Caffeinated Coffee Consumption and Health Outcomes in the US Population: A Dose-Response Meta-Analysis and Estimation of Disease Cases and Deaths Avoided

Abstract

To explore the role of coffee on health outcomes in the United States, where coffee consumption is common, we conducted a meta-analysis of prospective studies investigating the magnitude (any compared with no consumption) and the dose-response shape (cups per day) of the associations between caffeinated coffee consumption and incidence/mortality of cardiovascular disease (CVD), as well as incidence of type 2 diabetes (T2D), hepatocellular carcinoma (HCC), endometrial cancer, melanoma, and nonmelanoma skin cancer. We selected the desirable health outcomes that have been shown to be positively associated with coffee consumption. Studies were identified by searching PubMed/Embase databases up to September 2019. Inclusion criteria included prospective studies that investigated the relation of ≥3 categories of caffeinated coffee consumption and the outcomes of interest. Twenty-six studies (42 distinct cohorts), with 93,706 cases/deaths and 3,713,932 participants, met the inclusion criteria. In any coffee consumers, there was a significant inverse association with the risk of CVD (RR = 0.90; 95% CI: 0.84, 0.96), T2D (RR = 0.90; 95% CI: 0.85, 0.96), endometrial cancer (RR = 0.85; 95% CI: 0.78, 0.92), melanoma (RR = 0.89; 95% CI: 0.80, 0.99), and nonmelanoma skin cancer (RR = 0.92; 95% CI: 0.89, 0.95). Coffee consumption was also inversely associated with HCC (RR = 0.93; 95% CI: 0.80, 1.08), without reaching statistical significance. The dose-response relation was nonlinear uniquely for CVD (P-nonlinearity = 0.01). In particular, the largest risk reduction was observed for 3-4 cups/d (∼120 mL/cup) and no reduction thereafter. For other outcomes, the risk decreased linearly over the whole coffee consumption range. Current patterns of consumption in the United States would account for a fraction of avoided cases/deaths ranging from 6% to 12% according to the outcome considered. This study confirms the beneficial health effects of caffeinated coffee consumption in the US population on the health outcomes considered, and quantifies their possible magnitude.

Keywords: US population; attributable fraction; caffeinated coffee consumption; dose–response shape; health outcomes.

FIGURE 1

Flowchart of studies selection on caffeinated coffee consumption and selected outcomes.

FIGURE 2

Pooled adjusted RRs and corresponding 95% CIs (from random-effects meta-analysis) of cardiovascular disease incidence/mortality (A) and type 2 diabetes incidence (B) according to caffeinated coffee consumption (any vs. no consumption). United States, 1987–2017. exp, represented people with any consumption; Unexp, represented people with no consumption.

FIGURE 3

Pooled adjusted RRs and corresponding 95% CIs (from random-effects meta-analysis) of hepatocellular carcinoma incidence (A), endometrial cancer incidence (B), melanoma incidence (C), and nonmelanoma skin cancer incidence (D) according to caffeinated coffee consumption (any vs. no consumption). United States, 1987–2017. exp, represented people with any consumption; Unexp, represented people with no consumption. Note: results of the Liver Cancer Pooling Project (LCPP) depicted in (A) included the National Institutes of Health-American Association of Retired Persons (NIH-AARP) Diet and Health Study, Agricultural Health Study (AHS), United States Radiologic Technologists Study (USRTS), Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, Women's Health Study (WHS), Cancer Prevention Study-II (CPS-II) Nutrition Cohort, Iowa Women's Health Study (IWHS), Black Women's Health Study (BWHS), and Women's Health Initiative (WHI).

FIGURE 4

Pooled dose–response association (from 2-stage random-effects dose–response meta-analysis) between caffeinated coffee consumption (cups per day) and cardiovascular disease incidence/mortality (A) and type 2 diabetes incidence (B). United States, 1987–2017. Coffee consumption was modeled with restricted cubic spline. In the spline model, a binary term (consumption/no consumption) was added to take into account spike at zero for coffee.

FIGURE 5

Pooled dose–response association (from 2-stage random-effects dose–response meta-analysis) between caffeinated coffee consumption (cups per day) and hepatocellular carcinoma incidence (A), endometrial cancer incidence (B), melanoma incidence (C), and nonmelanoma skin cancer incidence (D). United States, 1987–2017. Coffee consumption was modeled with restricted cubic spline. In the spline model, a binary term (consumption/no consumption) was added to take into account spike at zero for coffee. Note: results of the Liver Cancer Pooling Project (LCPP) depicted in (A) included the National Institutes of Health-American Association of Retired Persons (NIH-AARP) Diet and Health Study, Agricultural Health Study (AHS), United States Radiologic Technologists Study (USRTS), Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, Women's Health Study (WHS), Cancer Prevention Study-II (CPS-II) Nutrition Cohort, Iowa Women's Health Study (IWHS), Black Women's Health Study (BWHS), and Women's Health Initiative (WHI).