We restricted this assessment to the broad mortality combinations as sufficient estimates were available.
The few available estimates were mainly limited to the broad mortality combinations and, with the exception of all-cause mortality, gave comparable summary estimates (table 2).
Evidence of high heterogeneity in WHO region-specific summary estimates was identified in more than half of the mortality combinations (table 2 and see online supplementary table S1).
Where available, summary estimates for WHO region America A, that is, USA and Canada, were consistently smaller than those from other WHO regions for all mortality combinations examined for 24 h NO2.
While the presence of heterogeneity and the small number of studies for each risk factor-outcome comparison limited the ability to assess the risk of publication bias, there was no convincing evidence of publication bias for the risk factor-mortality combinations that were deemed to be at low level of evidence.
We have elaborated a population projection for the next 50 years using in the case of mortality a combination of probabilistic projection, an improved method originally proposed by Lee-Carter, and with scenario construction in the case of fertility.
Fig. 3 Outcomes (30-day mortality and/or combination of ICU transfer) according to levels of PCT.
The hazard ratios (HRs) for 28-day mortality for combination therapy were 0.62 (95% CI 0.40 0.98, P = 0.043 [Cox's proportional hazards model) and 0.55 (95% CI 0.34 0.89, P = 0.014 [propensity score matching]), and significant associations were observed between the combination therapy and a lower 28-day mortality (Table 3).
Multivariable analysis identified only distant metastases (OR =4.6) as independently associated with increased mortality, whereas combination therapy (OR =0.4) was associated with reduced mortality, P<0.005.
The estimated RRs were >1.0 in all subgroups except for the association between all-cause mortality and combination therapy compared with sulfonylurea.
