Coffee Drinking Tied to Better Survival, but Timing Matters

Any presumed health benefits of coffee may be limited to morning cups of joe, according to an observational study based on the National Health and Nutrition Examination Survey (NHANES).

Compared with non-coffee drinkers, those who mostly drank coffee in the morning had a lower risk of all-cause mortality (adjusted HR 0.84, 95% CI 0.74-0.95) and cardiovascular mortality (HR 0.69, 95% CI 0.55-0.87) when followed over a median 9.8 years.

It appeared that survival was particularly improved with morning consumers drinking moderate (>1 to 2 cups and >2 to 3 cups/day) and heavy (>3 cups/day) amounts of coffee rather than lesser amounts, reported Lu Qi, MD, PhD, epidemiologist of Tulane University in New Orleans and Harvard T.H. Chan School of Public Health in Boston, and colleagues in European Heart Journal.

In contrast, people who kept drinking coffee later in the day, the all-day type, had no reduction in all-cause mortality (HR 0.96, 95% CI 0.83-1.12) and cardiovascular mortality (HR 0.82, 95% CI 0.61-1.10) regardless of how much they consumed.

Neither coffee drinking pattern was tied to more or less cancer-specific mortality.

“We found that coffee drinking timing was associated with all-cause mortality risk and [cardiovascular disease]-specific mortality risk independent of the amounts of coffee intake,” Qi’s group concluded. “Our findings highlight the importance of considering drinking timing in the association between the amounts of coffee intake and health outcomes.”

The authors suggested two potential mechanisms that could explain their findings. One is that all-day caffeine consumption can disrupt circadian rhythms. Secondly, there may be anti-inflammatory substances within coffee that can counteract the body’s pro-inflammatory cytokines when they are typically at their highest levels in the morning.

“Why would time of the day matter? In the morning hours there is commonly a marked increase in sympathetic activity as we wake up and get out of bed, an effect that fades away during the day and reaches its lowest level during sleep. Thus, it is possible, as the authors point out, that coffee drinking in the afternoon or evening disrupts the circadian rhythm of sympathetic activity,” agreed Thomas Lüscher, MD, cardiologist of Royal Brompton and Harefield Hospitals in London and the University of Zurich, writing in an accompanying editorial.

Previously, multiple observational studies had shown that moderate coffee consumption has an inverse association with mortality risk and risk of type 2 diabetes and other chronic conditions. At the same time, the data are mixed regarding heavy coffee consumption.

None of the work so far can establish causal relationships between coffee drinking and survival.

“We don’t typically give advice about timing in our dietary guidance, but perhaps we should be thinking about this in the future,” Qi nevertheless said in a press release. “Further studies are needed to validate our findings in other populations, and we need clinical trials to test the potential impact of changing the time of day when people drink coffee.”

That may be easier said than done, however. “[T]hese cohorts are not randomized trials, probably as nobody wanted to be in the placebo group … Be that as it may, it is unlikely that we will see a large, randomized trial over prolonged periods of time,” Lüscher wrote.

“Overall, we must accept the now substantial evidence that coffee drinking, particularly in the morning hours, is likely to be healthy,” he urged. “Thus, drink your coffee, but do so in the morning!”

Qi and colleagues performed their study using the 1999-2018 cycles of NHANES, a nationally representative cohort that includes health exams and lab tests. There were 40,725 adult participants identified who had completed 24-hour dietary recalls.

Reported coffee habits were fed into a cluster analysis that split participants into morning type (36%) and all-day types (16%) of coffee drinkers, the remainder considered non-coffee drinkers. These coffee drinking patterns were validated in 1,463 adults from the Women’s and Men’s Lifestyle Validation Study who had complete data on 7-day dietary records.

Compared with non-coffee drinkers, the morning and all-day types were older, more likely to be white, had higher family income, and a higher prevalence of diabetes, hypertension, and high cholesterol. Among coffee drinkers, the morning-type pattern was associated with more tea and caffeinated soda drinking but lower overall quantities of coffee than the all-day pattern.

The authors tried to adjust their mortality analyses to account for between-group differences in caffeinated and decaffeinated coffee intake amounts, sleep hours, and other confounders.

“Indeed, it is possible that coffee drinkers differ from non-drinkers in many aspects,” Lüscher cautioned. “Of note, dietary and lifestyle habits, in particular smoking, may affect any of the observed associations. Some may work against the hypothesis provided in the current study as coffee drinkers are more likely to smoke than non-drinkers. This may particularly be the case of all-day drinkers who may be somewhat more addicted to this habit that may annihilate the protective effects of coffee drinking.”

Other limitations to the study include the possibility of recall bias and measurement errors. Whether the findings can be generalized to other countries and other cultures is unknown.

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