Abstract
Objectives. We assessed the impact of health literacy and acculturation on oral health status of Somali refugees in Massachusetts.
Methods. Between December 2009 and June 2011, we surveyed 439 adult Somalis who had lived in the United States 10 years or less. Assessments included oral examinations with decayed, missing, and filled teeth (DMFT) counts and measurement of spoken English and health literacy. We tested associations with generalized linear regression models.
Results. Participants had means of 1.4 decayed, 2.8 missing, and 1.3 filled teeth. Among participants who had been in the United States 0 to 4 years, lower health literacy scores correlated with lower DMFT (rate ratio [RR] = 0.78; P = .016). Among participants who had been in the country 5 to 10 years, lower literacy scores correlated with higher DMFT (RR = 1.37; P = .012). Literacy was not significantly associated with decayed teeth. Lower literacy scores correlated marginally with lower risk of periodontal disease (odds ratio = 0.22; P = .047).
Conclusions. Worsening oral health of Somali refugees over time may be linked to less access to preventive care and less utilization of beneficial oral hygiene practices.
Among refugees newly arrived in Massachusetts, oral abnormalities are the most common health problem in children1 and the second most common problem in adults. One major determinant of oral health disparities is access to preventive and restorative dental care.2 Other determinants include oral hygiene practices and diet.2 Linguistic and cultural factors may play important roles in determining access to oral health services as well as personal oral hygiene practices, and limited literacy skills have been hypothesized as a likely barrier to better oral health outcomes.3
Health literacy, reflecting an individual’s capacity to obtain, process, and understand basic health information and services, affects a variety of determinants of oral health and is thought to play a pervasive role in all aspects of health care and oral health status.3,4 Inadequate health literacy has been associated with a long and growing list of adverse health outcomes.5 Inadequate literacy has been associated with limited access and utilization of care,6,7 poor clinical outcomes,8 hospitalization,9 and mortality.10 However, the relationship between health literacy and oral health has never been studied in a refugee population.
Somalis compose one of the largest refugee populations to have entered the United States in recent years. As a result of civil war over the past 20 years, many Somalis have lived in refugee camps for long periods. More recently arrived Somalis have very low English literacy.11 Somalis are almost all practicing Muslims and have relative homogeneity of language, culture, and religion.12,13 In the United States, Somali refugees have also tended to cluster geographically through a process known as secondary migration to create cohesive communities. Past research indicated a strong role for such social structures as moderators of health literacy and its impact on health status.14 A refugee with low literacy may be able to effectively access care with the help of the community network. Thus, health literacy may function differently in the context of the Somali community, with its strong social support network. The degree to which an individual identifies with the traditional community and social structure or that of the dominant, host community varies and may affect how an individual negotiates competing priorities related to personal oral hygiene, diet, and access to dental care.
Behavioral acculturation is a measure of such factors as with whom people spend time, the types of media they are exposed to, the language in which they feel most comfortable conversing and reading, and with whom they identify. The effects of acculturation on oral health have been studied in Haitian immigrants in the United States who had a low baseline rate of caries. Acculturation was found to be associated with lower rates of development of caries.15 In Australia, a study of Vietnamese refugees revealed associations between acculturation and dental health status.16 The Vietnamese also had very good oral health status, and those with extensive acculturation had even better oral health status. This finding suggested that more acculturation led to protective practices and care that added to those of the refugees’ traditional culture.
However, the findings documented a nonlinear relationship in which refugees with moderate levels of acculturation had worse oral health status. The researchers hypothesized that the cultural marginality model, previously applied to oral health research,17,18 offered an explanation: refugees with moderate levels of acculturation were alienated from their traditional culture without adequate integration into the dominant culture. Thus, moderately acculturated refugees might adopt behaviors deleterious to oral health, such as Western dietary habits, without adopting preventive aspects of Western oral hygiene and related behaviors.16 By contrast, individuals with a low level of acculturation may have continued beneficial traditional practices and not adopted a cariogenic Western diet. In the Somali community, one such practice might be use of a stick brush (miswak or aday). Studies have found stick brushes to be effective in removing plaque.11,19 These brushes also have an inhibitory effect on oral cariogenic streptococci20,21 and periodontal pathogens.21
In light of the importance of health literacy to health in the general population, we sought to determine the relationship of health literacy (assessed in English) with oral health clinical outcomes of Somali refugees in Massachusetts. We hypothesized that after control for acculturation, participants with high health literacy would be more likely than others to have (1) less lifetime history of decay, untreated dental decay, and periodontal disease; (2) a higher rate of traditional or Western personal hygiene practices and behaviors known to be associated with better oral health outcomes; and (3) more utilization of professional dental care for preventive services. We also assessed functional and mental health outcomes and a variety of social and cultural factors relevant to the effects of literacy, acculturation, oral health care, and personal hygiene practices on oral health status in the Somali community.
METHODS
Our cross-sectional survey entailed structured interviews of a convenience sample of Somali adults living in Massachusetts. All contacts with participants, informed consent, interviews, and examinations were conducted in Somali by a Somali research assistant and dental examiner. With the exception of the literacy measure, all written materials were translated into Somali to enhance standardization of the interviews. The translation process followed standard procedures for group, consensus translation.22
Data Collection
Individual refugees were eligible for the study if they were aged 18 years or older, had arrived from overseas no more than 10 years prior to enrollment, and were of Somali nationality. Exclusion criteria were functional visual impairment sufficient to prevent reading of test materials; medical diagnoses known to interfere with speech articulation; known cognitive impairment, learning disabilities, or traumatic brain injury; and medical diagnoses requiring antibiotic prophylaxis for oral examination. We recruited by word of mouth and then by snowball technique.
We used purposive sampling to ensure that the sample was representative of the general population of Somali refugees in Massachusetts with respect to age and gender. Specifically, we targeted age and gender groups for enrollment to match the distribution that would be expected in 2009 in the cohort of Somali refugees for whom the Refugee and Immigrant Health Program of the Massachusetts Department of Public Health received formal notification of arrival in Massachusetts since 1999. Women in this population had the following age distribution: 25% were expected to be aged 18 to 24 years in 2009, 51% to be aged 25 to 44 years, 16% to be aged 45 to 64 years, and 8% to be aged 65 years or older. Among the male Somali population, 27% were expected to be aged 18 to 24 years, 51% to be aged 25 to 44 years, 15% to be aged 45 to 64 years, and 6% to be aged 65 years or older.
We conducted most interviews during the typical workweek, but we also interviewed individuals outside of routine daytime business hours to facilitate enrollment of working participants. Participants received a $50 gift card on completion of the interview. Twenty percent (n = 84) of participants also participated in an extended qualitative interview, conducted by 2 medical anthropologists. These detailed, semistructured interviews explored domains of the Eraker theoretical model of health decision-making.23 Four members of the study team thematically coded transcripts of the interviews and then analyzed them with HyperRESEARCH version 2.8.3 (ResearchWare Inc, Randolph, MA). We used the qualitative findings, which will be reported in detail elsewhere, to guide analysis and interpretation of the quantitative data.
The research interview comprised questions on demographics, cultural practices, educational experiences, oral health practices, and experience with dental care services. In addition, it assessed dental and oral health care experiences through the Access to Care Questionnaire of the Basic Screening Survey.24 Questions on access to medical care came from the National Health Interview Survey25; these were supplemented with questions regarding personal care and lifestyle practices relevant to oral health.
We assessed functional health literacy with the Short Test of Functional Health Literacy in Adults (STOFHLA),26 a 36-item test of reading comprehension that uses a set of sentences from medical scenarios with key words missing. Participants select words to complete the sentences from a list provided. The test has high internal consistency and correlates well with other health literacy tests. We dichotomized scoring of the STOFHLA as low (0–22 = inadequate) and higher (23–36 = marginal or adequate).
We assessed functional health with the Medical Outcomes Study Short-Form 12-item survey,27 oral health quality of life with the Oral Health Quality of Life Instrument,28 and acculturation with a revised Haitian Acculturation Scale.15 Because of concern about the impact of mental illness on functional and oral health status, we assessed mental health with the Posttraumatic Stress Disorder Checklist–Civilian Version29 and the Patient Health Questionnaire for depression.30,31 For the depression questionnaire, we first screened participants with the 2-item version and followed up with the remaining 7 items if a participant gave a positive response to the first 2 items.32
A trained and calibrated examiner conducted an oral examination of each participant with a portable light source, dental mirror, explorer, and periodontal probe. For the caries assessment, each tooth present in the mouth was classified as sound, decayed, missing, or filled, according to Modified Basic Screening Survey criteria.24 We presumed that filled teeth had had decay and designated these as DFT (decayed and filled teeth). We classified decayed but unfilled teeth as DT. Periodontal assessment followed World Health Organization criteria, with the Community Periodontal Index of Treatment Needs probe.18 The examiner probed all teeth in each sextant and classified each tooth: no need for care (0), bleeding gingiva on probing (1), presence of calculus and other plaque-retentive factors (2), 4- or 5-millimeter periodontal pockets (3), or pockets 6 millimeters or more deep (4). The score for the tooth in each sextant with the worst condition (highest score) was recorded as the overall score for each sextant. We then classified overall dental condition into 4 levels to reflect the amount of treatment needed and the urgency of need.
Analyses
Analyses focused on 3 main oral health outcome measures derived from oral examinations: (1) the mean number of decayed, missing, and filled teeth (DMFT; representing the lifetime history of decay); (2) the ratio of the number of decayed teeth to the total number of decayed and filled teeth, DT/(DT + DFT), representing the proportion of untreated carious teeth; and (3) the Community Periodontal Index of Treatment Needs score. For analysis, we dichotomized the DT/(DT + DFT) ratio and the index score. Participants with a ratio greater than 0.5 were considered to have high unaddressed decay, and those with an index score of 3 or 4 in any sextant were considered to have periodontal disease.
We also examined several secondary measures—DT, DFT, and missing teeth. For analyses, we selected several main domains of predictor variables that we considered to be likely to affect oral health status: acculturation, sociodemographic factors, oral health practices, and general mental and physical health scores. We categorized acculturation scores from the revised Haitian Acculturation Scale into low, medium, and high according to their distribution.15 Sociodemographic factors were gender, age, ethnicity, education, years lived in the United States, and income. Oral health practices were type of dental insurance, preventive care within the past year, restorative care within the past year, regular tooth brushing, and use of the stick brush.
Initial analyses were bivariate comparisons of health literacy with the dental health outcome measures. Multivariate analyses then included the literacy measure, selected confounders, and an interaction term between the risk variable (literacy) and years lived in United States. We added the interaction term after preliminary analyses determined that the relationship between oral health status and literacy was affected by time lived in the United States. To build more parsimonious models, we used the backward elimination procedure, with a 0.2 α level for variables to stay in the model.
Because of the distribution of the data and low numbers in some categories, we used zero-inflated Poisson models (SAS Proc GENMOD; SAS Institute Inc, Cary, NC) for DMFT, DT, DFT, and missing teeth. Further analyses used logistic regressions (SAS Proc GENMOD) for high unaddressed decay and presence of periodontal disease. We performed all statistical analyses with SAS version 9.2.
RESULTS
A total of 439 refugees aged 18 years and older participated; 58.1% were women. The sample population roughly approximated the expected distribution of age and gender in the larger Somali community of Massachusetts. Among women, older adults were somewhat overrepresented (age 45–64 years, 22% vs 16% in the Somali community), and younger adults were somewhat underrepresented (25–44 years, 47% vs 51%). Among men, young adults were overrepresented (18–24 years, 39% vs 27%), and the next-youngest age group was underrepresented (25–44 years, 36% vs 51%). These patterns reflect the greater difficulty in enrolling employed, younger adults. By ethnicity, 87% of study participants were ethnic Somalis, and 13% were Somali Bantu. All had arrived in the United States within the past 10 years. Only 2% arrived directly from Somalia; others arrived from Kenya (78%), Ethiopia (9%), and 15 other countries. Most participants reported low or very low income, and 75% had less than a high school education.
Oral Health and Literacy
At some point during their time in the United States, 63% of participants had seen a dentist, and 53.6% had done so in the past year. Nearly all participants (98%) reported brushing their teeth at least daily, and use of dental floss was reported by 40%. Use of the traditional stick brush was reported by 43%. In bivariate analyses of descriptive demographic variables, we found several significant differences between STOFHLA literacy levels. Participants with lower STOFHLA literacy were more likely than those with higher STOFHLA scores to be less acculturated, female, older, Bantu, lacking any formal education, and insured by Medicaid; they were less likely to report brushing their teeth more than once daily (all, P < .05; Table 1). In addition, those with lower literacy were more likely to use a traditional stick brush.
TABLE 1—
Demographic and Health Literacy Characteristics of a Somali Refugee Sample in Massachusetts: December 2009–June 2011
| Characteristic | Total (n = 439) | STOFHLA Score 0–22 (n = 326) | STOFHLA Score 23–36 (n = 113) | P |
| Acculturation level, no. (%) | ||||
| 1 (less acculturated) | 148 (33.7) | 148 (45.4) | 0 (0.0) | <.001 |
| 1–2 | 147 (33.5) | 130 (39.9) | 17 (15) | |
| > 2 | 144 (32.8) | 48 (14.7) | 96 (85) | |
| Gender, no. (%) | ||||
| Male | 184 (41.9) | 118 (36.2) | 66 (58.4) | <.001 |
| Female | 255 (58.1) | 208 (63.8) | 47 (41.6) | |
| Age, y, no. (%) | ||||
| 18–24 | 140 (31.9) | 77 (23.6) | 63 (55.8) | <.001 |
| 25–44 | 186 (42.4) | 145 (44.5) | 41 (36.3) | |
| ≥ 45 | 113 (25.7) | 104 (31.9) | 9 (8) | |
| Ethnicity, no. (%) | ||||
| Somali | 382 (87) | 271 (83.1) | 111 (98.2) | <.001 |
| Bantu | 57 (13) | 55 (16.9) | 2 (1.8) | |
| Education, no. (%) | ||||
| None | 163 (37.1) | 155 (47.5) | 8 (7.1) | <.001 |
| < high school | 168 (38.3) | 128 (39.3) | 40 (35.4) | |
| ≥ high school | 108 (24.6) | 43 (13.2) | 65 (57.5) | |
| Income/mo, $, no. (%) | ||||
| < 1000 | 284 (72.1) | 221 (74.2) | 63 (65.6) | .117 |
| ≥1000 | 110 (27.9) | 77 (25.8) | 33 (34.4) | |
| Years in United States, no. (%) | ||||
| 0–4 | 262 (59.7) | 198 (60.7) | 64 (56.6) | .504 |
| 5–10 | 177 (40.3) | 128 (39.3) | 49 (43.4) | |
| Dental insurance, no. (%) | ||||
| Medicaid/government/HMO | 353 (82.9) | 276 (87.3) | 77 (70) | <.001 |
| Private | 30 (7) | 9 (2.8) | 21 (19.1) | |
| None | 43 (10.1) | 31 (9.8) | 12 (10.9) | |
| Brush teeth ≥2 times/d, no. (%) | ||||
| Yes | 327 (74.5) | 229 (70.2) | 98 (86.7) | <.001 |
| No | 112 (25.5) | 97 (29.8) | 15 (13.3) | |
| PCS | ||||
| Mean (SD) | 52.056 (6.712) | 51.377 (7.105) | 54.075 (4.873) | <.001 |
| Median (range) | 55.09 (18.95–64.7) | 53.47 (18.95–64.7) | 55.09 (29.04–63.38) | |
| MCS | ||||
| Mean (SD) | 60.619 (6.275) | 60.796 (5.979) | 60.094 (7.086) | .324 |
| Median (range) | 62.49 (20.68–75.34) | 62.49 (29.33–75.34) | 62.49 (20.68–65.36) | |
| PCL score | ||||
| Mean (SD) | 20.529 (5.603) | 20.38 (4.794) | 20.955 (7.461) | .350 |
| Median (range) | 18 (17–77) | 18 (17–48) | 18 (17–77) |
Note. HMO = health maintenance organization; MCS = Mental Component Summary Scale of the Medical Outcomes Study Short-Form 12-item survey; PCL = Posttraumatic Stress Disorder Checklist–Civilian Version; PCS = Physical Component Summary Scale of the Medical Outcomes Study Short-Form 12-item survey; STOFHLA = Short Test of Functional Health Literacy in Adults. The sample size was n = 439.
On examination, participants had an average of 1.39 decayed, 2.76 missing, and 1.34 filled teeth. Periodontal disease was noted in 6.5%. The distribution of DMFT and periodontal disease prevalence by demographic variables is presented in Table 2. The prevalence of these varied over time in the United States and with age. In addition, they tended to be more prevalent among participants with no education, Somali ethnicity, and lower income levels. Prevalence was higher among women for DMFT and among men for periodontal disease (Table 2).
TABLE 2—
Decayed, Missing, and Filled Teeth and Prevalence of Periodontal Disease in a Somali Refugee Sample in Massachusetts: December 2009–June 2011
| Characteristic | Decayed Teeth, Mean (Range) | Missing Teeth, Mean (Range) | Filled Teeth, Mean (Range) | Decayed, Missing and Filled Teeth, Mean (Range) | Periodontal Disease, No. (%) |
| Age, y | |||||
| 18–24 | 0.76 (0–12) | 1.56 (0–9) | 1.15 (0–13) | 3.48 (0–17) | 4 (2.9) |
| 25–44 | 1.44 (0–17) | 2.22 (0–12) | 1.37 (0–12) | 5.02 (0–28) | 10 (5.4) |
| ≥ 45 | 2.11 (0–19) | 5.13 (0–32) | 1.54 (0–14) | 8.78 (0–32) | 14 (13.0) |
| Gender | |||||
| Male | 1.02 (0–19) | 2.14 (0–15) | 1.25 (0–13) | 4.41 (0–25) | 15 (8.2) |
| Female | 1.67 (0–17) | 3.21 (0–32) | 1.41 (0–14) | 6.28 (0–32) | 13 (5.2) |
| Education | |||||
| None | 2.33 (0–19) | 3.53 (0–32) | 1.02 (0–11) | 6.89 (0–32) | 17 (10.6) |
| < high school | 0.83 (0–12) | 2.22 (0–15) | 1.56 (0–14) | 4.61 (0–24) | 4 (2.4) |
| ≥ high school | 0.85 (0–14) | 2.44 (0–12) | 1.48 (0–12) | 4.77 (0–25) | 7 (6.5) |
| Years in United States | |||||
| 0–4 | 1.73 (0–19) | 2.47 (0–15) | 1.14 (0–14) | 5.35 (0–24) | 13 (5.0) |
| 5–10 | 0.89 (0–16) | 3.19 (0–32) | 1.64 (0–12) | 5.72 (0–32) | 15 (8.7) |
| Ethnicity | |||||
| Somali | 1.38 (0–19) | 2.88 (0–32) | 1.47 (0–14) | 5.73 (0–32) | 23 (6.1) |
| Bantu | 1.49 (0–9) | 1.96 (0–18) | 0.51 (0–10) | 3.96 (0–25) | 5 (8.9) |
| Income/mo, $ | |||||
| < 1000 | 1.43 (0–19) | 2.74 (0–32) | 1.23 (0–14) | 5.39 (0–32) | 16 (5.7) |
| ≥ 1000 | 1.45 (0–12) | 2.40 (0–15) | 1.38 (0–10) | 5.23 (0–23) | 9 (8.1) |
| Total | 1.39 (0–19) | 2.76 (0–32) | 1.34 (0–14) | 5.5 (0–32) | 28 (6.5) |
Note. The sample size was n = 439.
Of the total sample, 326 (74.3%) had low health literacy. Bivariate analysis showed a trend of higher DMFT count in the low-literacy group. Mean DMFT was 5.8 in the low-STOFHLA group and 4.7 in the high-STOFHLA group (P = .085). In the multivariate analysis, the number of years a participant had lived in the United States at the time of the interview appeared to be an effect modifier, so analyses stratified the relationship between STOFHLA and DMFT by years in the United States (0–4, 5–10 years). In the adjusted analysis, among participants living in the United States for 0 to 4 years, DMFT count (lifetime history of dental decay) was 1.3 times as high among participants with high as those with low STOFHLA scores (for the newer immigrants with low literacy, rate ratio [RR] = 0.78; P = .02). By contrast, among participants living in the United States for 5 to 10 years, those with low STOFHLA scores had 1.4 times the lifetime history of dental decay of those with higher scores (RR = 1.37; P = .01). Those with medium acculturation had 20% less lifetime history of decay than those with high levels of acculturation (P = .02). Somalis had 1.76 times the lifetime history of disease as Bantus (P < .001). Those who did not use the stick brush had 1.20 times the lifetime history of disease of those who did (P = .001; Table 3).
TABLE 3—
Decayed, Missing, and Filled Teeth and Health Literacy Score Stratified by Time in United States Among a Somali Refugee Sample in Massachusetts: December 2009–June 2011
| Characteristic | Adjusted RR (95% CI) |
| STOFHLA score,a low vs high | |
| 0–4 y in United States | 0.78 (0.64, 0.96) |
| 5–10 y in United States | 1.37 (1.07, 1.74) |
| Acculturation | |
| Low vs high | 0.94 (0.76, 1.16) |
| Medium vs high | 0.80 (0.67, 0.95) |
| Women vs men | 1.12 (1.01, 1.25) |
| Age, y | |
| 25–44 vs 18–24 | 1.46 (1.27, 1.69) |
| ≥ 45 vs 18–24 | 2.05 (1.76, 2.39) |
| Somali vs Bantu | 1.76 (1.45, 2.13) |
| Education | |
| None vs ≥ high school | 1.29 (1.10, 1.52) |
| < high school vs ≥ high school | 1.07 (0.93, 1.24) |
| Income/mo: ≥ $1000 vs < $1000 | 1.11 (0.98, 1.25) |
| Dental insurance | |
| Medicaid/government/HMO vs none | 0.81 (0.69, 0.96) |
| Private vs none | 0.80 (0.62, 1.03) |
| Dental exam in past y: yes vs no | 1.23 (1.09, 1.38) |
| Treatment in past y: yes vs no | 1.26 (1.12, 1.42) |
| Brush teeth: no vs yes | 1.109 (0.99, 1.24) |
| Use stick brush: no vs yes | 1.20 (1.09, 1.33) |
| PCL | 1.01 (1.01, 1.02) |
| SF12 | |
| PCS | 0.99 (0.99, 1.00) |
| MCS | 0.99 (0.98, 1.00) |
Note. CI = confidence interval; HMO = health maintenance organization; MCS = Mental Component Summary Scale of the Medical Outcomes Study Short-Form 12-item survey; PCL = Posttraumatic Stress Disorder Checklist–Civilian Version; PCS = Physical Component Summary Scale of the Medical Outcomes Study Short-Form 12-item survey; RR = rate ratio; SF = Medical Outcomes Study Short-Form 12-item survey; STOFHLA = Short Test of Functional Health Literacy in Adults. The sample size was n = 439.
Low = 0–22; high = 23–36.
Oral Health Ratio and Periodontal Disease
In the unadjusted analysis, a high DT/(DT + DFT) ratio was highly associated with low health literacy. The proportion of participants with a high ratio in the low-literacy group was almost twice as high as in the high-literary group (38% vs 19%; P < .001). However, the adjusted model, designed to reflect the relationship between STOFHLA and untreated decay (DT/(DT + DFT)), did not show a statistically significant association between them. Among participants living in the United States for 5 to 10 years, analyses revealed a pattern opposite to the one between STOFHLA and DMFT. Participants with low acculturation had 2.75 times the likelihood of untreated decay as those with high acculturation (P = .01). Participants with medium acculturation did not differ significantly from those with high acculturation (Table 4).
TABLE 4—
Association Between Untreated Decay and Health Literacy Score After Control for Acculturation and Other Factors Among a Somali Refugee Sample in Massachusetts: December 2009–June 2011
| Characteristic | AOR (95% CI) |
| STOFHLA score,a low vs high | |
| 0–4 y in United States | 1.77 (0.73, 4.32) |
| 5–10 y in United States | 0.59 (0.20, 1.76) |
| Acculturation | |
| Low vs high | 2.75 (1.24, 6.07) |
| Medium vs High | 1.06 (0.51, 2.22) |
| Women vs men | 1.55 (0.94, 2.57) |
| Somali vs Bantu | 0.47 (0.22, 1.01) |
| Dental insurance | |
| Medicaid/government/HMO vs none | 0.53 (0.25, 1.13) |
| Private vs none | 0.96 (0.30, 3.07) |
| SF-12: PCS | 0.94 (0.91, 0.98) |
Note. AOR = adjusted odds ratio; CI = confidence interval; HMO = health maintenance organization; PCS = Physical Component Summary Scale of the Medical Outcomes Study Short-Form 12-item survey; SF = Medical Outcomes Study Short-Form 12-item survey; STOFHLA = Short Test of Functional Health Literacy in Adults. The sample size was n = 439.
Low = 0–22; high = 23–36.
Bivariate analysis showed no significant association between health literacy and periodontal disease. We found periodontal disease in about 6.3% of the high-literacy group and about 6.5% of the low-literacy group (P = .999). In adjusted analyses, participants with low STOFHLA scores had 0.22 the odds of periodontal disease as those with higher STOFHLA scores (P = .047). In this model, those with low levels of acculturation had 11.2 times the probability of periodontal disease as those with high acculturation (P = .01), and those with medium acculturation had 6.3 times the probability of periodontal disease as those with high acculturation (P = .02; Table 5).
TABLE 5—
Association Between Periodontal Disease and Health Literacy Score After Control for Acculturation and Other Factors Among a Somali Refugee Sample in Massachusetts
| Characteristic | AOR (95% CI) |
| STOFHLA score: low vs higha | 0.22 (0.05, 0.98) |
| Acculturation | |
| Low vs high | 11.19 (1.73, 72.28) |
| Medium vs high | 6.33 (1.38, 29.02) |
| Women vs men | 0.33 (0.12, 0.86) |
| Education | |
| None vs ≥ high school | 1.40 (0.33, 5.87) |
| < High school vs ≥ high school | 0.32 (0.08, 1.30) |
| Years in US: 0–4 vs 5–10 | 0.52 (0.22, 1.24) |
| Treatment in past y: yes vs no | 0.23 (0.04, 1.18) |
| Brush teeth: yes vs no | 0.34 (0.14, 0.82) |
| QLM | 4.44 (1.43, 13.77) |
Note. AOR = adjusted odds ratio; CI = confidence interval; STOFHLA = Short Test of Functional Health Literacy in Adults; QLM = Oral Health Quality of Life Measure. The sample size was n = 439.
Low = 0–22; high = 23–36.
DISCUSSION
Overall, our Somali refugee sample had a very positive oral health profile, with a mean number of DMFT of 5.5. For comparison, the mean number of DMFT in the general US adult population is nearly double that of the Somali sample at 10.3.33 US prevalence of periodontal disease is 8.5%, more than 30% higher than the 6.5% prevalence of our Somali sample.34 Refugee dental status was notably worse only for decayed teeth, with a mean of 1.4 among Somalis and 0.8 in the US population,33 a finding that most likely reflects untreated decay near to arrival in the United States. In addition to the favorable examination findings, nearly the entire sample, 98%, reported daily tooth brushing, and almost 75% reported brushing at least twice daily.
Our main hypothesis, that Somalis with higher health literacy levels would have better clinical oral examination findings independent of acculturation levels, was only partially confirmed. In one respect, study findings indicated the opposite: for individuals who had lived in the United States less than 5 years, low health literacy as measured by STOFHLA was associated with better oral examination findings (i.e., lower DMFT). This association was independent of a range of potential confounders, including acculturation level (Table 3).
Because few people saw dentists while in Somalia, Kenya, or Ethiopia, lower lifetime history of caries disease among those with limited or no English ability (as well as low acculturation level) shortly after arrival in the United States may indicate that those individuals benefited from relatively less exposure to—and active avoidance of—refined sugar overseas. Past research has shown that non-Western diets have a protective influence on oral health.35 Individuals who had good health literacy (and general literacy in English) when they arrived in the United States were more likely to have lived in cities overseas, particularly Nairobi, and qualitative interviews suggested that refugees with urban origins consumed more refined sugar overseas than did refugees from rural areas or refugee camps. Finally, high levels of fluoride have been documented as naturally occurring in the water supply of parts of East Africa.36,37
After participants had lived in the United States for 5 years or more, the relationship between STOFHLA scores and lifetime history of disease reversed, with lower literacy associated with increased mean DMFT score, as we predicted. At 5 or more years in the United States, refugees with higher literacy may have been more likely to pursue and gain access to preventive dental care and also to discern which foods are good for oral health and which are not. Alternatively, those with low health literacy may have been more likely to adopt dietary patterns that are deleterious to oral health and less likely to pursue or access preventive care. Qualitative findings confirmed that participants with low literacy and acculturation were not as connected to care or simply may have reacted differently to symptoms of decay. Qualitative interviews also indicated that participants in the United States for less than 5 years were much less likely to be able to access care, so if they had acute decay on arrival in the United States or soon after, they may have been more likely to forgo treatment. By contrast to DMFT scores, the proportion of untreated carious teeth did not differ significantly by literacy level when we controlled for other factors; however, the trend in the relationship between DT/(DT + DFT) and STOFHLA supported the hypothesis for those who had been in the United States less than 5 years.
Although we expected that refugees with low and high acculturation would have better overall oral health than did those with medium acculturation, our results were more complex and did not correspond to the U-shaped relationship with oral health previously reported in the Haitian refugee population.15 Somalis with relatively higher acculturation levels reported in qualitative interviews that they assigned a relatively lower level of importance to regular preventive dental visits than to other, more pressing concerns. However, higher levels of acculturation were also associated with better access to care. Consequently, participants with greater acculturation were less likely than those with less acculturation to have untreated active decay. However, we found much less acculturation overall than expected.
Most participants identified themselves culturally and linguistically as Somali and had very low levels of English literacy, spoken English proficiency, and formal education. These refugees also had very low economic status but relatively low rates of lifetime history of oral disease, possibly reflecting both good oral hygiene practices, such as use of the stick brush, and, at least for the first few years after arrival in the United States, diets low in refined sugar. These practices could be proxies for a myriad of other habits that ultimately may derive from devout practice of Islamic faith in this community, as was suggested in qualitative interviews.
The difference between ethnic Somalis and Somali Bantus may highlight the importance of diet in lifetime history of disease in this population as well as the role of traditional cultural factors. Bantu refugees are a minority ethnic group who lived in southern Somalia and typically followed a traditional, agrarian lifestyle. Caught in the crossfire of civil war, many displaced Somali Bantus remained in refugee camps for extended periods, and few had formal education. Even in the United States, these refugees are often on the margins of the Somali community and are likely to acculturate at an even slower rate than do ethnic Somalis. As might be expected, then, Bantus consumed virtually no refined sugar before they arrived in the United States and adhered to traditional dietary and cultural practices. Our qualitative findings suggested that Bantus continued to be much less likely than ethnic Somalis to consume refined sugar in the United States.
Limitations
Although our sample was robust, a convenience sample is not necessarily representative of the larger community. With respect to age and gender, the sample appeared to be similar to the overall cohort of Somalis in Massachusetts since 1995. The Somali research staff made some effort to recruit participants on weekends, but Somalis who worked during the day were presumably underrepresented, and those who worked nights or weekends or were unemployed were overrepresented.
English literacy and spoken proficiency may have been underestimated. Several participants suspected to have limited English literacy and spoken ability declined the literacy assessment and insisted that they could not read any English at all. In reality, those participants likely would have scored higher than zero. By contrast, we suspected general reporting bias toward responses that would be viewed more favorably. For example, virtually no participants reported cigarette smoking or symptoms of depression, findings that do not match practical experiences with the larger Somali community and do not seem to be attributable to sampling bias. The lack of depressive symptoms reported by our sample also contradicts previously published research with Somalis living in Minnesota.38
All of our results must be viewed cautiously in light of the significant cultural and linguistic challenges encountered. When possible, we used validated instruments with strict instructions to research staff on their nonbiased administration. These instruments were not necessarily ideally transferable to the Somali community; however, development and validation of instruments solely for our study were not feasible. In particular, it should be noted that the revised Haitian Acculturation Scale was not designed or validated for the Somali population, and the Somali community may manifest acculturation in domains not measured by an instrument that was developed for Southeast Asian and Haitian populations. However, we pilot tested this instrument, providing some assurance that it would be appropriate for the Somali community.
Conclusions
The oral health status of Somali refugees is very good. English health literacy and acculturation had unexpected and complex associations with oral health outcomes. Somalis with lower health literacy had a reduced risk of DMFT initially but then had an increased risk at 5 years after arrival in the United States. By contrast, low health literacy had the opposite relationship with untreated decay over time in the United States. Participants’ reports of family resources and knowledge of oral hygiene highlight the significant health assets present in the community; such factors may mitigate the potential impact of health literacy and acculturation on health status. This was illustrated by the overwhelmingly favorable reception of the study by Somalis and their great interest in study findings presented at community meetings.
However, relatively higher levels of acute decay may indicate a future problem, because decay was not necessarily identified early or treated. As Somalis adopt less favorable dietary practices over time in the United States, oral health promotion and prevention for Somali immigrants should highlight the importance of a diet low in refined sugar, frequent brushing, retention of beneficial traditional practices such as use of the stick brush, linkages with cleanliness rituals before prayer, and the importance of preventive visits to the dentist.
Acknowledgments
This study was funded by the National Institute of Dental and Craniofacial Research (P. L. G., PI; grant 1R01DE017716-01A2).
Study findings were presented in part at the Health Literacy Annual Research Conference, October 17, 2011.
We thank our Somali study staff, Fadumo Egal and Ahmed Hassan, for their efforts in making this project successful and also the Somali community of eastern Massachusetts for its enthusiastic embrace of the study.
Human Participant Protection
The study was approved and monitored by the institutional review board of the Massachusetts Department of Public Health.
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