Soda Consumption Among Methamphetamine Users in the U.S.: Impact on Oral Health

Abstract

Purpose

Dental disease is associated with methamphetamine (MA) use, and partly attributed to excessive consumption of sugared sodas. Hence the purpose was to verify patterns of sugared soda intake and their relationship to oral health.

Methods

Detailed assessments with 541 MA users at two dental clinics were conducted. Assessment included a lifetime history of methamphetamine use, sugared soda consumption, and a dental exam.

Results

Subjects were predominantly male (80.8%; mean age 44.4 years), on average had used MA for 11.6 years, and drank an average of 35.3 sodas per month. Number of days of MA use over the past 30 days was significantly associated with soda consumption. Increased years of MA use was associated with the likelihood of users reporting less overall satisfaction with life because of their teeth, specifically difficulty eating, and dry mouth. This is the first study to show a statistically significant association between MA use and sugared soda consumption.

Conclusions

MA users’ consumption of sugared sodas is higher than the adult general population, and this is the first study to show a statistically significant association between MA use and sugared soda consumption. In addition, increased soda consumption was associated with more dental problems among MA users.

Introduction

Consumption of soft drinks has increased in the U.S. among adults over the past few decades (Enns et al., 1997; National Soft Drink Association, 2004). Centers for Disease Control (CDC) data from the National Health and Nutrition Examination Survey (NHANES) indicates one-half of the U.S. population consume sugared drinks on any given day, and 25% consume more than one 12-ounce can of soda (Ogden et al., 2011). The American Heart Association recommends consumption of fewer than three 12-ounce cans of carbonated soda per week (Lloyd-Jones et al., 2010).

Consumption of sugared sodas has been linked to negative health consequences, including weight gain, decreased bone density, headaches, anxiety and loss of sleep (Tahmassebi et al., 2006; Whiting et al., 2001), and also may be an important factor in dental decay (Bartlett et al., 2003; Heller et al., 2001; von Fraunhofer and Rogers, 2004). The underlying acidity is believed to be a factor in dental erosion, as most soft drinks contain one or more food acidulants. In addition, the sugars are metabolized by plaque microorganisms to generate organic acids that bring about demineralization leading to dental caries (Tahmassebi et al., 2006).

The Link Between Soft Drink Consumption & Methamphetamine Use

Methamphetamine (MA) is a highly addictive psychostimulant; it has become one of the fastest growing drug problems in the U.S (NIDA, 2002; SAMHSA, 2006). It has replaced crack cocaine and marijuana as the drug of choice (Rawson, 2002). Over 12 million Americans have tried MA at least once, with the majority of users age 18 – 34 (SAMHSA, 2004).

Of the various health effects associated with MA use, rampant dental disease is a distinctive finding, leading the American Dental Association to identify it as a serious dental health issue (American Dental Association, 2007). Postulated mechanisms of MA-associated dental disease include: (1) xerostomia, or dry mouth, produced by a central inhibition of salivatory nuclei via stimulation of alpha-2 receptors in the brain; (2) a general state of dehydration that leads to frequent consumption of soft drinks; and (3) little or no attention to oral hygiene (Klasser and Epstein, 2005). In terms of the first factor, xerostomia, decreased salivary flow rate due either to a central inhibitory action of MA or generalized dehydration could contribute to the increased occurrence of dental caries (Saini et al., 2005). In terms of the second factor, MA users report craving sugar and typically drink large quantities of soft drinks (Donaldson and Goodchild, 2006). One study found a patient with a seven-year history of MA use reported dry mouth, and consequently imbibed two liters per day of carbonated beverages (Shaner et al., 2006). Donaldson and Goodchild (2006) report a patient who consumed approximately twelve 16-ounce soft drinks per day. Among a sample of 18 MA users, Morio et al. (2008) found users were more likely than controls to consume sugared soda. However, variability in serving sizes resulted in differences in daily intakes that approached but did not achieve statistical significance. The oral health problems of those who use MA and who consume soda in excess have been found to demonstrate similar clinical features, and the ingredients used in preparing MA can include extremely corrosive, acidic materials such as battery acid (Bassiouny, 2013). Finally, in terms of the third factor, some patients have reported not practicing oral hygiene during times of heavy drug use (Donaldson and Goodchild, 2006; Morio et al., 2008).

Consequences of Methamphetamine Use on Dental Outcomes

Previously, we utilized the Methamphetamine Treatment Project (Huber et al., 2000), one of the largest randomized clinical trials of treatment for MA dependence, to substantiate dental effects of MA use (Shetty et al., 2010). Dental disease was prominent among MA users (41.3%). Despite the relatively young age of the sample (mean age = 36.5 years), users had significantly more missing teeth than did matched National Health and Nutrition Examination Survey (NHANES III) participants; almost 60% had one or more missing teeth (excluding third molars); mean # of teeth missing was 4.58; and 13.3% were already wearing dentures (partial or complete).

Purpose of the Current Study

This study utilizes data from a project funded by the National Institute of Drug Abuse designed to validate rates and patterns of dental caries and oral disease among MA users (both HIV-negative and HIV-positive). Among MA users, exploratory and descriptive analyses were conducted to determine: (1) the average soft drink consumption per day among MA users; (2) whether heavier use of MA was associated with more soft drink consumption; and (3) whether higher soft drink consumption was associated with more self-report of dental problems. This is the largest study of MA users to investigate the association of MA use and sugared soft drink consumption, and dental problems.

Method

Study Eligibility

Assessments were conducted on 541 MA-using individuals at two community dental clinics in Los Angeles County. Subject inclusion criteria included being age 18 or older; use of MA in the past 30 days; physically able to complete the dental exam, psychosocial assessment, and provide a urine sample; provision of signed written informed consent; and English or Spanish speaking.

Procedures

IRB-approved flyers and matchbooks with study information were distributed at bars, restaurants, convenience stores, and other locations in the Los Angeles area. The first community site was AIDS Project Los Angeles (APLA) Dental Services, Inc., which provides comprehensive dental services to people living with HIV/AIDS throughout L.A. County. The original clinic opened in 1985 as the nation’s first dental facility totally dedicated to serving persons living with HIV/AIDS. HIV-negative methamphetamine users were also seen for assessments at this site. The second site was Mission Community Hospital-UCLA Dental Center (MCH) located in the San Fernando Valley within the Los Angeles metropolitan area, a public clinic that provides general dentistry on a sliding scale based on patient’s income. Written consent from eligible subjects was obtained by trained research staff using procedures approved by the Institutional Review Board at the University of California, Los Angeles.

The face-to-face psychosocial interview was approximately one hour in length, followed by the dental exam. (Only data from the psychosocial assessment were used in the analyses for this paper.) The interview was conducted by a trained bilingual interviewer, in the language (English or Spanish), chosen by the participant. Participants were paid $60 in gift cards upon completion of assessments.

Measures

Dental Health

The National Health and Nutrition Examination Survey (NHANES)(CDC, 2012) was utilized to determine whether subjects had dental extractions in the past year and perception of the current condition of their teeth. It assesses overall health and nutrition status of adults in the United States, examining a nationally representative sample of approximately 5,000 people each year.

Oral Health

The Oral Health Impact Profile (Slade and Spencer, 1994) is a 14-item scale that assesses subjects’ perceptions of the effect their dental health has had on their well-being and pain over the past 30 days. Additionally, the Adult Dental Health Questionnaire (Office for National Statistics, 1998) surveyed dental health, dental care, and access to dental services.

Xerostomia

Dry mouth was surveyed using the NHANES xerostomia question: “Does the amount of saliva in your mouth seem to be too little, too much, or you don’t notice it?”

HIV Status

Subjects were asked if they had ever had an HIV test, and if so, if they were HIV-positive.

Substance Use

The Natural History Interview (NHI) (McGlothlin et al., 1977; Nurco et al., 1975) was used to assess history of and current use of MA, and treatment. Participants were asked age of first use, number of years use, primary method of use, how many days in the past 30 days they had used, and how many times they had been treated for MA use. The NHI has been administered to thousands of substance users and collects sequential, longitudinal data on patterns of drug use, utilizing significant life events as cues for recall.

Soda Consumption

Questions from the 24-hour dietary recall interview (NHANES III dietary intake data) (CDC, 2012) were used to assess consumption of sodas containing sugar (i.e., how often they had consumed specific beverages per day, week, or month, and average size of the drinks as small, medium, or large).

Data Analysis

Data analysis was performed using SAS 9.2 software. Simple and multiple linear regressions were used to determine associations between the continuously scaled variables of interest. Binary outcomes were modeled as functions of predictors using logistic regression. The natural log of one plus the number of medium sugary sodas was taken to scale the number of sodas in analysis. In order to adjust for age in regression models without being collinear to lifetime meth use, the ratio of number of years of MA use to number of adult years of life (age minus 18) is calculated and used as a variable.

Results

Subject characteristics are presented in Table 1. Subjects were predominantly male (81%), with an average age of 44.4 (SD = 9.5; range 19 – 70 years). Average age at time of first MA use was 28.4 (SD = 10.5; range 12 – 65 years), with the average number of calendar years of MA use being 11.6 (SD = 8.4; range 1 – 47).(Five subjects were missing data on lifetime methamphetamine use) Racial makeup of the participants was largely Non-Hispanic African-American (42.1%), with the remainder primarily Hispanic (30.5%), or Non-Hispanic White (20.0%). The sample was 74.1% HIV-negative and 25.9% HIV-positive.

Table 1.

Characteristics of the sample (n = 541)

	N	%
Sex
Male	437	80.78%
Female	104	19.22%
Race or Ethnicity
White	108	19.96%
African-American	228	42.14%
Asian	3	0.55%
Hispanic	165	30.50%
Other	37	6.84%
Marital Status
Married/Living as Married	38	7.02%
Widowed, Divorced, or Separated	115	21.26%
Never Married	388	71.72%
Education
Did not graduate high school	165	28.84%
High school graduate/GED	194	35.86%
Some college (no degree)	134	24.77%
Associate degree	18	3.33%
Bachelor’s degree or higher	39	7.21%
HIV Status
Positive	140	25.88%
Negative	401	74.12%
Age Range
18–30 years old	53	9.80%
31–40 years old	113	20.89%
41–50 years old	218	40.30%
51–60 years old	141	26.06%
>= 61 years old	16	2.96%
Frequency of Use
Low (1–9 days in last 30)	253	46.77%
Medium (10–15 days in last 30)	166	30.68%
High (16–30 days in last 30)	122	22.55%

	M (SD)	Min, Max
Days of MA use in the last 30 days	10.2 (7.4)	1, 30
Number of medium sodas consumed in the last 30 days (n=540)	35.3 (64.8)	0, 640
Calendar years of MA use (n=536)	11.6 (8.4)	1, 47

Table 1 shows the summary information for soda consumption and methamphetamine use. The average number of medium sodas containing sugar consumed in the last 30 days was 35.3 (SD = 65.8). (One subject had missing values for questions related to sugary soda consumption, thus the sample size for number of sodas consumed in the last 30 days is 540 instead of 541.) Four subjects reported drinking large quantities of sugary sodas in the last 30 days (400, 480, 570, and 640) while many subjects reported no sugary soda consumption, thus regression analysis was conducted on the log-transformed number of sodas plus one. The number of days of MA use, over the past 30 days, was significantly associated with soda consumption, as seen in Table 2. Each day of methamphetamine use in the last 30 days was associated an increase in the geometric mean of sodas consumed by 2.2% (p = 0.016). This association was significant even when the analysis was restricted, deleting the four potential outliers with very high consumption. When this regression was performed using the log transformed number of days of MA use in the last 30 days, the association was still significant with a simpler interpretation: a 1% increase in the number of days of MA use was associated with a 0.20% increase in one plus the number of medium sugary sodas in the last 30 days (p=0.007).

Table 2.

Linear and logistic regression coefficients by outcomes and predictors

	Regression
	Days of MA Use in Last 30 Days		Number of Calendar Years of MA Use		Percent of Years of Adulthood using MA after Adjusting for Age
	Parameter Estimate (SE)	p	Parameter Estimate (SE)	p	Parameter Estimate (SE)	p
Log (Number of medium sugary sodas in last 30 days +1)	0.025 (0.010)	0.013*	−0.012 (0.0088)	0.17	−0.05 (0.27)	0.86
Tooth extracted in last year	0.0039 (0.014)	0.78	0.0056 (0.012)	0.64	−0.17 (0.38)	0.66
Condition of gums as “excellent” or “very good”	−0.023 (0.014)	0.12	−0.028 (0.013)	0.037*	−0.49 (0.39)	0.20
“Very often” or “often” believe that quality of life is lower due to teeth/gums	0.0025 (0.014)	0.86	0.037 (0.01)	0.0012**	0.95 (0.37)	0.0092**
“Very often” or “often” feel self-conscious because of teeth	0.020 (0.012)	0.098+	0.030 (0.011)	0.0044**	0.69 (0.32)	0.033*
Reporting “too little” saliva	0.0021 (0.014)	0.88	0.032 (0.01)	0.0057**	0.74 (0.37)	0.048*
“Very often” or “often” have difficulty eating due to teeth	0.019 (0.012)	0.12	0.018 (0.011)+	0.085+	0.44 (0.33)	0.18

Note: Hypothesis tests were considered significant for two-sided p < 0.05. Controls on the familywise error rate, such as the Bonferroni correction, were considered but not used for this study because each of the hypothesis tests are not necessarily independent.

⁺0.05<p<0.1,

^*p <0.05,

^**p<0.01

Those who drank more soda in the last 30 days were less likely to have had a tooth extracted in the last year, although this association did not reach significance (p = 0.079). Soda consumption was not found to be significantly associated with any of the other dental health outcomes.

The likelihood of subjects reporting the condition of their gums as excellent or very good was associated with the number of years of MA use (p = 0.037): for each additional year of MA use, the likelihood of excellent or very good status decreases by 2.7% (OR = 0.973, 95% CI [0.948, 0.998]). However, after adjusting for the age of the participants and using the ratio of years of use to years of adulthood, this association was no longer present. Additional years of MA use were also related to an increase in likelihood of reporting “often” or “very often” that life is less satisfying because of their teeth (p = 0.0012, OR = 1.038, 95% CI [1.015, 1.061]) and an increase in the probability participants reporting “often or “very often” feeling self-conscious or embarrassed as a result of their teeth (p = 0.0044, OR = 1.03, 95% CI [1.009, 1.052]), and these effects were still pronounced after adjusting for age. Subjects who used MA over more years were also more likely to indicate that they have “too little” saliva in their mouth as opposed to “too much” or “did not notice:” for each additional year of use, the likelihood of reporting dry mouth increased 3% (OR=1.03, p=0.0057, 95% CI [1.01, 1.06]).

There were no significant differences between sugary soda consumption between MA users who were HIV positive versus HIV negative. However, HIV-positive MA users were 80% more likely to have a tooth extracted in the last year compared to HIV-negative MA users (p=0.0084, OR=1.80, 95% CI [1.16, 2.80]), and nearly twice as likely to report having “too little” saliva (p=0.0017, OR = 2.00, 95% CI [1.30, 3.07]). No significant relationship between HIV and any of the other dental health outcomes was found. Table 3 shows the regression parameter estimates when HIV is included in the age-adjusted models with proportion of adult lifetime MA use, and the inclusion of HIV in the model does not change the associations of age and adult lifetime MA use with the dental health outcomes.

Table 3.

Regression parameter estimates when HIV is included in model with age and percent of adult years using MA

	Estimate (SE)	p
Log (Number of medium sugary sodas in last 30 days +1)
Age	−0.021 (0.0081)	0.0086**
Percent of Adult Years of MA Use	−0.002 (0.27)	0.99
HIV	0.25 (0.17)	0.14
Tooth extracted in last year
Age	0.033 (0.012)	0.0066**
Percent of Adult Years of MA Use	−0.06 (0.39)	0.88
HIV	0.54 (0.23)	0.019*
Condition of gums as “excellent” or “very good”
Age	−0.036 (0.012)	0.0016**
Percent of Adult Years of MA Use	−0.49 (0.39)	0.20
HIV	−0.004 (0.24)	0.98
“Very often” or “often” believe that quality of life is lower due to teeth/gums
Age	0.040 (0.012)	0.0006***
Percent of Adult Years of MA Use	0.95 (0.37)	0.010*
HIV	−0.033 (0.24)	0.89
“Very often” or “often” feel self-conscious because of teeth
Age	0.030 (0.010)	0.0024**
Percent of Adult Years of MA Use	0.71 (0.33)	0.030*
HIV	0.11 (0.20)	0.60
Reporting “too little” saliva
Age	0.044 (0.012)	0.0003***
Percent of Adult Years of MA Use	0.91 (0.38)	0.018*
HIV	0.72 (0.23)	0.0015**
“Very often” or “often” have difficulty eating due to teeth
Age	0.014 (0.010)	0.17
Percent of Adult Years of MA Use	0.50 (0.33)	0.13
HIV	0.30 (0.20)	0.15

⁺0.05<p<0.1,

^*p <0.05,

^**p<0.01,

^***p<0.0001

Discussion

The current study had three goals: determining the average soft drink consumption per day among MA users; investigating whether heavier use of MA was associated with more soft drink consumption; and exploring whether higher soft drink consumption was associated with more self-report of dental problems. We found that MA users consumed, on average, 35.3 sodas per month. This is much higher than the American Heart Association recommendation of < 3 cans per week, in fact, it is more than three times that recommendation. The consumption of soft drinks has increased tremendously (Shenkin et al., 2003), and a positive relationship between cumulative caries scores and the frequency of use of carbonated beverages has been long established (Ismail et al., 1984). Utilizing the California Health Interview Survey (CHIS)(UCLA Center for Health Policy Research, 2012)—the same state from which the current sample of MA users was drawn—it is clear that MA users’ consumption of sugared sodas is higher than the adult general population. Data from the CHIS show that 40% of adults report not drinking soda at all; 36% occasionally but not every day; and slightly less than one out of four adults (24%, or 6.4 million California adults) drink at least one soda every day. (This is similar to other cities’ data, for example one in four adult New York City residents consume one or more cans of sugared soda per day [Rehm et al., 2008], and this was defined as frequent consumption.) Of our MA users, 32.2% drank two or more sodas per day; 37.6% indicated they consumed 30 or more medium sugary sodas in the previous 30 days. The consumption patterns in our group of MA users corresponds closely to the subset of the general population group that has the highest consumption--specifically, teenagers/young adults. According to CHIS data, youth have an average of 0.99 servings per day of sugared soda on 24 hour recall measures, and 1.21 according to the Food Frequency Questionnaire (Heller et al., 2001)--with significant associations between the numbers of decayed, missing, and filled permanent tooth surfaces (DMFS) and soda consumption generally seen in persons over age 25. Adolescents in the U.S. have been steadily increasing their consumption (Wang et al., 2008). National data shows that the most eager users are 12 to 29 year old males, who drink soda have an average of slightly more than 2 sodas per day, providing 44% of their refined sugars a day from soft drinks (Jacobson, 2005).

As for the question of whether heavier MA use is associated with higher consumption of sugared sodas, this study is the first to show a statistically significant association between MA use and sugared soda consumption. While there have been very good and illustrative anecdotal reports, as well as one study reporting a trend for this association, our investigation is the first to document a statistically significant association in a large sample of methamphetamine users.

This study revealed that increased soda consumption was associated with more self-reported dental problems among MA users. HIV-positive MA users were 80% more likely to have had a toot extracted in the past year. For all MA users, both HIV-negative and HIV-positive users, the quality of life in terms of oral health appears to be strongly related to length of MA use. As years of use increased, MA users were more likely to report less satisfaction with life due to their teeth. In addition, longer use was associated with report of feeling more self-conscious because of their teeth. There was also a trend for longer use to be associated with report of self-image problems and a greater likelihood of xerostomia.

Our study had several limitations. We only obtained information on recent soda consumption; lifetime dietary habits would have provided longitudinal information. In addition, this was a cross-sectional design. Finally, findings are reliant on self-reported information (i.e., methamphetamine use, soda consumption, dental problems). Offsetting strengths included use of measures that have been well validated and proven reliable, and availability of the largest sample to MA users to date.

In summary, this large sample of MA users had a higher consumption of sugared sodas than the general population, and this is the first study to document that there is a statistically significant association between MA use and sugared soda consumption. Increased soda consumption is associated among MA users with more reported dental problems. Thus, MA users are at a high risk for dental disease due to their MA use, their soda consumption, and any interaction of these two factors. Correspondingly, management of dental disease in MA users needs to expand beyond the conventional focus on correcting the damaging effects of caries to include consideration of other variables that influence long-term outcomes. The frequency of sugared sodas coupled with any MA-induced xerostomia and diminished oral hygiene increases both existing and future caries risk. Thus, questioning MA users about their soda consumption should be a component of the initial consult, and the information used to establish the patient risk profile. The management of dental disease in MA users could include behavioral modifications that encourage substituting alternate beverages (e.g., water instead of sodas), aggressive caries reduction programs that involve fluoride products and chlorhexidine mouthwashes (McFarland and Fung, 2011), and stimulating saliva flow through medications or the use of sugarless chewing gums (Goodchild et al., 2007). Understanding risk factors unique to MA-users provides opportunities for specific preventive measures that will diminish the attendant dental morbidity.