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Traits of Persons Who Drink Decaffeinated Coffee
Traits of Persons Who Drink Decaffeinated Coffee AI KUBO SHLONSKY, MPH, ARTHUR L. KLATSKY, MD, AND MARY ANNE ARMSTRONG, MA
PURPOSE: Little is known about the traits of decaffeinated coffee drinkers, who are sometimes used to ascertain whether the health effects of coffee intake are due to caffeine or some other coffee ingredient. METHODS: We studied these traits in 12,467 persons who reported type of coffee consumed at health examinations; 36% drank caffeinated only, 13% drank decaffeinated only, 27% drank both types and 24% drank no coffee. RESULTS: Odds ratios estimated from logistic regression analyses revealed that compared with regular (caffeinated) coffee drinkers or abstainers, decaffeinated coffee drinkers were less likely to be heavy coffee drinkers, smokers, alcohol drinkers, users of caffeinated soft drinks and medication and to be free of illness. Increased decaffeinated coffee drinking was associated with older age, female sex, African American ethnicity, use of special diets and cardiovascular, gastrointestinal, or neuropsychiatric symptoms. Persons on special diets were more likely to drink decaffeinated coffee whether they had heart disease or were free of any illness. CONCLUSION: These data suggest that decaffeinated coffee use is related to illness in some persons but to a healthy lifestyle in others. These potential and possibly conflicting confounding factors need to be considered when studying the health effects of coffee or caffeine. Ann Epidemiol 2003;13:273–279. © 2003 Elsevier Science Inc. All rights reserved. KEY WORDS:
Caffeine, Coffee, Decaffeinated Coffee, Risk Factors, Epidemiology.
INTRODUCTION Although caffeine is believed to be the most widely consumed and studied drug in history (1), most questions regarding its health effects remain unanswered (2, 3). Research results are inconclusive about both adverse and beneficial relations of caffeine to several health outcomes. Possible adverse relations include those to coronary heart disease (4), fibrocystic breast disease (2, 3), several types of cancer, (5), and reproductive health effects (6). Possible beneficial relations include reduced risk of suicide (7) or liver cirrhosis (8). No overall effect on mortality has been found (7, 9). Yet, due to the high prevalence of its use, even small health effects of caffeine might cause a substantial public health impact. Approximately 80% of Americans consume coffee, and among coffee drinkers the average US consumption is 3.1 cups of coffee per day (10). Coffee drinking is sometimes considered a marker for caffeine intake, and caffeine’s stimulatory property makes it the most obvious and most studied compound in coffee.
From the School of Public Health, University of California, Berkeley, CA (A.K.S.); and the Division of Research, Kaiser Permanente Medical Care Program, Oakland, CA (A.L.K., M.A.A.) Address correspondences to: Arthur L. Klatsky, MD, Kaiser Permanente Medical Center, 280 West MacArthur Boulevard, Oakland, CA 94611, USA. Tel.: (510) 450-2757; Fax: (510) 572-7456. E-mail: alk@dor. kaiser.org Received October 31, 2001; revised March 25, 2002; accepted May 3, 2002. © 2003 Elsevier Science Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010
Although coffee contains hundreds of other potentially biologically active compounds (11), caffeine is often automatically singled out as the culprit of negative health outcomes. The studies of coffee and health must also take into account that coffee use is associated with smoking, alcohol consumption, less physical exercise, and unhealthy dietary habits (4–5, 8–9). Relationships between decaffeinated coffee use and health are sometimes used as an indicator of whether apparent coffee effects are likely due to caffeine or some other coffee ingredients. Little is known, however, about differential relations of potential confounders to regular or decaffeinated coffee use. It is possible that any apparent disparities in disease outcomes between caffeinated and decaffeinated drinkers are due to differences in life-styles or medical history between the two groups, rather than to the effect of caffeine. To supplement the limited available data, we explored the associations between type of coffee consumed to demographics, medical history, current health status, and lifestyle habits for a multi-ethnic sample of 12,467 persons.
SUBJECTS AND METHODS Study Population and Data The study protocols were approved by the Institutional Review Board of the Kaiser Permanente Medical Care Program. Subjects were 12,467 persons who supplied data 1047-2797/03/$–see front matter PII S1047-2797(02)00414-3
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Selected Abbreviations and Acronyms CI confidence interval MHC multiphasic health checkup OR odds ratio
about the type of coffee they drank at health examinations in 1984–1985. The examination, known as a Multiphasic Health Checkup (MHC), was offered for decades at the Oakland and San Francisco facilities of a large Northern California prepaid health care organization (12). Examinees voluntarily provided information during this routine health examination. Subjects represented a reasonable cross-section of the population in the area served (13), although “health conscious” persons were probably somewhat over-represented and the medically indigent were underrepresented. Subjects supplied demographic data, medical history information, and data about alcohol use, smoking, and total number of cups of coffee drunk per day on other questionnaires at the MHC. The questionnaires included queries about (i) reason for taking the examination; (ii) current symptoms, problems, and treatments; (iii) past diagnoses, surgical operations, and risk factors; and (iv) psycho-social problems. Health measurements and laboratory tests were done, which included height, weight, systolic and diastolic blood pressure, hemoglobin, leukocyte count, creatinine, glucose, and total cholesterol levels. A supplementary questionnaire was offered at the end of the examination, and coffee type query was answered by 71% (12,467/17,680) of all examinees. Most of this disparity was due to absences of the special research clerk during which no supplementary forms were distributed. A smaller proportion declined the supplement, the precise number is not known. Distributions of demographic and outcome variables in these subjects were very similar to those of all 17,680 MHC examinees in the years involved. The coffee type query was “If you drink coffee, what type do you drink?”, with these options: “regular (caffeinated) coffee only”, “decaffeinated coffee only”, “both regular and decaffeinated coffee”, and “never or almost never drink coffee.” Subjects (n 369) who checked “never or almost never” on the coffee type query but stated an amount of coffee elsewhere were excluded from analyses; (83% of these stated 1 cup per day). Analytic Methods Simple cross-classifications were done to examine demographic differences. Statistical analyses were performed using SAS for Windows (version 8.1) statistical software package (SAS Institute Inc., Cary, NC). For analyses presented here, exclusive use of decaffeinated coffee was the study end point.
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Multivariate logistic regressions, yielding odds ratios from coefficients, were performed to estimate the relations between decaffeinated coffee use and items of interest. The items included: (i) health measurements; (ii) each of the 30 queries regarding medical history (“has a doctor ever said you have . . . ?”); (iii) each of the 46 current symptoms queries (“do you now have . . . ?”); (iv) queries about special diets (low salt, low fat, low calorie, vegetarian); (v) and recreational physical activity. Composite variables were constructed for (i) possible cardiovascular disease-related items (one or more “yes” to: now have heart trouble, heart irregularity, palpitations, or high blood pressure; ever had heart disease, stroke, arrhythmia, or hypertension; currently taking medications for heart disease: n 3244); (ii) possible gastrointestinal disease-related items (now have trouble swallowing, diarrhea, constipation, stomach pain, or liver trouble; ever had liver or colon/bowel disease: n 3345); and (iii) high intensity recreational physical activities ( once/week swimming, jogging/running, outdoor bicycling, stationary bicycling, calisthenics, exercise class, gym workouts, or tennis: n 5220). For each query, two separate regressions were done to estimate the likelihood of decaffeinated coffee use compared with (i) users of regular coffee only or (ii) nondrinkers of coffee. The reference groups were persons who answered “no” to the respective queries. Thus, no comparisons were made for persons who drank both caffeinated and decaffeinated coffee. All models were adjusted for; age (continuous), race (white as referent, black, others), sex (female as referent), smoking status (never as referent, ex-smoker, 1pack/ day, 1/day), usual alcohol intake (never as referent, exdrinker, 1drink/day, 1 to 2 drinks/day, 3 drinks/day drinkers), and educational attainment (no college as referent, partial college, college graduate), marital status (currently married as referent, formerly married, never married). Amount of coffee intake (4 or 4 cups/day) was also included in the model that compared decaffeinated to caffeinated coffee use.
RESULTS Coffee Type by Demographic Traits and Habits Of the 12,098 persons who supplied valid coffee type data 36% (n 4409) of the subjects that drank caffeinated coffee only, 13% (n 1545) decaffeinated coffee only, 27% (n 3,307) both caffeinated and decaffeinated coffee, and 24% (n 2,837) no coffee (Table 1). Persons drinking four or more cups of coffee a day were less likely to drink decaffeinated coffee only. Prevalence of exclusive decaffeinated coffee use tripled from ages younger than 40 years to age 60 and older and, compared with other categories, was relatively greater among women, blacks, those without college education, non-alcohol drinkers, and
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TABLE 1. Characteristics of study subjects classified by coffee types Traits Number of persons*
Gender Male Female Ethnicity Blacks Whites Others Age 40 40-59 60 Education No college Some college College Marital status Currently married Never married Formerly married Cigarette smoking Never Ex-smoker 1 pack/day 1 pack/day Alcohol Never Ex-drinker 1 drink/day 1-2 drinks/day 3 drinks/day Coffee (cups/day) Never/occasional 4 cups/day 4cups/day Tea (cups/day) Never/occasional 4 cups/day 4cups/day
Total 12098
Regular only 4409
Decaf only 1545
Both 3307
None 2837
N
%*
%*
%*
%*
5230 6868
40.5 33.3
10.4 14.6
26.6 27.9
22.5 24.2
3170 6857 2007
28.3 40.2 36.3
14.4 12.1 12.6
22.2 29.4 28.6
35.1 18.4 22.5
4951 4362 2785
38.0 35.1 35.7
6.8 14.5 20.7
23.2 32.1 27.3
32.0 18.3 16.3
4513 3133 4452
36.5 36.3 36.5
15.4 11.0 11.3
25.4 25.1 30.9
22.7 27.6 21.3
6530 2150 2301
36.3 37.4 34.9
14.1 5.7 15.9
28.7 21.9 29.3
21.0 35.0 19.9
7209 2822 1351 716
32.6 38.6 43.7 52.9
12.5 14.7 12.1 9.4
26.4 30.5 26.3 26.0
28.5 16.2 18.0 11.7
1802 537 6695 2223 841
22.9 31.8 35.7 45.8 49.5
15.4 14.2 12.9 11.5 8.8
20.5 26.1 28.5 30.0 26.6
41.2 27.9 22.9 12.7 15.1
3269 7013 1722
3.2 47.4 56.0
7.3 16.2 8.8
3.9 36.4 35.3
85.6 N/A N/A
6506 5224 246
39.2 33.3 28.1
12.2 13.3 12.2
24.2 31.5 24.8
24.4 21.9 35.0
*The percentage of each row may not sum up to 100% due to rounding and the total N may not add up for some categories due to missing values.
ex-smokers. Decaffeinated use only was less prevalent among never married persons, heavy smokers, and daily alcohol drinkers. More than half of all persons drinking four or more cups of coffee per day drank only regular (caffeinated) coffee. Prevalence of regular coffee drinking was higher in males, whites, current smokers, and daily alcohol drinkers, and little related to age, educational attainment, or marital status. Coffee abstinence was more prevalent among persons who were black, younger than 40 years, and never married, smoked, or consumed alcohol. The characteristics of persons reporting use of both caffeinated and decaffeinated coffee fell between those of the regular and decaffeinated coffee only groups.
Multivariate analyses (Table 2) showed that many relations were independently significant, including inverse associations of decaffeinated coffee use (vs. caffeinated) with current alcohol use, 1 pack or more/day of cigarette smoking, 4 cups or more/day of coffee drinking, and never married status. Age, female sex, and black race showed positive relations. When decaffeinated coffee drinkers were compared with abstainers, independent inverse associations were present for black race, never married status, and partial college education status, while positive associations were found for female sex, current alcohol use and current or past cigarette use (see Table 2). No association was found between any health measurement (hemoglobin, leukocyte count, creatinine, glucose,
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TABLE 2. Adjusted association of traits and demographics with decaffeinated coffee use vs. Regular coffee users Traits Sex Male Female Ethnicity White Black Others Alcohol use Never Ex–drinkers 1drink/day 1–2 drinks/day 3 drinks/day Cigarette smoking Never Ex–smoker Current 1pack/day Current 1pack/day Educational attainment No college Partial college College graduate Marital status Currently married Formerly married Never married Coffee consumption 4 cups/day 4 cups/day
OR*
95% CI
TABLE 3. Medical history and current problem queries related* to decaffeinated coffee use compared to regular (caffeinated) coffee usea
vs. Abstainers OR*
95% CI
1.0 1.6
Ref. 1.4–1.8
1.0 1.9
Ref. 1.6–2.2
1.0 1.6 1.1
Ref. 1.3–1.8 1.0–1.4
1.0 0.8 1.6
Ref. 0.7–1.0 1.3–2.0
1.0 1.0 0.8 0.6 0.5
Ref. 0.7–1.4 0.6–0.9 0.5–0.7 0.3–0.7
1.0 1.3 2.1 2.8 2.0
Ref. 0.9–1.8 1.7–2.5 2.2–3.6 1.4–2.9
1.0 1.1 0.9 0.8
Ref. 0.9–1.3 0.7–1.1 0.6–1.0
1.0 1.6 2.0 2.0
Ref. 1.3–1.9 1.6–2.6 1.4–2.9
1.0 0.9 1.1
Ref. 0.8–1.1 1.0–1.3
1.0 0.7 0.9
Ref. 0.6–0.9 0.8–1.1
1.0 1.0 0.6
Ref. 0.9–1.2 0.5–0.8
1.0 1.0 0.5
Ref. 0.8–1.2 0.4–0.7
1.0 0.4
Ref. 0.3–0.5
N/A N/A
*Odds Ratio estimated by logistic regression adjusted for age, sex, race, education, cigarette smoking, and alcohol consumption.
and total cholesterol) and decaffeinated coffee use (data not shown). However, high cholesterol level (240 mg/dl) was related to total coffee consumption (4 cups/day) (OR 1.2; 95% CI 1.1–1.3), confirming our findings (14) of a total coffee-cholesterol relation in an earlier incomplete dataset in this study population. Medical History, Symptoms, and Decaffeinated Coffee Use A third (6/18) of items showing significant relations to decaffeinated coffee use were related to heart disease (Table 3). Assuming strong inter-item correlation, a cardiovascular disease composite (described earlier) was tested, yielding a decaffeinated/caffeinated odds ratio of 1.5 (95% CI 1.3– 1.7, P 0.001). Similar analyses of decaffeinated coffee users versus abstainers showed that over half (5/9) of the items significantly associated with decaffeinated coffee use was cardiovascular related (Table 4). In this comparison, the odds ratio for the cardiovascular composite was 1.3
Query
N (yes)
Odds ratio
95% CI
Medical history: “Has a doctor ever said you had . . . ?” Heart disease 326 2.4 1.7–3.3 Hiatal hernia 524 1.7 1.3–2.2 Stomach/duodenal ulcer 676 1.6 1.3–2.1 Hypertension 2125 1.4 1.2–1.6 Hospitalization 716 1.3 1.0–1.6 No “yes” responses 2555 0.8 0.7–0.9 Current problems: “Do you now have . . . ?” Heart trouble 326 2.2 1.6–3.0 Psychiatric care 447 1.5 1.2–2.1 Medication for heart 1998 1.5 1.3–1.7 High blood pressure 1683 1.4 1.2–1.6 Difficulty sleeping 1855 1.4 1.2–1.6 Loss of sexual interest 879 1.3 1.1–1.7 Heart irregularity 906 1.3 1.1–1.6 Stomach pain 1033 1.3 1.1–1.6 Back trouble 2305 1.3 1.1–1.5 Severe headache 1590 1.2 1.0–1.5 Trouble with eyes 2105 1.2 1.0–1.4 No “yes” responses 1526 0.8 0.6–0.9
P-value 0.001 0.001 0.001 0.001 0.04 0.02 0.001 0.02 0.001 0.001 0.001 0.01 0.008 0.01 0.003 0.02 0.02 0.006
*Estimated by logistic regression adjusted for age, sex, race, education, cigarette smoking, and alcohol consumption. Table includes all items with p 0.05. (See appendix A for list of items not significantly related). a Drinks only decaffeinated coffee (n 1,545) vs only caffeinated coffee (n 4,409).
(95% CI 1.2–1.6). Therefore, persons with cardiovascular problems are more likely to choose decaffeinated coffee instead of either regular coffee or none. Three gastrointestinal system-related items showed significant relationships for decaffeinated/caffeinated coffee use (see Table 3). These were all related to the upper gastrointestinal area (hiatal hernia, stomach/duodenal ulcer, stomach pain). The odds ratio for the gastrointestinal composite was 1.3 (95% CI 1.1–1.5). No similar gastrointestinal associations were seen for the decaffeinated versus abstainer comparisons. Individuals who did not indicate a single positive response to any of the 30 medical history queries (n 2555) or to any of the 46 current symptoms (n 1526), thus presumably healthy individuals, were significantly less likely to be decaffeinated coffee drinkers. However, these individuals were neither more nor less likely to drink decaffeinated coffee than to be coffee abstainers. A separate analyses showed that those without any current symptoms are slightly more likely to choose regular coffee than none (OR 1.2, P 0.02). These presumably healthy individuals were, thus, less likely to consume decaffeinated coffee or to abstain from coffee but more likely to drink regular coffee. Yet, reasons for the medical exam (feeling ill or health check-up) were not related to types of coffee.
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TABLE 4. Medical history and current problem queries related* to decaffeinated coffee use compared to no coffee usea Query
N (yes)
Odds ratio
Medical history: “Has a doctor ever said you had . . . ?” Hypertension 2055 1.3 Arthritis 1789 0.8 Current symptoms: “Do you now have . . . ?” Heart trouble 335 2.6 High blood pressure 1742 1.5 Take medication for heart 1932 1.4 Heart irregularity 925 1.4 Tired or rundown 2510 0.8 Unexplained weight loss 162 0.5 Trouble swallowing 233 0.5
95% CI
P-value
1.1–1.5 0.6–0.9
0.001 0.02
1.1–2.2 1.2–1.8 1.2–1.7 1.1–1.8 0.7–0.9 0.3–0.9 0.3–0.8
0.009 0.001 0.001 0.007 0.008 0.04 0.008
*Estimated by logistic regression adjusted for age, sex, race, education, cigarette smoking, and alcohol consumption. Table includes all items with p 0.05. (See appendix A for list of items not related). a Drinks only decaffeinated coffee (n 1,545) vs no coffee (n 2,837).
There were strong positive decaffeinated/caffeinated coffee associations (Table 5) for all special diets for which inquiry was made (low fat, low salt, low calorie, and vegetarian). Use of vitamin supplements, herbal/decaffeinated tea use, avoidance of caffeinated soda and medicine, and regular intense recreational exercise were also positively related to decaffeinated coffee use. Analyses limited to subsets of only disease-free individuals and of only persons with heart problems further explored the relationships (Table 5). For persons without past medical problems, the decaffeinated/caffeinated coffee use association with vegetarian diet was strengthened, while that for low cholesterol or low fat diet and avoidance of caf-
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feine in soft drink and medicine was weakened. In individuals with heart problems, slight weakening of the association with vegetarian diet and taking multiple vitamins were seen. For decaffeinated/abstainer comparisons, only lowsalt diet, low-calorie diet, and herbal/decaffeinated tea use showed significant associations (data not shown).
DISCUSSION These data show that use of decaffeinated coffee drinkers as a control group in epidemiological studies carries major problems. One evident difficulty is that most persons who drink decaffeinated coffee are former drinkers of regular coffee (15, 16). This is a fact of more importance in the study of possible long-term caffeine outcomes than in study of immediate or short-term effects. Control for demographic traits, smoking and alcohol use is clearly necessary, but usually done in epidemiological studies. Traits related to more decaffeinated coffee use in this analysis (older age and female sex) were also seen in two prior reports (15, 16), and this report adds AfricanAmerican ethnicity as a significant determinant. Perhaps the “knottiest” problem in studying health status or outcomes among decaffeinated coffee drinkers is the fact that many persons switch from caffeinated to decaffeinated coffee due to illnesses or symptoms. Prior reports (15, 16) indicate that decaffeinated coffee drinkers had poorer perceptions of their health status than regular coffee drinkers. Our data suggest that persons with history or symptoms of cardiovascular or gastrointestinal diseases tend to choose decaffeinated coffee instead of either regular coffee or none. We cannot establish temporality from the cross-section
TABLE 5. Dietary and other lifestyle related items associated with decaffeinated coffee use compared to caffeinated coffee, stratified by health status Lifestyle habits With heart problema
All Items Herbal/decaf tea Low salt diet Low cholesterol/fat diet Vegetarian diet Low calorie diet Take multiple vitamin pills No caffeinated soft drinks No caffeinated medicine High intensity activity Add salt most or all the time Regular tea
No medical historyb
OR*
95% CI
OR*
95% CI
OR*
95% CI
2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.2 1.2 0.6 0.5
1.7–2.4 1.6–2.2 1.5–2.1 1.2–2.4 1.3–1.9 1.2–1.7 1.2–1.6 1.1–1.4 1.1–1.4 0.5–0.7 0.5–0.6
1.5 1.7 2.0 1.8 1.6 1.2 1.2 1.4 1.3 0.4 0.5
1.1–2.1 1.4–2.2 1.6–2.6 1.0–3.4 1.2–2.2 0.9–1.6 1.0–1.5 1.1–1.8 1.1–1.6 0.3–0.6 0.4–0.6
1.7 1.9 1.5 3.4 1.8 1.6 1.4 1.3 1.3 0.6 0.6
1.1–2.6 1.2–3.2 0.9–2.6 1.6–7.3 1.1–2.9 1.1–2.5 1.0–1.9 0.9–1.8 1.0–1.8 0.4–0.9 0.4–0.9
*Adjusted for age, sex, race, education, cigarette smoking, high coffee consumption, and alcohol consumption. Only individuals who said one or more “yes” to the following query: now have heart trouble, arrhythmia, or hypertension; ever had heart disease, stroke, arrhythmia, or hypertension; currently taking medications for heart disease (n 3,244). b Only individuals who did not indicate a single positive response to any of the 30 medical history queries ( n 2,637). a
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data; i.e., whether individuals switched before or after they became ill. It seems likely that most decaffeinated coffee users with these problems were former caffeinated coffee drinkers. A survey of about 700 physicians found that over 75% recommended reduction in caffeine intake in patients with arrhythmia, tachycardia, or palpitations (17). Although persons who were free of all illnesses were unlikely to drink decaffeinated coffee, the individual motives among these persons may differ. Soroko et al (16) found that the most common reason given for switching from regular to decaffeinated coffee was personal belief that caffeine was bad for health. Our data show that a large proportion of decaffeinated coffee drinkers avoid other vehicles containing caffeine (tea, soft drinks, and medications. Indirect support of the hypothesis that some persons avoid caffeine as a part of a healthy lifestyle is found in the strong relations of decaffeinated coffee consumption to special diets, taking vitamin pills, and vigorous exercise. Perhaps the single most suggestive item in this regard was that, even among diseasefree individuals, vegetarians were more than 3 times as likely to choose decaffeinated coffee over caffeinated coffee. Some persons following special diets probably did so due to heart-related concerns, but the similar odds ratios for decaffeinated/caffeinated coffee illness-free persons and those with heart problems suggest disparate explanation. Caffeine content may not be the sole difference between regular and decaffeinated coffee. Until the mid-1970s, the organic solvent methods available for extraction of caffeine used potentially harmful compounds such as methylene chloride, benzene, chloroform, ether, trichloroethylene, carbon tetrachloride, acetone, ammonium hydroxide, and sulfuric acid (18). Methylene chloride, used extensively, was found to be a rodent carcinogen at high levels, and the Food and Drug Administration now regulates the residual amount of this compound in decaffeinated coffee (18, 19). Although newer, more inert water- or carbon dioxide-extraction methods have gained some popularity, methylene chloride and ethyl acetate are still commonly employed solvents. Compounds additional to caffeine might be extracted, or small amounts of solvent residue may remain in decaffeinated coffee beans. The relation of cardiovascular history to decaffeinated coffee use leads us to briefly review the unresolved issue of an association between coronary heart disease and total coffee consumption. If so, it is unlikely that caffeine is solely responsible. A lowdensity-lipoprotein-cholesterol raising compound, cafestol, is a lipid-soluble compound found in boiled or French-pressed coffee but removed by filtering through paper (type 34 to 41). Most decaffeinated coffees are made with robusta beans rather than arabica beans (11). Robusta contains a higher amount of the phenolic compounds (20) associated with plasma lipid elevation. We did find slightly higher total blood cholesterol levels in heavier coffee drinkers, but no independent relation to caf-
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feinated or decaffeinated coffee use (data not shown). In heavier non-filtered coffee drinkers of either type, this might contribute to higher coronary disease risk (21–24). Those receiving psychiatric care, having difficulty sleeping, and reporting loss of sexual interest in the past year, all possible indicators of depression or other emotional disturbance, were more likely to drink decaffeinated than regular coffee (Table 3). These results are compatible with observed associations of coffee intake to mood elevation or lower suicide risk (7, 25–27). It is unclear whether mental health professionals advise avoidance of caffeine, depressed persons avoid caffeine due to its anxiety-promoting effect, or caffeine is an anti-depressant. Clinical trials are needed in this area. This analysis has several limitations. First, as mentioned earlier, because the cross-sectional data were measured at a single point in time, we could not determine when or if decaffeinated drinkers switched from caffeinated coffee. Second, since the proportions of caffeinated/decaffeinated coffee were not requested in the large group categorized as users of both (caffeinated and decaffeinated coffee); this discouraged us from including this group into our analysis. In general, however, this group had demographics, habits, and measurements intermediate between those of the drinkers of caffeinated and decaffeinated coffee (data not shown). Third, there was no inquiry for amount of coffee per cup, preparation method, and reasons for choice of coffee type. Fourth, the data were collected in the mid-1980s; consumption patterns and the reasons for them may have changed over the intervening years. Consumption of coffee at home has been decreasing over the years while more people drink “gourmet” coffee, simultaneous with proliferation of coffeehouses in the United States over the last decade (10). Finally these data from Northern California may not be fully applicable to other areas, especially to other countries where use of decaffeinated coffee may vary. Even with these limitations, this large-scale study substantially supplements previous data about traits of individuals who choose to consume decaffeinated coffee. The areas of potential confounding that were suggested indicate the possibility of conflicting effects on risks. Similar conflicting effects might confound study of other lifestyle habit changes, such as smoking, alcohol drinking or diet. With respect to decaffeinated coffee, increased illness and symptoms in decaffeinated coffee drinkers might indicate likelihood of bias towards overestimating adverse outcomes. On the other hand, the healthier lifestyle of some drinkers of decaffeinated coffee might bias outcomes in their favor. All considered, we caution those who choose to use drinkers of decaffeinated coffee as a comparison group that caveat emptor. Funding/Support: This work was supported by grants from the Alcoholic Beverage Medical Research Foundation of Baltimore MD, and from The
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Scientific Advisory Group of the National Coffee Association of the USA. We thank Cynthia Landy for data collection, Harald Kipp for programming assistance and Sally McBride Allen for technical assistance.
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6. Hinds TS, West WL, Knight EM, Harland BF. The effect of caffeine on pregnancy outcome variables. Nutrition Reviews 1996;54:203–7. 7. Klatsky AL, Armstrong MA, Friedman GD. Coffee, tea, and mortality. Ann Epidemiol. 1993;3:375–381. 8. Klatsky AL, Armstrong MA. Alcohol, smoking, coffee, and cirrhosis. Am J Epidemiol. 1992;136:1248–1257.
APPENDIX A: Items tested but did not show significant associations with decaffeinated coffee use Current symptoms Dizzy spells or blackouts Chronic hoarseness Trouble with ears High cholesterol 240 Chronic cough Trouble breathing Chest pain/pressure Swelling of feet/legs Stomach pain Blood in stools Constipation Diarrhea Liver trouble Nervous, depressed, emotional tro Kidney trouble Pain in legs Pain in joints Thyroid trouble Swollen glands Overweight Anemia Diabetes Allergies Skin rash Reason for exam was due to illness Blood in urine Serious problems with drugs Serious problems with family Serious problems with finance Serious problems with marriage Serious problems with job
Past medical history Heart murmur Stroke Migraine Asthma Gout Seriously ill before Emotional problems Gallstone/gallbladder problem Liver disease Tuberculosis Colon/bowel disease Kidney/bladder stones Venereal disease Anemia Cancer Diabetes Epilepsy Thyroid disease Hay fever Glaucoma Psoriasis Kidney/bladder infection Emphysema
9. Heyden S, Tyroler HA, Heiss G, Hames CG, Bartel A. Coffee consumption and mortality. Total mortality, stroke mortality, and coronary heart disease mortality. Arch Intern Med. 1978;138:1472–1475. 10. NCA TNCAoU. National Coffee Drinking Trends. New York: National Coffee Association of USA; 2000. 11. Spiller G. The chemical components of coffee. In: Spiller M, ed. The methylxanthine beverages and foods: chemistry, consumption, and health effects. New York: Alan R Liss; 1984:91–148. 12. Collen MF, Davis LF. The multitest laboratory in health care. Occup Health Nurs. 1969;17:13–18. 13. Krieger N. Overcoming the absence of socioeconomic data in medical records: validation and application of a census-based methodology. Am J Public Health. 1992;82:703–710. 14. Klatsky AL, Petitti DB, Armstrong MA, Friedman GD. Coffee, tea and cholesterol. Am J Cardiol. 1985;55:577–578. 15. Leviton A, Allred EN. Correlates of decaffeinated coffee choice. Epidemiology. 1994;5:537–540. 16. Soroko S, Chang J, Barrett-Connor E. Reasons for changing caffeinated coffee consumption: the Rancho Bernardo Study. J Am Coll Nutr. 1996;15:97–101. 17. Hughes JR, Amori G, Hatsukami DK. A survey of physician advice about caffeine. J Subst Abuse. 1988;1:67–70. 18. Ramalakshmi K, Raghavan B. Caffeine in coffee: its removal. Why and how? Crit Rev Food Sci Nutr. 1999;39:441–456. 19. FDA FaDA. Cosmetics. proposed ban on the use of methylene chloride as an ingredient of aerosol cosmetic products. Fed. Reg. 1985; 50:51551–51559. 20. Eichler O. Kaffee und coffein. Berlin: Springer-Verlag; 1975. 21. Fried RE, Levine DM, Kwiterovich PO, Diamond EL, Wilder LB, Moy TF, et al. The effect of filtered-coffee consumption on plasma lipid levels. Results of a randomized clinical trial. [see comments] JAMA. 1992;267:811–815. 22. Wei M, Macera CA, Hornung CA, Blair SN. The impact of changes in coffee consumption on serum cholesterol. J Clin Epidemiol. 1995;48:1189–1196. 23. Urgert R, Katan MB. The cholesterol-raising factor from coffee beans. Annu Rev Nutr. 1997;17:305–324.
REFERENCES 1. Weinberg BA, Bealer BK. The world of caffeine: the science and culture of the world’s most popular drug. New York: Routledge; 2001. 2. Garattini S. Caffeine, coffee, and health. New York: Raven Press, 1993. 3. Curatolo PW, Robertson D. The health consequences of caffeine. Ann Intern Med. 1983;98:641–653. 4. Kawachi I, Colditz GA, Stone CB. Does coffee drinking increase the risk of coronary heart disease? Results from a meta-analysis. British Heart Journal 1994;72:269–75. 5. La Vecchia C. Coffee and cancer epidemiology. In: Garattini S, ed. Caffeine, coffee, and health. Milan: Raven Press, 1993.
24. Superko HR, Bortz W Jr, Williams PT, Albers JJ, Wood PD. Caffeinated and decaffeinated coffee effects on plasma lipoprotein cholesterol, apolipoproteins, and lipase activity: a controlled, randomized trial. [see comments]Am J Clin Nutr. 1991;54:599–605. 25. Quinlan P, Lane J, Aspinall L. Effects of hot tea, coffee and water ingestion on physiological responses and mood: the role of caffeine, water and beverage type. Psychopharmacology (Berl). 1997;134:164– 173. 26. Quinlan PT, Lane J, Moore KL, Aspen J, Rycroft JA, O’Brien DC. The acute physiological and mood effects of tea and coffee: the role of caffeine level. Pharmacol Biochem Behav. 2000;66:19–28. 27. Hindmarch I, Quinlan PT, Moore KL, Parkin C. The effects of black tea and other beverages on aspects of cognition and psychomotor performance. Psychopharmacology (Berl). 1998;139:230–238.
PURPOSE: Little is known about the traits of decaffeinated coffee drinkers, who are sometimes used to ascertain whether the health effects of coffee intake are due to caffeine or some other coffee ingredient. METHODS: We studied these traits in 12,467 persons who reported type of coffee consumed at health examinations; 36% drank caffeinated only, 13% drank decaffeinated only, 27% drank both types and 24% drank no coffee. RESULTS: Odds ratios estimated from logistic regression analyses revealed that compared with regular (caffeinated) coffee drinkers or abstainers, decaffeinated coffee drinkers were less likely to be heavy coffee drinkers, smokers, alcohol drinkers, users of caffeinated soft drinks and medication and to be free of illness. Increased decaffeinated coffee drinking was associated with older age, female sex, African American ethnicity, use of special diets and cardiovascular, gastrointestinal, or neuropsychiatric symptoms. Persons on special diets were more likely to drink decaffeinated coffee whether they had heart disease or were free of any illness. CONCLUSION: These data suggest that decaffeinated coffee use is related to illness in some persons but to a healthy lifestyle in others. These potential and possibly conflicting confounding factors need to be considered when studying the health effects of coffee or caffeine. Ann Epidemiol 2003;13:273–279. © 2003 Elsevier Science Inc. All rights reserved. KEY WORDS:
Caffeine, Coffee, Decaffeinated Coffee, Risk Factors, Epidemiology.
INTRODUCTION Although caffeine is believed to be the most widely consumed and studied drug in history (1), most questions regarding its health effects remain unanswered (2, 3). Research results are inconclusive about both adverse and beneficial relations of caffeine to several health outcomes. Possible adverse relations include those to coronary heart disease (4), fibrocystic breast disease (2, 3), several types of cancer, (5), and reproductive health effects (6). Possible beneficial relations include reduced risk of suicide (7) or liver cirrhosis (8). No overall effect on mortality has been found (7, 9). Yet, due to the high prevalence of its use, even small health effects of caffeine might cause a substantial public health impact. Approximately 80% of Americans consume coffee, and among coffee drinkers the average US consumption is 3.1 cups of coffee per day (10). Coffee drinking is sometimes considered a marker for caffeine intake, and caffeine’s stimulatory property makes it the most obvious and most studied compound in coffee.
From the School of Public Health, University of California, Berkeley, CA (A.K.S.); and the Division of Research, Kaiser Permanente Medical Care Program, Oakland, CA (A.L.K., M.A.A.) Address correspondences to: Arthur L. Klatsky, MD, Kaiser Permanente Medical Center, 280 West MacArthur Boulevard, Oakland, CA 94611, USA. Tel.: (510) 450-2757; Fax: (510) 572-7456. E-mail: alk@dor. kaiser.org Received October 31, 2001; revised March 25, 2002; accepted May 3, 2002. © 2003 Elsevier Science Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010
Although coffee contains hundreds of other potentially biologically active compounds (11), caffeine is often automatically singled out as the culprit of negative health outcomes. The studies of coffee and health must also take into account that coffee use is associated with smoking, alcohol consumption, less physical exercise, and unhealthy dietary habits (4–5, 8–9). Relationships between decaffeinated coffee use and health are sometimes used as an indicator of whether apparent coffee effects are likely due to caffeine or some other coffee ingredients. Little is known, however, about differential relations of potential confounders to regular or decaffeinated coffee use. It is possible that any apparent disparities in disease outcomes between caffeinated and decaffeinated drinkers are due to differences in life-styles or medical history between the two groups, rather than to the effect of caffeine. To supplement the limited available data, we explored the associations between type of coffee consumed to demographics, medical history, current health status, and lifestyle habits for a multi-ethnic sample of 12,467 persons.
SUBJECTS AND METHODS Study Population and Data The study protocols were approved by the Institutional Review Board of the Kaiser Permanente Medical Care Program. Subjects were 12,467 persons who supplied data 1047-2797/03/$–see front matter PII S1047-2797(02)00414-3
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Selected Abbreviations and Acronyms CI confidence interval MHC multiphasic health checkup OR odds ratio
about the type of coffee they drank at health examinations in 1984–1985. The examination, known as a Multiphasic Health Checkup (MHC), was offered for decades at the Oakland and San Francisco facilities of a large Northern California prepaid health care organization (12). Examinees voluntarily provided information during this routine health examination. Subjects represented a reasonable cross-section of the population in the area served (13), although “health conscious” persons were probably somewhat over-represented and the medically indigent were underrepresented. Subjects supplied demographic data, medical history information, and data about alcohol use, smoking, and total number of cups of coffee drunk per day on other questionnaires at the MHC. The questionnaires included queries about (i) reason for taking the examination; (ii) current symptoms, problems, and treatments; (iii) past diagnoses, surgical operations, and risk factors; and (iv) psycho-social problems. Health measurements and laboratory tests were done, which included height, weight, systolic and diastolic blood pressure, hemoglobin, leukocyte count, creatinine, glucose, and total cholesterol levels. A supplementary questionnaire was offered at the end of the examination, and coffee type query was answered by 71% (12,467/17,680) of all examinees. Most of this disparity was due to absences of the special research clerk during which no supplementary forms were distributed. A smaller proportion declined the supplement, the precise number is not known. Distributions of demographic and outcome variables in these subjects were very similar to those of all 17,680 MHC examinees in the years involved. The coffee type query was “If you drink coffee, what type do you drink?”, with these options: “regular (caffeinated) coffee only”, “decaffeinated coffee only”, “both regular and decaffeinated coffee”, and “never or almost never drink coffee.” Subjects (n 369) who checked “never or almost never” on the coffee type query but stated an amount of coffee elsewhere were excluded from analyses; (83% of these stated 1 cup per day). Analytic Methods Simple cross-classifications were done to examine demographic differences. Statistical analyses were performed using SAS for Windows (version 8.1) statistical software package (SAS Institute Inc., Cary, NC). For analyses presented here, exclusive use of decaffeinated coffee was the study end point.
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Multivariate logistic regressions, yielding odds ratios from coefficients, were performed to estimate the relations between decaffeinated coffee use and items of interest. The items included: (i) health measurements; (ii) each of the 30 queries regarding medical history (“has a doctor ever said you have . . . ?”); (iii) each of the 46 current symptoms queries (“do you now have . . . ?”); (iv) queries about special diets (low salt, low fat, low calorie, vegetarian); (v) and recreational physical activity. Composite variables were constructed for (i) possible cardiovascular disease-related items (one or more “yes” to: now have heart trouble, heart irregularity, palpitations, or high blood pressure; ever had heart disease, stroke, arrhythmia, or hypertension; currently taking medications for heart disease: n 3244); (ii) possible gastrointestinal disease-related items (now have trouble swallowing, diarrhea, constipation, stomach pain, or liver trouble; ever had liver or colon/bowel disease: n 3345); and (iii) high intensity recreational physical activities ( once/week swimming, jogging/running, outdoor bicycling, stationary bicycling, calisthenics, exercise class, gym workouts, or tennis: n 5220). For each query, two separate regressions were done to estimate the likelihood of decaffeinated coffee use compared with (i) users of regular coffee only or (ii) nondrinkers of coffee. The reference groups were persons who answered “no” to the respective queries. Thus, no comparisons were made for persons who drank both caffeinated and decaffeinated coffee. All models were adjusted for; age (continuous), race (white as referent, black, others), sex (female as referent), smoking status (never as referent, ex-smoker, 1pack/ day, 1/day), usual alcohol intake (never as referent, exdrinker, 1drink/day, 1 to 2 drinks/day, 3 drinks/day drinkers), and educational attainment (no college as referent, partial college, college graduate), marital status (currently married as referent, formerly married, never married). Amount of coffee intake (4 or 4 cups/day) was also included in the model that compared decaffeinated to caffeinated coffee use.
RESULTS Coffee Type by Demographic Traits and Habits Of the 12,098 persons who supplied valid coffee type data 36% (n 4409) of the subjects that drank caffeinated coffee only, 13% (n 1545) decaffeinated coffee only, 27% (n 3,307) both caffeinated and decaffeinated coffee, and 24% (n 2,837) no coffee (Table 1). Persons drinking four or more cups of coffee a day were less likely to drink decaffeinated coffee only. Prevalence of exclusive decaffeinated coffee use tripled from ages younger than 40 years to age 60 and older and, compared with other categories, was relatively greater among women, blacks, those without college education, non-alcohol drinkers, and
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TABLE 1. Characteristics of study subjects classified by coffee types Traits Number of persons*
Gender Male Female Ethnicity Blacks Whites Others Age 40 40-59 60 Education No college Some college College Marital status Currently married Never married Formerly married Cigarette smoking Never Ex-smoker 1 pack/day 1 pack/day Alcohol Never Ex-drinker 1 drink/day 1-2 drinks/day 3 drinks/day Coffee (cups/day) Never/occasional 4 cups/day 4cups/day Tea (cups/day) Never/occasional 4 cups/day 4cups/day
Total 12098
Regular only 4409
Decaf only 1545
Both 3307
None 2837
N
%*
%*
%*
%*
5230 6868
40.5 33.3
10.4 14.6
26.6 27.9
22.5 24.2
3170 6857 2007
28.3 40.2 36.3
14.4 12.1 12.6
22.2 29.4 28.6
35.1 18.4 22.5
4951 4362 2785
38.0 35.1 35.7
6.8 14.5 20.7
23.2 32.1 27.3
32.0 18.3 16.3
4513 3133 4452
36.5 36.3 36.5
15.4 11.0 11.3
25.4 25.1 30.9
22.7 27.6 21.3
6530 2150 2301
36.3 37.4 34.9
14.1 5.7 15.9
28.7 21.9 29.3
21.0 35.0 19.9
7209 2822 1351 716
32.6 38.6 43.7 52.9
12.5 14.7 12.1 9.4
26.4 30.5 26.3 26.0
28.5 16.2 18.0 11.7
1802 537 6695 2223 841
22.9 31.8 35.7 45.8 49.5
15.4 14.2 12.9 11.5 8.8
20.5 26.1 28.5 30.0 26.6
41.2 27.9 22.9 12.7 15.1
3269 7013 1722
3.2 47.4 56.0
7.3 16.2 8.8
3.9 36.4 35.3
85.6 N/A N/A
6506 5224 246
39.2 33.3 28.1
12.2 13.3 12.2
24.2 31.5 24.8
24.4 21.9 35.0
*The percentage of each row may not sum up to 100% due to rounding and the total N may not add up for some categories due to missing values.
ex-smokers. Decaffeinated use only was less prevalent among never married persons, heavy smokers, and daily alcohol drinkers. More than half of all persons drinking four or more cups of coffee per day drank only regular (caffeinated) coffee. Prevalence of regular coffee drinking was higher in males, whites, current smokers, and daily alcohol drinkers, and little related to age, educational attainment, or marital status. Coffee abstinence was more prevalent among persons who were black, younger than 40 years, and never married, smoked, or consumed alcohol. The characteristics of persons reporting use of both caffeinated and decaffeinated coffee fell between those of the regular and decaffeinated coffee only groups.
Multivariate analyses (Table 2) showed that many relations were independently significant, including inverse associations of decaffeinated coffee use (vs. caffeinated) with current alcohol use, 1 pack or more/day of cigarette smoking, 4 cups or more/day of coffee drinking, and never married status. Age, female sex, and black race showed positive relations. When decaffeinated coffee drinkers were compared with abstainers, independent inverse associations were present for black race, never married status, and partial college education status, while positive associations were found for female sex, current alcohol use and current or past cigarette use (see Table 2). No association was found between any health measurement (hemoglobin, leukocyte count, creatinine, glucose,
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TABLE 2. Adjusted association of traits and demographics with decaffeinated coffee use vs. Regular coffee users Traits Sex Male Female Ethnicity White Black Others Alcohol use Never Ex–drinkers 1drink/day 1–2 drinks/day 3 drinks/day Cigarette smoking Never Ex–smoker Current 1pack/day Current 1pack/day Educational attainment No college Partial college College graduate Marital status Currently married Formerly married Never married Coffee consumption 4 cups/day 4 cups/day
OR*
95% CI
TABLE 3. Medical history and current problem queries related* to decaffeinated coffee use compared to regular (caffeinated) coffee usea
vs. Abstainers OR*
95% CI
1.0 1.6
Ref. 1.4–1.8
1.0 1.9
Ref. 1.6–2.2
1.0 1.6 1.1
Ref. 1.3–1.8 1.0–1.4
1.0 0.8 1.6
Ref. 0.7–1.0 1.3–2.0
1.0 1.0 0.8 0.6 0.5
Ref. 0.7–1.4 0.6–0.9 0.5–0.7 0.3–0.7
1.0 1.3 2.1 2.8 2.0
Ref. 0.9–1.8 1.7–2.5 2.2–3.6 1.4–2.9
1.0 1.1 0.9 0.8
Ref. 0.9–1.3 0.7–1.1 0.6–1.0
1.0 1.6 2.0 2.0
Ref. 1.3–1.9 1.6–2.6 1.4–2.9
1.0 0.9 1.1
Ref. 0.8–1.1 1.0–1.3
1.0 0.7 0.9
Ref. 0.6–0.9 0.8–1.1
1.0 1.0 0.6
Ref. 0.9–1.2 0.5–0.8
1.0 1.0 0.5
Ref. 0.8–1.2 0.4–0.7
1.0 0.4
Ref. 0.3–0.5
N/A N/A
*Odds Ratio estimated by logistic regression adjusted for age, sex, race, education, cigarette smoking, and alcohol consumption.
and total cholesterol) and decaffeinated coffee use (data not shown). However, high cholesterol level (240 mg/dl) was related to total coffee consumption (4 cups/day) (OR 1.2; 95% CI 1.1–1.3), confirming our findings (14) of a total coffee-cholesterol relation in an earlier incomplete dataset in this study population. Medical History, Symptoms, and Decaffeinated Coffee Use A third (6/18) of items showing significant relations to decaffeinated coffee use were related to heart disease (Table 3). Assuming strong inter-item correlation, a cardiovascular disease composite (described earlier) was tested, yielding a decaffeinated/caffeinated odds ratio of 1.5 (95% CI 1.3– 1.7, P 0.001). Similar analyses of decaffeinated coffee users versus abstainers showed that over half (5/9) of the items significantly associated with decaffeinated coffee use was cardiovascular related (Table 4). In this comparison, the odds ratio for the cardiovascular composite was 1.3
Query
N (yes)
Odds ratio
95% CI
Medical history: “Has a doctor ever said you had . . . ?” Heart disease 326 2.4 1.7–3.3 Hiatal hernia 524 1.7 1.3–2.2 Stomach/duodenal ulcer 676 1.6 1.3–2.1 Hypertension 2125 1.4 1.2–1.6 Hospitalization 716 1.3 1.0–1.6 No “yes” responses 2555 0.8 0.7–0.9 Current problems: “Do you now have . . . ?” Heart trouble 326 2.2 1.6–3.0 Psychiatric care 447 1.5 1.2–2.1 Medication for heart 1998 1.5 1.3–1.7 High blood pressure 1683 1.4 1.2–1.6 Difficulty sleeping 1855 1.4 1.2–1.6 Loss of sexual interest 879 1.3 1.1–1.7 Heart irregularity 906 1.3 1.1–1.6 Stomach pain 1033 1.3 1.1–1.6 Back trouble 2305 1.3 1.1–1.5 Severe headache 1590 1.2 1.0–1.5 Trouble with eyes 2105 1.2 1.0–1.4 No “yes” responses 1526 0.8 0.6–0.9
P-value 0.001 0.001 0.001 0.001 0.04 0.02 0.001 0.02 0.001 0.001 0.001 0.01 0.008 0.01 0.003 0.02 0.02 0.006
*Estimated by logistic regression adjusted for age, sex, race, education, cigarette smoking, and alcohol consumption. Table includes all items with p 0.05. (See appendix A for list of items not significantly related). a Drinks only decaffeinated coffee (n 1,545) vs only caffeinated coffee (n 4,409).
(95% CI 1.2–1.6). Therefore, persons with cardiovascular problems are more likely to choose decaffeinated coffee instead of either regular coffee or none. Three gastrointestinal system-related items showed significant relationships for decaffeinated/caffeinated coffee use (see Table 3). These were all related to the upper gastrointestinal area (hiatal hernia, stomach/duodenal ulcer, stomach pain). The odds ratio for the gastrointestinal composite was 1.3 (95% CI 1.1–1.5). No similar gastrointestinal associations were seen for the decaffeinated versus abstainer comparisons. Individuals who did not indicate a single positive response to any of the 30 medical history queries (n 2555) or to any of the 46 current symptoms (n 1526), thus presumably healthy individuals, were significantly less likely to be decaffeinated coffee drinkers. However, these individuals were neither more nor less likely to drink decaffeinated coffee than to be coffee abstainers. A separate analyses showed that those without any current symptoms are slightly more likely to choose regular coffee than none (OR 1.2, P 0.02). These presumably healthy individuals were, thus, less likely to consume decaffeinated coffee or to abstain from coffee but more likely to drink regular coffee. Yet, reasons for the medical exam (feeling ill or health check-up) were not related to types of coffee.
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TABLE 4. Medical history and current problem queries related* to decaffeinated coffee use compared to no coffee usea Query
N (yes)
Odds ratio
Medical history: “Has a doctor ever said you had . . . ?” Hypertension 2055 1.3 Arthritis 1789 0.8 Current symptoms: “Do you now have . . . ?” Heart trouble 335 2.6 High blood pressure 1742 1.5 Take medication for heart 1932 1.4 Heart irregularity 925 1.4 Tired or rundown 2510 0.8 Unexplained weight loss 162 0.5 Trouble swallowing 233 0.5
95% CI
P-value
1.1–1.5 0.6–0.9
0.001 0.02
1.1–2.2 1.2–1.8 1.2–1.7 1.1–1.8 0.7–0.9 0.3–0.9 0.3–0.8
0.009 0.001 0.001 0.007 0.008 0.04 0.008
*Estimated by logistic regression adjusted for age, sex, race, education, cigarette smoking, and alcohol consumption. Table includes all items with p 0.05. (See appendix A for list of items not related). a Drinks only decaffeinated coffee (n 1,545) vs no coffee (n 2,837).
There were strong positive decaffeinated/caffeinated coffee associations (Table 5) for all special diets for which inquiry was made (low fat, low salt, low calorie, and vegetarian). Use of vitamin supplements, herbal/decaffeinated tea use, avoidance of caffeinated soda and medicine, and regular intense recreational exercise were also positively related to decaffeinated coffee use. Analyses limited to subsets of only disease-free individuals and of only persons with heart problems further explored the relationships (Table 5). For persons without past medical problems, the decaffeinated/caffeinated coffee use association with vegetarian diet was strengthened, while that for low cholesterol or low fat diet and avoidance of caf-
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feine in soft drink and medicine was weakened. In individuals with heart problems, slight weakening of the association with vegetarian diet and taking multiple vitamins were seen. For decaffeinated/abstainer comparisons, only lowsalt diet, low-calorie diet, and herbal/decaffeinated tea use showed significant associations (data not shown).
DISCUSSION These data show that use of decaffeinated coffee drinkers as a control group in epidemiological studies carries major problems. One evident difficulty is that most persons who drink decaffeinated coffee are former drinkers of regular coffee (15, 16). This is a fact of more importance in the study of possible long-term caffeine outcomes than in study of immediate or short-term effects. Control for demographic traits, smoking and alcohol use is clearly necessary, but usually done in epidemiological studies. Traits related to more decaffeinated coffee use in this analysis (older age and female sex) were also seen in two prior reports (15, 16), and this report adds AfricanAmerican ethnicity as a significant determinant. Perhaps the “knottiest” problem in studying health status or outcomes among decaffeinated coffee drinkers is the fact that many persons switch from caffeinated to decaffeinated coffee due to illnesses or symptoms. Prior reports (15, 16) indicate that decaffeinated coffee drinkers had poorer perceptions of their health status than regular coffee drinkers. Our data suggest that persons with history or symptoms of cardiovascular or gastrointestinal diseases tend to choose decaffeinated coffee instead of either regular coffee or none. We cannot establish temporality from the cross-section
TABLE 5. Dietary and other lifestyle related items associated with decaffeinated coffee use compared to caffeinated coffee, stratified by health status Lifestyle habits With heart problema
All Items Herbal/decaf tea Low salt diet Low cholesterol/fat diet Vegetarian diet Low calorie diet Take multiple vitamin pills No caffeinated soft drinks No caffeinated medicine High intensity activity Add salt most or all the time Regular tea
No medical historyb
OR*
95% CI
OR*
95% CI
OR*
95% CI
2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.2 1.2 0.6 0.5
1.7–2.4 1.6–2.2 1.5–2.1 1.2–2.4 1.3–1.9 1.2–1.7 1.2–1.6 1.1–1.4 1.1–1.4 0.5–0.7 0.5–0.6
1.5 1.7 2.0 1.8 1.6 1.2 1.2 1.4 1.3 0.4 0.5
1.1–2.1 1.4–2.2 1.6–2.6 1.0–3.4 1.2–2.2 0.9–1.6 1.0–1.5 1.1–1.8 1.1–1.6 0.3–0.6 0.4–0.6
1.7 1.9 1.5 3.4 1.8 1.6 1.4 1.3 1.3 0.6 0.6
1.1–2.6 1.2–3.2 0.9–2.6 1.6–7.3 1.1–2.9 1.1–2.5 1.0–1.9 0.9–1.8 1.0–1.8 0.4–0.9 0.4–0.9
*Adjusted for age, sex, race, education, cigarette smoking, high coffee consumption, and alcohol consumption. Only individuals who said one or more “yes” to the following query: now have heart trouble, arrhythmia, or hypertension; ever had heart disease, stroke, arrhythmia, or hypertension; currently taking medications for heart disease (n 3,244). b Only individuals who did not indicate a single positive response to any of the 30 medical history queries ( n 2,637). a
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data; i.e., whether individuals switched before or after they became ill. It seems likely that most decaffeinated coffee users with these problems were former caffeinated coffee drinkers. A survey of about 700 physicians found that over 75% recommended reduction in caffeine intake in patients with arrhythmia, tachycardia, or palpitations (17). Although persons who were free of all illnesses were unlikely to drink decaffeinated coffee, the individual motives among these persons may differ. Soroko et al (16) found that the most common reason given for switching from regular to decaffeinated coffee was personal belief that caffeine was bad for health. Our data show that a large proportion of decaffeinated coffee drinkers avoid other vehicles containing caffeine (tea, soft drinks, and medications. Indirect support of the hypothesis that some persons avoid caffeine as a part of a healthy lifestyle is found in the strong relations of decaffeinated coffee consumption to special diets, taking vitamin pills, and vigorous exercise. Perhaps the single most suggestive item in this regard was that, even among diseasefree individuals, vegetarians were more than 3 times as likely to choose decaffeinated coffee over caffeinated coffee. Some persons following special diets probably did so due to heart-related concerns, but the similar odds ratios for decaffeinated/caffeinated coffee illness-free persons and those with heart problems suggest disparate explanation. Caffeine content may not be the sole difference between regular and decaffeinated coffee. Until the mid-1970s, the organic solvent methods available for extraction of caffeine used potentially harmful compounds such as methylene chloride, benzene, chloroform, ether, trichloroethylene, carbon tetrachloride, acetone, ammonium hydroxide, and sulfuric acid (18). Methylene chloride, used extensively, was found to be a rodent carcinogen at high levels, and the Food and Drug Administration now regulates the residual amount of this compound in decaffeinated coffee (18, 19). Although newer, more inert water- or carbon dioxide-extraction methods have gained some popularity, methylene chloride and ethyl acetate are still commonly employed solvents. Compounds additional to caffeine might be extracted, or small amounts of solvent residue may remain in decaffeinated coffee beans. The relation of cardiovascular history to decaffeinated coffee use leads us to briefly review the unresolved issue of an association between coronary heart disease and total coffee consumption. If so, it is unlikely that caffeine is solely responsible. A lowdensity-lipoprotein-cholesterol raising compound, cafestol, is a lipid-soluble compound found in boiled or French-pressed coffee but removed by filtering through paper (type 34 to 41). Most decaffeinated coffees are made with robusta beans rather than arabica beans (11). Robusta contains a higher amount of the phenolic compounds (20) associated with plasma lipid elevation. We did find slightly higher total blood cholesterol levels in heavier coffee drinkers, but no independent relation to caf-
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feinated or decaffeinated coffee use (data not shown). In heavier non-filtered coffee drinkers of either type, this might contribute to higher coronary disease risk (21–24). Those receiving psychiatric care, having difficulty sleeping, and reporting loss of sexual interest in the past year, all possible indicators of depression or other emotional disturbance, were more likely to drink decaffeinated than regular coffee (Table 3). These results are compatible with observed associations of coffee intake to mood elevation or lower suicide risk (7, 25–27). It is unclear whether mental health professionals advise avoidance of caffeine, depressed persons avoid caffeine due to its anxiety-promoting effect, or caffeine is an anti-depressant. Clinical trials are needed in this area. This analysis has several limitations. First, as mentioned earlier, because the cross-sectional data were measured at a single point in time, we could not determine when or if decaffeinated drinkers switched from caffeinated coffee. Second, since the proportions of caffeinated/decaffeinated coffee were not requested in the large group categorized as users of both (caffeinated and decaffeinated coffee); this discouraged us from including this group into our analysis. In general, however, this group had demographics, habits, and measurements intermediate between those of the drinkers of caffeinated and decaffeinated coffee (data not shown). Third, there was no inquiry for amount of coffee per cup, preparation method, and reasons for choice of coffee type. Fourth, the data were collected in the mid-1980s; consumption patterns and the reasons for them may have changed over the intervening years. Consumption of coffee at home has been decreasing over the years while more people drink “gourmet” coffee, simultaneous with proliferation of coffeehouses in the United States over the last decade (10). Finally these data from Northern California may not be fully applicable to other areas, especially to other countries where use of decaffeinated coffee may vary. Even with these limitations, this large-scale study substantially supplements previous data about traits of individuals who choose to consume decaffeinated coffee. The areas of potential confounding that were suggested indicate the possibility of conflicting effects on risks. Similar conflicting effects might confound study of other lifestyle habit changes, such as smoking, alcohol drinking or diet. With respect to decaffeinated coffee, increased illness and symptoms in decaffeinated coffee drinkers might indicate likelihood of bias towards overestimating adverse outcomes. On the other hand, the healthier lifestyle of some drinkers of decaffeinated coffee might bias outcomes in their favor. All considered, we caution those who choose to use drinkers of decaffeinated coffee as a comparison group that caveat emptor. Funding/Support: This work was supported by grants from the Alcoholic Beverage Medical Research Foundation of Baltimore MD, and from The
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Shlonsky et al. TRAITS OF DECAFFEINATED COFFEE DRINKERS
Scientific Advisory Group of the National Coffee Association of the USA. We thank Cynthia Landy for data collection, Harald Kipp for programming assistance and Sally McBride Allen for technical assistance.
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6. Hinds TS, West WL, Knight EM, Harland BF. The effect of caffeine on pregnancy outcome variables. Nutrition Reviews 1996;54:203–7. 7. Klatsky AL, Armstrong MA, Friedman GD. Coffee, tea, and mortality. Ann Epidemiol. 1993;3:375–381. 8. Klatsky AL, Armstrong MA. Alcohol, smoking, coffee, and cirrhosis. Am J Epidemiol. 1992;136:1248–1257.
APPENDIX A: Items tested but did not show significant associations with decaffeinated coffee use Current symptoms Dizzy spells or blackouts Chronic hoarseness Trouble with ears High cholesterol 240 Chronic cough Trouble breathing Chest pain/pressure Swelling of feet/legs Stomach pain Blood in stools Constipation Diarrhea Liver trouble Nervous, depressed, emotional tro Kidney trouble Pain in legs Pain in joints Thyroid trouble Swollen glands Overweight Anemia Diabetes Allergies Skin rash Reason for exam was due to illness Blood in urine Serious problems with drugs Serious problems with family Serious problems with finance Serious problems with marriage Serious problems with job
Past medical history Heart murmur Stroke Migraine Asthma Gout Seriously ill before Emotional problems Gallstone/gallbladder problem Liver disease Tuberculosis Colon/bowel disease Kidney/bladder stones Venereal disease Anemia Cancer Diabetes Epilepsy Thyroid disease Hay fever Glaucoma Psoriasis Kidney/bladder infection Emphysema
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