Confounders contributing to the reported associations of coffee or caffeine with disease

Schreiber, George B.; Robins, Morton; Maffeo, Carla; Masters, Mary N.; Bond, Annell; Morganstein, David

doi:10.1016/0091-7435(88)90005-9

Cited by 75 publications

(37 citation statements)

References 26 publications

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“…8 The inconsistencies in the reported studies can partially be attributed to methodological defects and failure to control confounding variables, including baseline BP, smoking habits, sex differences, dietary and alcohol intake, stress, and obesity, as well as inaccurate determination of daily coffee and caffeine intake. 17,18 It is likely that different distribution of coffee habitus within these studies may, in accordance with our observations, account for some of the inconsistencies of the studies analyzing the hypertensive potential of coffee. In this context, studies showing acute increase in BP were conducted in nonhabitual drinkers or in habitual drinkers after a prolonged abstinence only.…”

Section: Discussionsupporting

confidence: 76%

Coffee Acutely Increases Sympathetic Nerve Activity and Blood Pressure Independently of Caffeine Content

et al. 2002

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Background-Coffee is the most abundantly consumed stimulant worldwide. However, its cardiovascular safety remains controversial. Possible health hazards have been related to its main ingredient, caffeine. Activation of the sympathetic nervous system by coffee may enhance cardiovascular risk; however, it is unclear whether this effect of coffee is related to caffeine or other substance(s) also contained in decaffeinated coffee. Methods and Results-In 15 healthy volunteers (6 habitual and 9 nonhabitual coffee drinkers) arterial blood pressure (BP), heart rate, and muscle sympathetic nervous activity (MSA) were continuously recorded before and after drinking a triple espresso or a decaffeinated triple espresso or after intravenous administration of caffeine (250 mg) or placebo (saline) in the same subjects. There was a significant time ϫ condition interaction for the intravenous caffeine and placebo conditions for MSA, with caffeine showing a significant increase in MSA at 60 minutes (53.2Ϯ14.1% total activity) and the placebo group showing no effect. A similar significant time effect was found for coffee drinking (54.1Ϯ22.5% total activity). Habitual and nonhabitual coffee drinkers demonstrated similar changes in MSA and BP after intravenous caffeine, whereas coffee drinking increased BP in nonhabitual drinkers only, despite comparable increases of MSA and plasma caffeine levels. Nonhabitual coffee drinkers showed similar activation of MSA and BP after caffeine infusion, coffee, or decaffeinated coffee. Conclusions-Acutely, coffee and caffeine induced comparable increases in MSA and BP in nonhabitual coffee drinkers, whereas habitual coffee drinkers exhibited lack of BP increase despite MSA activation to coffee. Because decaffeinated coffee also increases BP and MSA in nonhabitual drinkers, ingredients other than caffeine must be responsible for cardiovascular activation.

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Section: Discussionsupporting

confidence: 76%

Coffee Acutely Increases Sympathetic Nerve Activity and Blood Pressure Independently of Caffeine Content

et al. 2002

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“…39,40 Coffee consumption and cigarette smoking may be positively correlated. 41,42 We previously found no association between smoking and risk of breast cancer in this study population; 43 nevertheless, we did take into account the possible confounding effect of smoking in our analysis and found no modification of the coffee effect. Recently, CYP1A2 activity was positively related to caffeine intake among premenopausal women.…”

Section: Discussionmentioning

confidence: 57%

Coffee consumption and breast cancer risk among BRCA1 and BRCA2 mutation carriers

Nkondjock

Ghadirian

Kotsopoulos

et al. 2005

Intl Journal of Cancer

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Although there are several plausible biologic mechanisms whereby coffee consumption might influence the risk of breast cancer, epidemiologic evidence is limited. We assessed the association between coffee consumption and breast cancer risk among high-risk women who carry BRCA mutations. We performed a matched case-control analysis on 1,690 women with a BRCA1 or BRCA2 mutation from 40 centers in 4 countries. Average lifetime coffee consumption was estimated via a self-administered questionnaire. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression. After adjustment for potential confounders, the ORs for breast cancer in BRCA carriers who habitually drank 0, 1-3, 4-5 and 6 or more cups of coffee were 1.00, 0.90 (95% CI 0.72-1.12), 0.75 (95% CI 0.47-1.19) and 0.31 (95% CI 0.13-0.71; p-trend 5 0.02). The effect was limited to the consumption of caffeinated coffee. These results suggest that among women with BRCA gene mutation, coffee consumption is unlikely to be harmful and that high levels of consumption may in fact be related to reduced breast cancer risk. ' 2005 Wiley-Liss, Inc.Key words: BRCA1; BRCA2; breast cancer; coffee; case-control study Coffee is among the most widely consumed beverages in the world and is a major source of dietary caffeine. Over the last 2 decades, coffee and caffeine have been studied with regard to their potential role in breast cancer etiology. A number of animal studies have reported caffeine to both stimulate and to suppress breast tumors, depending upon the species and the phase of administration. 1 Coffee consumption (or caffeine intake) has been directly associated with plasma estradiol, estrone and sex hormone-binding globulin levels, and inversely associated with testosterone. 2,3 Coffee consumption also induces cell differentiation 4 and may inhibit mitosis. 5 These effects suggest that coffee consumption may affect breast cancer risk, but epidemiologic evidence supporting the association between coffee consumption and breast cancer risk is scant. A decrease in breast cancer risk in women with high levels of coffee consumption has been reported in several studies, 6,7 but other investigators have detected no relationship between coffee consumption and breast cancer risk. 1,8 It has been estimated that the risk of developing breast cancer among women with a mutation in BRCA1 or BRCA2 is as high as 80% by the age of 70. 9 Whether or not coffee affects BRCArelated breast cancer risk is currently unknown. To address this issue, we examined the association between coffee consumption and the risk of breast cancer among women with BRCA1 and BRCA2 gene mutations from 40 participating centers in 4 countries. Material and methods Study population and designThe study population has been described elsewhere. 10 Briefly, eligible study subjects included women who were currently alive and were known to be carriers of deleterious mutations of the BRCA1 or BRCA2 gene. These women were identified from 40 participating clinical cancer geneti...

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“…The inconsistencies in the reported effects of coffee or caffeine intake are largely attributed to methodological defects and failure to control for confounding variables, including baseline BP, smoking, gender, dietary and alcohol intake, stress, obesity, and inaccurate determination of daily coffee or caffeine intake. 20,21 The combination of regular coffee or caffeine consumption and psychological (eg, type A behavior pattern) and environmental (eg, job strain) factors may substantially influence ABP, 22 as was recently reported.…”

Section: Discussionmentioning

confidence: 99%

Effects of Coffee on Ambulatory Blood Pressure in Older Men and Women

1999

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Abstract-This study assessed the effects of regular coffee drinking on 24-hour ambulatory blood pressure (ABP) in normotensive and hypertensive older men and women. Twenty-two normotensive and 26 hypertensive, nonsmoking men and women, with a mean age of 72.1 years (range, 54 to 89 years), took part in the study. After 2 weeks of a caffeine-free diet, subjects were randomized to continue with the caffeine-free diet and abstain from caffeine-containing drinks or drink instant coffee (5 cups per day, equivalent to 300 mg caffeine per day) in addition to the caffeine-free diet for a further 2 weeks. Change in systolic and diastolic blood pressures (SBP, DBP) determined by 24-hour ambulatory BP monitoring showed significant interactions between coffee drinking and hypertension status. In the hypertensive group, rise in mean 24-hour SBP was greater by 4.8 (SEM, 1.3) mm Hg (Pϭ0.031) and increase in mean 24-hour DBP was higher by 3.0 (1.0) mm Hg (Pϭ0.010) in coffee drinkers than in abstainers. There were no significant differences between abstainers and coffee drinkers in the normotensive group for 24-hour, daytime, or nighttime SBP or DBP. In older men and women with treated or untreated hypertension, ABP increased in coffee drinkers and decreased in abstainers. Restriction of coffee intake may be beneficial in older hypertensive individuals. (Hypertension. 1999;33:869-873.)Key Words: coffee Ⅲ blood pressure, ambulatory Ⅲ aged Ⅲ controlled trial E levated blood pressure (BP) is a risk factor for the development of cardiovascular disease and may be exacerbated by regular consumption of coffee. Some crosssectional 1 and randomized, controlled studies 2,3 suggest an association between coffee drinking and increased BP, possibly due to caffeine. 4,5 After abstinence from coffee 6 or caffeine 7 for at least 12 hours, acute ingestion of caffeine increases BP and decreases heart rate (HR). With continued coffee or caffeine intake, tolerance develops, usually within 2 to 3 days, even in former caffeine nonusers. 8 Although no significant association between long-term caffeine or coffee intake and BP was found in some controlled trials in young and middle-aged 9,10 normotensive 11 and untreated hypertensive individuals, 12 other studies have reported short-and long-term pressor effects. [13][14][15] In a study that used ambulatory BP monitoring (ABPM), young mildly hypertensive men who were regular coffee drinkers had 2 to 3 mm Hg higher daytime systolic ambulatory BP (ABP) than nondrinkers. 16 However, there have been few studies in older men and women, 17 whose cardiovascular system is more likely to have an impaired ability to buffer pressor stimuli. One controlled study showed that chronic caffeine ingestion by elderly subjects had no significant effect on clinic or 24-hour BP levels, irrespective of BP status. 17 The present study aimed to assess, in a controlled 2-week intervention, the effects of regular coffee drinking on ABP in normotensive or hypertensive, nonsmoking older men and women, with careful control of dieta...

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Confounders contributing to the reported associations of coffee or caffeine with disease

Cited by 75 publications

References 26 publications

Coffee Acutely Increases Sympathetic Nerve Activity and Blood Pressure Independently of Caffeine Content

Coffee Acutely Increases Sympathetic Nerve Activity and Blood Pressure Independently of Caffeine Content

Coffee consumption and breast cancer risk among BRCA1 and BRCA2 mutation carriers

Effects of Coffee on Ambulatory Blood Pressure in Older Men and Women

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