Caffeinated and decaffeinated coffee consumption and risk of type 2 diabetes: a systematic review and a dose-response meta-analysis.
OBJECTIVE
Previous meta-analyses identified an inverse association of coffee consumption with the risk of type 2 diabetes. However, an updated meta-analysis is needed because new studies comparing the trends of association for caffeinated and decaffeinated coffee have since been published.


METHODS
PubMed and Embase were searched for cohort or nested case-control studies that assessed the relationship of coffee consumption and risk of type 2 diabetes from 1966 to February 2013. A restricted cubic spline random-effects model was used.


RESULTS
Twenty-eight prospective studies were included in the analysis, with 1,109,272 study participants and 45,335 cases of type 2 diabetes. The follow-up duration ranged from 10 months to 20 years. Compared with no or rare coffee consumption, the relative risk (RR; 95% CI) for diabetes was 0.92 (0.90-0.94), 0.85 (0.82-0.88), 0.79 (0.75-0.83), 0.75 (0.71-0.80), 0.71 (0.65-0.76), and 0.67 (0.61-0.74) for 1-6 cups/day, respectively. The RR of diabetes for a 1 cup/day increase was 0.91 (0.89-0.94) for caffeinated coffee consumption and 0.94 (0.91-0.98) for decaffeinated coffee consumption (P for difference = 0.17).


CONCLUSIONS
Coffee consumption was inversely associated with the risk of type 2 diabetes in a dose-response manner. Both caffeinated and decaffeinated coffee was associated with reduced diabetes risk.
Corresponding author: Frank B. Hu, nhbfh@channing.harvard.edu.
Ming
M
Ding
Shilpa N
SN
Bhupathiraju
Mu
M
Chen
Rob M
RM
van Dam
Frank B
FB
Hu
D002110:Caffeine / Q000008:administration & dosage*; D003069:Coffee; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D011795:Surveys and Questionnaires
D003069:Coffee; D002110:Caffeine