A large observational study found a significant inverse relationship between consuming caffeine and all-cause mortality among US patients with chronic kidney disease (CKD). The research was published online September 12 in Nephrology Dialysis Transplantation.
Previous research has found an inverse relationship between consuming coffee and all-cause mortality in the general population. However, the effect of caffeine in individuals with CKD has been unclear.
In the current study, Miguel Bigotte Vieira, MD, from the Nephrology and Renal Transplantation Department at Centro Hospitalar Lisboa Norte in Lisbon, Portugal, and colleagues analyzed data from 4863 persons drawn from the National Health and Nutrition Examination Survey from 1999 to 2010.
Survey participants completed detailed interviews at home, then took part in telephone interviews about dietary habits. They also underwent physical examinations that included measurements of height and weight, as well as laboratory testing.
Vieira and colleagues tapped recollections of food and beverages consumed in the prior 24 hours to calculate the amount of caffeine that participants consumed from coffee, tea, and soft drinks. They stratified participants into quartiles by caffeine intake. During the 60-month median follow-up period (27,724 total person-years), 1283 participants (26%) died.
Compared with those who consumed no caffeine, any consumption was associated with approximately a 25% reduction in risk, but increasing consumption was not associated with the increased benefit.
Specifically, for those in the lowest consumption group, the adjusted hazard ratio was 0.74 (95% confidence interval [CI], 0.60 – 0.91), compared with no consumption.
For the third and fourth quartiles of consumption, the hazard ratios were 0.75 (95% CI, 0.61 – 0.92) and 0.75 (95% CI, 0.59 – 0.97; P = .02, for trend), respectively.
"There was no significant interaction between caffeine consumption quartiles and CKD stages regarding all-cause mortality," Vieira and coauthors write.
Those with the highest caffeine intake were more likely to be male, non-Latino whites, have higher education levels and higher annual incomes, and were more likely to be current or former smokers who consumed more alcohol.
The research team also found an unexpected inverse relationship between consuming caffeine via soft drinks and all-cause mortality in patients with CKD. The study authors write that because an estimated 89% of US adults consume caffeine daily, their findings could have a significant impact on public health.
"Considering the mean caffeine content per unit of caffeinated beverage (95 mg in 8 oz of coffee, 48 mg in 8 oz of tea and 30 mg in 12 oz of cola), even small quantities of commonly consumed beverages may confer a protective effect regarding all-cause mortality in patients with CKD," the researchers conclude. "However, the mechanism that confers the protective effect of caffeine consumption is uncertain."