drink coffee and live longer

An analysis of the Nurses' Health Studies (NHS, which began in 1976 with RNs aged 30-55 and  NHS2 which began in 1989 with RNs aged 25-42) and the Health Professionals Follow-up Study (HPFS, which began in 1986, with male health professionals aged 40-75) assessed total and cause-specific mortality in drinkers of caffeinated and decaffeinated coffee (see coffee and mortality circ2015 in dropbox, or DOI: 10.1161/CIRCULATIONAHA.115.017341). details:

--74,890 women in NHS, 93,054 women in NHS2, and 40,557 men in HPFS, with extensive semi-quantitative food frequency questionnaires (131 items, administered every 4 years), and 4,690,072 person-years of follow-up. 95% white.

--up to 30 years of follow-up, with extensive data on known or suspected confounders (biennial questionnaires asking about age, weight, smoking, physical activity, medication use, fam history of diabetes, and self-reported diagnoses including hypertension, hypercholesterolemia, cardiovasc disease, and cancer), and 31,956 deaths

--results:

    --never coffee drinkers, included 12% of those in NHS, 30% in NHS2, and 17% in HPFS

    --drinkers of >5 cups/d, included 24% of those in NHS, 35% in NHS2, and 25% in HPFS

    --compared to non-drinkers, coffee consumption of 1-5 cups/d was associated with decreased total mortality ( HR for death was 0.95 for <=1cup/d, 0.91 for 1.1-3 cups/d, 0.93 for 3.1-5 cups/d, all of which were statistically significant, and a nonsignificant HR of  1.02 for >5 cups/d). no diff between caffeinated and decaffeinated coffee consumption

    --when analysis was restricted to never smokers (there were 10,505 deaths in 2,451,970 person-years in this group), compared to nondrinkers:

            --<=1cup/d, HR for mortality 0.94 (0.89-0.99) 

            --1.1-3 cups/d, HR for mortality 0.92 (0.87-0.97)

            --3.1-5 cups/d, HR for mortality 0.85 (0.79-0.92) 

            -->5 cups/d, HR for mortality 0.88 (0.78-0.99) 

            --overall p<0.001 for the trend

            --the association with total mortality was especially strong for those <70yo; no differences if stratify by diet quality (they calculated the Alternate Healthy Eating Index), BMI, physical activity, sex, and the cohort studied (NHS vs HPFS)

            --for caffeinated coffee, the trend had p<0.001. for decaffeinated coffee, the trend had p=0.022 (still significant)

            --association with 1-cup increments of coffee/d found significant inverse associations for cardiovascular disease, neurological diseases, and suicide. no significant association with total cancer mortality

so, really great news...

--why does this make sense, especially since the association was not really with caffeine?

    --for cardiovascular disease: chlorogenic acid, lignans, quinides, trigonelline, and magnesium in coffee reduce insulin resistance and systemic inflammation

    --for neurological diseases (other studies have also found coffee consumption was associated with lower risk of Parkinson's): for MPTP-induced Parkinson's, there is loss of striatal dopamine transporter binding sites, and dopaminergic neurons, which is attenuated by caffeine

    --for suicides (also found in other studies): ???coffee has antidepressant effects, also it turns out that mice in stressful situations given caffeine have less stress-induced changes in their brains and behavior, but this doesn't really answer the question about coffee or esp about decaffeinated coffee in humans

--and, unfortunately, this study just reveals an association, so hard to say that this is causal. though this was based on really longterm studies of people with extensive food diaries and controlling for many of the underlying possible confounders (and, perhaps the major confounder of smoking). but, then again, it is all self-reported/not verified, and is in a largely white population of professionals, limiting the generalizability of its conclusions.

--but, at least coffee is not being demonized as being bad for your health..... in fact, it probably should be added to the food pyramid, and at the bottom (right next to the dark chocolate).