Study Title and Description
Coffee, caffeine, and risk of completed suicide: results from three prospective cohorts of American adults.
Key Questions Addressed
|1||For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on behavior*?|
Primary Publication Information
|Title||Coffee, caffeine, and risk of completed suicide: results from three prospective cohorts of American adults.|
|Author||M Lucas,EJ O'Reilly,A Pan,F Mirzaei,WC Willett,OI Okereke,A Ascherio,|
Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Behavior - Design Details - INCLUDED Studies
No arms have been defined in this extraction form.
|Question... Follow Up||Answer||Follow-up Answer|
|What outcome is being evaluated in this paper?||Behavior|
|What is the objective of the study (as reported by the authors)?||To evaluate the association between coffee and caffeine consumption and suicide risk in three large-scale cohorts of US men and women.|
|Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods)||We accessed data of 43,599 men enrolled in the Health Professionals Follow-up Study (HPFS, 1988–2008), 73,820 women in the Nurses’ Health Study (NHS, 1992–2008), and 91,005 women in the NHS II (1993–2007). To identify a healthy population, we excluded participants with diagnoses of cardiovascular disease or cancer at baseline. The main analyses in the present report use 1992 as the baseline for NHS because a previous report has been published on coffee and suicide risk between 1980 and 1990 (Kawachi et al. 1996). After exclusions, data from 43,599 HPFS, 73,820 NHS and 91,005 NHS II participants were available for analysis. Consumption of caffeine, coffee, and decaffeinated coffee, was assessed every four years by validated food-frequency questionnaires. Deaths from suicide were determined by physician review of death certificates. Multivariate adjusted relative risks (RRs) were estimated with Cox proportional hazard models. Cohort specific RRs were pooled using random-effect models.|
|How many outcome-specific endpoints are evaluated?||1|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||suicide risk|
|List additional health endpoints (separately).|
|List additional health endpoints (separately)|
|What is the study design?||Cohort|
|Randomized or Non-Randomized?|
|What were the diagnostics or methods used to measure the outcome?||Objective|
|Optional: Name of Method or short description||Physicians reviewed death certificates to classify individual causes of death. The end point of our study comprised all cases of suicide and self-inflicted injuries.|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||high vs low consumption (< 100 mg/day caffeine)|
|What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods)||In the multivariate analysis, we simultaneously controlled for potential confounders using updated information at each 2-year questionnaire cycle, including smoking status (never smoked, past, currently smoke 1 to 14, 15 to 24, or ≥25 cig./day), high alcohol consumption (≥30 g/day, <30 g/day), body-mass index (<25.0, 25.0 to 29.9, ≥30.0 kg/m2), physical activity (quintiles), marital status (married/partnered, widowed, separated/divorced/single), and reported regular use of antidepressants (yes or no), and minor tranquilizers such as benzodiazepines (yes or no). In NHS II, hormonal status (post-menopausal with or without hormonal therapy, pre-menopausal or never used hormonal therapy) was also included. Sensitivity analyses including factors that can mediate the effects of coffee, such as self-reported high blood pressure, myocardial infarction or angina, stroke, diabetes, and cancer (all yes/no) were preformed. Since caffeine half-life is reduced by 30–50% in smokers and doubled in women taking oral contraceptives or other exogenous estrogens (Fredholm et al. 1999), we examined effect modification by these factors of the caffeine/coffee and suicide associations.|
|Provide a general description of results (as reported by the authors).||Compared to those in the lowest (<100 mg/day) category of caffeine intake, the pooled multivariate RR of suicide was 0.54 (95% CI: 0.30, 0.94) for those with intake between 400 to 550 mg/day and 0.63 (95% CI: 0.39, 1.04; P for trend=0.005) for those with intake ≥550 mg/day (Table 3). For each increment of 300 mg of caffeine per day, the pooled multivariate RR for suicide was 0.77 (95% CI: 0.63, 0.93).|
|Did the authors perform a dose-response analysis (or trend/related analysis)?||Yes|
|What were the authors's observations re: trend analysis?||Compared to those in the lowest (<100 mg/day) category of caffeine intake, the pooled multivariate RR of suicide was 0.54 (95% CI: 0.30, 0.94) for those with intake between 400 to 550 mg/day and 0.63 (95% CI: 0.39, 1.04; P for trend=0.005) for those with intake ≥550 mg/day (Table 3).|
|What were the author's conclusions?||Overall, these results suggest that there is little further benefit for consumption above 2–3 cups/day or 400 mg of caffeine/day. Therefore, the continuous estimate should be interpreted with caution. The results of our study corroborate a lower suicide risk among coffee drinkers, and identify caffeine as the most likely candidate of any putative protective effect of coffee. The robustness of our findings supports, but does not prove, a protective effect of caffeine.|
|What were the sources of funding?||Supported by research grants P01 CA087969, U19 CA055075, and R01 CA050385 from the National Institutes of Health (NIH) for the maintenance and follow-up of the cohorts that provided data for the study. Dr. Ascherio is supported by NIH Grant R01 NS061858. Dr. Lucas received a postdoctoral fellowship from Fonds de recherche en santé du Québec (FRSQ).|
|What conflicts of interest were reported?||The authors have no conflict of interest to declare.|
|Does the exposure (dose) need to be standardized to the SR?||No|
|Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).|
|List all the endpoint(s) followed by the dose (mg) which will be used in comparison to Nawrot. Characterize value as LOAEL/NOAEL, etc. if possible.||suicide risk - NOAEL = 300 mg/day caffeine|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||caffeine had a protective role against suicide at levels lower than Nawrot.|
|What is the importance of the study with respect to the adverseness of the outcome?||Critcal|
No baseline characteristics have been defined for this extraction form.
Results & Comparisons
No Results found.
|Arm or Total||Title||Description||Comments|
No quality dimensions were specified.
No quality rating data was found.