There has been an exponential increase in the number of systematic reviews and meta-analyses in the past 40 or so years, writes Giovanni Domenico Tebala from Noble's Hospital in the UK in Medical Hypotheses.
Tebala worries, though, that researchers may devote themselves more to such meta-analyses at the expense of randomized controlled trials and clinical data. He notes that systematic reviews and meta-analyses are not as time-consuming or as expensive as randomized controlled clinical trials, but still can be published in high-impact journals.
According to his analysis, there are more than 10,000 systematic reviews and meta-analyses published each year, up from about 5,000 a year just two or three years ago.
"[I]f we are not able or willing to invert this trend — we will have less and less clinical data and more and more extrapolations of these data," Tebala says. He adds that "[i]f the scientific community is eager to get solid data and robust evidence, more systems should be in place to favor, with funding and rewards, basic and clinical researches and RCTs with respect to synthetic studies."
Blogger Neuroskeptic adds that as meta-analyses become more prevalent, "the scientific literature [will become] dominated by interpretation and analysis resting on a limited amount of evidence." That is, Neuroskeptic says, the pyramid of evidence will become top-heavy.