Finland, 41 percent of institutionalized elderly reported that they could not eat a full range of desired foods because of dental problems (Ekelund, 1989) and 30% of denture wearers had trouble with their dentures when eating.
Looking next at cross sectional surveys, several focussed specifically on older adults (1) who wore complete dentures (Demers et al, 1996), or (2) who were edentate (Steele et al, 1998). Others have investigated a broader age range of adults such as those aged 30 and over who were edentate with rehabilitation (Ranta et al, 1988) middle aged edentate women (Hailing et al, 1988), edentulous middle aged persons of both sexes (Johansson et al, 1994), and older men (Wayler et al, 1983; Chauncey et al, 1984; Wayler et al, 1984), and edentulous adults (Burt et al, 1982; Joshipura, Willett & Douglass, 1996). These studies, conducted in numerous countries, found that the edentulous and those who had dentures consumed, in general, fewer fruit, vegetables, or root vegetables than their counterparts with better dentition status. The results of the current study of a representative sample of the adult population of the United States are consistent with the findings of other cross sectional studies and found that, even when dentures were worn, people who had lost all of their teeth reported lower consumption of carrots, tossed salads (that typically contain an assortment of nutrient rich vegetables and fruits including tomatoes) and whole wheat and whole grain breads than those who were fully dentate even after adjusting for socioeconomic and behavioural factors.
Studies which focussed solely on the elderly or which did not adjust for the influence of age may legitimately spawn questions as to whether oral factors other than teeth, such as decreased neuromuscular capacity (Duthie etal, 1983; Knapp, 1989), xerostomia (Locker, 1993; Gilbert, Heft & Duncan, 1993; de Jong etal, 1999), or diminished taste acuity (de Jong et al, 1999), were contributors to differential intake of foods in the seniors. These issues warrant further investigation as most lai;ge scale cross sectional studies, including the present study, have not included measures of these domains. However, in this study the influence of age was adjusted for in the multivariate analyses. The consistency of the findings in studies of the elderly, the middle aged, and in studies that adjusted for age lend credence to the argument that denture wearing itself is a determinant of lower intake of some vegetables, fruits and whole grain and whole wheat breads independent of the other oral conditions. Again, questions regarding the influence of other oral health factors warrant further investigation.
The present study found no differences between denture wearers and the fully dentate in the reported consumption of a specific fruit item; citrus fruit. It might be suggested that no differences were found because citrus fruits are seasonal and thus perhaps the NHANES in
study design did not take seasonal variation into account. However, seasonal variation was considered during the planning of NHANES m (Liu, 1992) and while the literature was equivocal on the subject, it was stated that given the rapid development of technologies, food items were available all year round in the United States.
The reported dietary fibre intake of denture wearers in the United States adult population was on average 2 grams lower than that of the fully dentate in the adult population. Several other studies have, during the
past decade, explored the difference in dietary fibre intake between the edentulous or denture wearers and the dentate. While the methods of assessing dietary fibre intake, dental status, and effects of potential confounders varied greatly from study to study, the results by and lai^ge were of a similar magnitude. Specifically, the difference found in dentate and edentulous men who participated in the MONICA-project (Johansson et al, 1994) was 2 grams, Joshipura, Willett and Douglass (1996) found in the male Health Professionals Follow-Up Study a 1 gram difference, Krall, Hayes and Garcia (1998) reported a 4 gram difference in the study of males in the U.S. Veterans Affairs Dental Longitudinal Study, and Steele et al (1998) in the British National Diet and Nutrition Survey of people 65 years and older reported a 3 gram difference. Papas et al (1998) in a pilot study found those with dentures had about a 1 gram lower intake than the dentate. The only study to report a difference outside this general range was that ofMoynihan et al (1994) that was conducted with 30 complete denture wearers attending a dental hospital who were compared with a social class matched group of university employees who were dentate. The researchers found on average that the denture wearers consumed 34 grams of dietary fibre less than the dentate. One explanation for the greater magnitude of difference is that the denture wearers in the Moynihan et al (1994) study may very well have been attending the dental hospital because of problems with their dentures and thus, not surprisingly would have even greater difficulty eating fibrous foods than the edentulous and denture wearers in other studies that were comprised of non dental patients.
The NHANES 111 is one of two contemporary large scale studies to include measures of nutritional status, as well as, dental status, the other being the British National Diet and Nutrition Study (Steele et al, 1998). Looking at the relationship of dental status and nutritional status it was
found that statistically significant differences existed between denture wearers and the fully dentate for important blood analytes of nutrients found in vegetables and fruits, specifically serum beta carotene, serum folate and serum vitamin C. Steele et al (1998) also reported such differences between the edentulous and the dentate for plasma vitamin C and for plasma retinol. The consistency of the findings between these two studies, despite the fact that the NDNS focussed on seniors, did not differentiate denture wearers from non wearers, and did not adjust for the influence of smoking, lends increased credence to the finding that the edentulous, across the adult life span, are at increased risk to having lower intakes of nutrient rich foods which in turn are manifested in lower levels of nutrients available through the blood. Blood analyte levels for folate were not reported in the NDNS study (Steele et al, 1998). However, thirty years ago Makila (1968;1969) in a study of clinic patients found no differences between the denture wearers and age, gender and social status matched dentate subjects for serum folate or for serum ascorbic acid. Likewise, Bates etal (1971) in a study of 3 mining villages found no statistically significant differences between the edentulous and denture wearers with respect to serum folate levels. Neither of these studies adjusted for the influence of smoking and it is possible that differences have been detected in more recent studies because of the use of improved biochemical assaying techniques. While no other studies looked at serum beta carotene, both the studies of Joshipura, Willett and Douglass (1996) and Krall, Hayes and Garcia (1998) found that the intake of carotene was lower amongst the edentulous than for those who had at least 25 teeth or were fully dentate, respectively. Likewise while few studies have used serum folate levels as outcome measures, several have explored folate intake and found that denture wearers consumption of the nutrient was less than that of the
fully dentate (Krall, Hayes & Garcia, 1998) or dentate (McGandy et al, 1986; Papas et al, 1989; 1998).
The finding that there was no difference in the intake in citrus fruit between denture wearers and the fully dentate agrees with those of Steele et al (1998) and Sheiham et al (1999) who reported that no differences were found in intake of oranges between the dentate and edentate in the National Diet and Nutrition Study.
The Body Mass Index amongst denture wearers was higher than that of the fully dentate. The mean BMI of denture wearers in the adjusted model was within the range considered overweight (BMI greater than 24.9) while the fully dentate were within the normal range which is 20- 24.9 (Ulijaszek, 1997). This finding corroborates that of Johansson et al (1994) who, in a study of the middle aged, found that women denture wearers had on average higher BMI scores than the dentate. A plausible explanation of these findings is that denture wearers avoid nutrient dense foods such as fruits, vegetables and whole grains and in their place consume easy to chew foods that are high in non milk extrinsic sugar and fat. Only two other studies assessed this relationship amongst the non institutionalized, Steele et al (1998) and Xie & Ainamo (1999). Both the study of Steele et al (1998) and Xie & Ainamo (1999) focussed on the elderly and found that there were no statistically significant differences between the edentulous and the dentate. These differences in findings between studies that focussed exclusively on the elderly and i two that included younger participants are intriguing. Energy intake is known to decline with advancing age and thus it is feasible the BMI decreased amongst the edentulous to the point that they equalled that of the dentate. The diets of the edentate and dentate may be more similar in advancing years because of a limited range of food choices such as Meals
on Wheels, or institutional foods in adult day care centres. Researchers (Kuczmarski et al, 1994; Flegal et al, 1998) in studies of the prevalence of overweight in the United States, concluded that many factors may be associated with overweight and include dietary knowledge, attitudes, practices, physical activity levels, and “perhaps” factors including social, demographic and health behaviour determinants. It appears from the results of this thesis that, despite wearing dentures, those who have lost all their teeth may be at a disadvantage. While only 3% of the variation was explained by all of the factors in the multivariate model, one third of that variation (1%) was attributable to dental status.
As early as the fifth century B.C., Hippocrates alerted health care providers and citizens to the importance of social and behavioural determinants of health including what one eats and drinks (Porter, 1997). The importance of these broader factors as determinants was underscored recently during a conference entitled “Socioeconomic status and health in industrial nations: social, psychological and biological pathways” (Adler et al, 1999). Looking at the mixed effects of the multivariate models for this thesis, it was found that the greatest amount of variation explained by the models was 23% for serum folate level and the next highest was amount was 10% for dietary fibre. The low coefficient of determination values for multivariate models of this study were of similar magnitude to those found in a study by Kerr et al (1982) which included numerous sociodemographic variables in regression equations, as well. The amount of variance that was explained by dental status ranged in models that were statistically significant from 0.01% to 1%. While the amount of variance explained was low, when viewed within the context of the amount of variance that was explained overall by the wide range of socioeconomic and behavioural factors in the multivariate models, the contribution of dental
status was in several cases (tossed salad, dietary fibre, Body Mass Index) non trivial.
Speakers at the conference on socioeconomic status and health in industrial nations encouraged researchers not to simply adjust for socioeconomic status but also to explore in greater detail the influence of these variables (Adler et al, 1999). Thus the multivariate analyses of this thesis were set up to explore the mixed effects, that is, the analyses did not simply adjust for the influence of potential confounders but rather explored the adjusted effects of each of the covariates net of each other. The adjusted effects of dental status on the multivariate models were consistently highly statistically significant (p <0.0001) whereas the adjusted effects of such variables as socioeconomic status, gender and race/ ethnicity were much less often of significance in the models. For example looking at gender, the findings within the context of the models of this study, were consistent with those of several other cross sectional surveys which indicated that there were differential intakes of vegetable and fruit items by gender (Ranta et al, 1988; Johansson et al, 1994). In the context of this study men who wore dentures had lower intakes of carrots and tossed salad and correspondingly lower levels of serum beta carotene, serum folate and serum vitamin C than did females denture wearers, but they had a greater intake of total dietary fibre. Overall, the influence of socioeconomic status does not appear to be as strong as might have been anticipated. The importance of including measures of race / ethnicity when analysing United States population data is underscored, as Mexican Americans’ intakes of the food items and total dietary fibre, as well as their biochemistry’s were not different from White non Hispanic Americans with the exception of carrots where their intake is greater. The impact of smoking was very clear, smokers consistently had lower intakes of nutritious food items, total dietary
fibre, and lower levels of blood analytes for nutrients found in fruits and vegetables than did those who did not smoke, within the context of the overall model. The findings illustrate the importance of exploring dental status within the broader context of socioeconomic and behavioural factors as a prelude to the development of health promotion research or health promotion initiatives.
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