4.1 Key results
We observed that the pandemic period was independently associated with an increased likelihood of receiving LLST, and that this association was more pronounced among patients with COVID-19. The effects of key covariates on LLST also varied depending on COVID-19 status and the timing of the pandemic. (Supplement 4–9).
4.2 Increased likelihood of LLST in the COVID-19 period
The observed increase in LLST during the COVID-19 pandemic, although modest, suggests a shift in clinical practice and decision-making. The change over time, however, was surprisingly small. The reasons for this merit further discussion.
Before the pandemic, a larger proportion of patients had no documented LLST decision (“No Documented Decision”; Fig. 3). Because these cases were excluded from the analysis, LLST use before the pandemic may have been overestimated. During the pandemic, the number of patients with “No Documented Decisions” decreased, meaning that fewer such cases were excluded. Consequently, the observed increase in LLST use during the pandemic may appear smaller than it truly was, since part of the pre-pandemic LLST rate may reflect missing documentation rather than actual treatment limitation decisions. This interpretation aligns with findings by Jönson et al. (2022) [17], who reported similar survival among patients with “Full Care” and those with “No Documented Decision”, suggesting that the latter group may have been more comparable to “Full Care” than to LLST cases.
Another reason why the increase in LLST was only marginal in the ICU during the pandemic, may be a higher threshold for ICU admission due to actual or perceived bed shortages. As shown in Table 1, mean ICU occupancy was substantially higher during the COVID-19 pandemic, and higher LLST rates outside the ICU [18, 19] indicate that more patients were deemed “Not for ICU” during this period. Our study did not capture LLSTs for patients on general wards and could not adjust for this. In our multivariable analysis, ICU occupancy was not independently associated with LLST presence (Supplement 4 and 9).
Sotoodeh et al. (2025) studied 20,261 hospitalized Swedish patients and found that higher occupancy increased the likelihood of patients being ‘Not for ICU’ [20]. Since our analysis only included admitted patients, ICU occupancy likely influenced ICU admission decisions more than LLST use among those admitted. Limited ICU resources may have necessitated prioritizing patients with more severe acute conditions, raising ethical considerations. However, the mean SAPS3 score was similar before and during the pandemic (p = 0.64), suggesting that illness severity among admitted patients remained largely unchanged despite these pressures
4.3 COVID-19 status and the pandemic
During the COVID-19 pandemic period, we found a significantly increased risk of LLST among COVID-19 compared to non-COVID-19 patients (OR 1.17, 95%, CI 1.07–1.25). This somewhat contradicts findings from an Australian study [21], where frail patients with, compared to without, COVID-19 had the same frequency of LLST. As shown in our study, SAPS3 scores—used to predict hospital mortality at ICU admission—did not differ significantly before or during the pandemic, and only minimally between COVID-19 and non-COVID-19 patients (Tables 1 and 2).
Multiple studies demonstrated that the pandemic, and more specifically, COVID-19 status, had a significant but divergent impact on time to surgery and surgical outcomes [22, 23] and delayed or avoided acute care [24, 25, 26].
The mechanisms underlying the increased likelihood of LLST among COVID-19 patients remain unclear. Syrous et al. [27] examined end-of-life decision-making in critically ill elderly patients during the pandemic and found that LLST decisions in COVID-19 patients were influenced by different factors compared with non-COVID-19 patients. Similarly, the European multicenter COVID-ICU study [28] identified age, frailty, and early severity of respiratory failure as key determinants of LLST, with notable variation across centers. LLST was, as expected, strongly associated with higher mortality, highlighting a fundamental challenge for intensivists: whether LLST contributes to mortality, reflects the severity of illness, or represents a combination of both.
Although the overall rise in LLST was modest during the COVID-19 pandemic, the qualitative change in documentation practices—from 18.5% of patients lacking a recorded decision in 2018 to 11.4% in 2022, a 39% relative decrease (see Fig. 3)—may reflect a heightened ethical awareness, which would make it a sign of meaningful evolution. Future research could explore whether these changes have persisted beyond the acute phase of the pandemic and how they have impacted patient outcomes, staff experiences, and ethical climate in healthcare settings.
4.2 Strengths and Limitations
This is a nationwide registry study with strengths including high completeness and limited selection bias. Limitations include accuracy variations due to human error at registration and measurement bias due to variability in data completeness collections across different sites. There are limitations to the observational design with possible unmeasured confounders and residual confounding. Although we used DAGs and attempted to analyse mediation, such analyses rely on multiple assumptions that are difficult to meet, why the mediation analyses should be interpreted with caution.