I am reviewing a paper that seeks to assess the effect of treatment on mortality using observational data about 2,985 hospitalized patients. A propensity-matched analysis ends up with 380 patients (190 treated/190 not treated). But these 380 patients are a highly selected group compared with all 2,985 patients. For example, only 6.3% of the 380 patients in the propensity-matched analysis were admitted to the ICU compared with 24.2% of all patients; only 5.3% of the 380 the patients in the propensity-matched analysis were mechanically ventilated compared with 17.6% of all patients.

The literature on propensity-matched analyses identifies inefficiency/loss of power as a problem with propensity-matching. But isn't generalizability (the ability to draw conclusions about a causal effect of treatment on mortality in all of the hospitalized patients) also a concern?