Reading the paper, it appears that there is, indeed, a statistical & effective difference between the coffee/caffeine drinking set and the non-drinking set.
It's also worth noting that these trials were targeted at senior citizens.
It appears they did check vs. aging effects.
However, there are limitations:
We also did not ask participants when their last caffeine intake was prior to coming in for the initial visit/blood sample. As well, we did not ask subjects about their long-term caffeine/coffee intake habits, although it is likely that subjects with high plasma caffeine levels are habitual/moderate coffee drinkers. Additionally, complete data on ApoE status, education level, ethnicity, dietary habits, and lifestyle choices were not available for all study participants, so none of these can presently be eliminated as contributory to the results observed. Finally, the follow-up time of 2–4 years was relatively short for establishing causality and reverse causation (i.e., subjects with poorer cognitive performance may have reduced caffeine/coffee intake) is
possible.
Essentially, they sampled twice and compared cognitive capabilities. However, there appears to be a existing body of knowledge indicating there is a strong linkage.
"Additionally, complete data on ApoE status, education level, ethnicity, dietary habits, and lifestyle choices were not available for all study participants, so none of these can presently be eliminated as contributory to the results observed."
It's also worth noting that these trials were targeted at senior citizens.
It appears they did check vs. aging effects.
However, there are limitations:
We also did not ask participants when their last caffeine intake was prior to coming in for the initial visit/blood sample. As well, we did not ask subjects about their long-term caffeine/coffee intake habits, although it is likely that subjects with high plasma caffeine levels are habitual/moderate coffee drinkers. Additionally, complete data on ApoE status, education level, ethnicity, dietary habits, and lifestyle choices were not available for all study participants, so none of these can presently be eliminated as contributory to the results observed. Finally, the follow-up time of 2–4 years was relatively short for establishing causality and reverse causation (i.e., subjects with poorer cognitive performance may have reduced caffeine/coffee intake) is possible.
Essentially, they sampled twice and compared cognitive capabilities. However, there appears to be a existing body of knowledge indicating there is a strong linkage.
http://health.usf.edu/nocms/publicaffairs/now/pdfs/JAD111781...