Neurological comorbidity and severity of COVID-19

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), declared a pandemic on 11 March 2020 [1]. Clinical features range from the absence of symptoms to severe respiratory failure [2]. A rapidly increasing number of articles have been published on COVID-19, including numerous reports and studies on associated neurological symptoms and complications [3], such as acute stroke [4], hyposmia [5], Guillain–Barrè syndrome [6], encephalitis [7]. It has been shown that about one-third of COVID-19 patients develop neurological symptoms [3, 8], in most cases associated with a more severe infection [3], indicating a potential neurotropism of SARS-CoV-2 as one of the possible mechanisms of neurological damage [9, 10]. A recent retrospective study reported that inpatients from a neurological ward affected by COVID-19 showed a worse outcome compared to those infection-free [11]. However, no data have been reported yet on the prevalence and the association with infection severity of pre-existing neurological comorbidities in COVID-19 patients. A scoping review on the occurrence of neurological diseases in COVID-19 patients reported a prevalence of about 8% [12]. Nevertheless, this review highlighted the methodological heterogeneity in the reviewed papers, which limit a reliable estimation of prevalence of neurological diseases in COVID-19 patients, as well as their association with the infection severity.

The aim of our study was to evaluate, on a large cohort of consecutive patients admitted to the Emergency Room (ER) and diagnosed with COVID-19, the prevalence of neurological comorbidities and their possible association with a more severe form of COVID-19 onset.

We evaluated all consecutive patients admitted to the ER of the “Città della Salute e della Scienza di Torino Hospital” between 3 March 2020 and 14 April 2020, and diagnosed with COVID-19 by means of a positive Reverse Transcription Polymerase Chain Reaction nasopharyngeal swab.

The main demographic and clinical features of 344 consecutive patients evaluated are summarized in Table 3.

The mean age of the entire sample was 61.5 years: 4.7% of patients were ≤30-year-old, while 33.7% were ≥70-year-old. Male accounted for 59.3% of cases. The mean latency between the symptoms’ onset and the ER admittance was 6.1 days, ranging from 0 to 30 days; only two patients (0.6%) with mild symptoms (sore throat and sporadic cough) had a latency of 30 days, while 91.6% of patients were evaluated within 10 days from the onset, and 7.8% between 11 and 15 days. The most frequent symptom at COVID-19 onset was fever (74.1%; n = 255; isolated in 100 patients, associated with ≥1 other symptoms in 155 patients), followed by cough (44.8%; n = 154), dyspnea (13.7%; n = 47), and diarrhea (9.3%; n = 32). The majority of patients reported a monosymptomatic onset (52.0%; n = 179), while 36.3% (n = 125) presented with two symptoms, and 11.6% (n = 40) with three or more symptoms. Thirty-four percent of cases (n = 118) entered the ER with a severe form of infection.

Arterial hypertension was the most frequent comorbidity (45.9%), followed by neurological diseases (22.4%), neoplastic diseases (14.2%), diabetes (12.2%), chronic obstructive pulmonary disease (COPD) (11.9%), and renal failure (5.2%).

None of the patients were treated with specific antiviral drugs before admission; 9 of them (2.6%) were on hydroxychloroquine therapy (200 mg bid; therapy duration 5.2 ± 2.6 days, range 1–10).

In this study, we evaluated the prevalence of neurological pre-existing comorbidities in a large cohort of patients admitted to ER and diagnosed with COVID-19, estimating their association with infection severity. Over 20% of patients presented with neurological comorbidities, with cerebrovascular disease and cognitive impairment being the most frequent. Patients with neurological comorbidity showed an OR of 2.3 of suffering from severe COVID-19, even after including age and other clinical and demographic characteristics in the multivariate analysis. This association was stronger when patients suffering from a neurological condition in association with other comorbidities were compared to patients with isolated neurological or non-neurological diseases. Cerebrovascular diseases and cognitive impairment showed higher rate of severe infection and respiratory support indication, and lower rate of discharge at home.

To date, the incidence of new-onset neurological symptoms or syndromes associated with COVID-19 has been reported [3‐8], but the description of the relationship between pre-existing neurological comorbidities and infection severity still lacks. A recent review by Herman and colleagues reported a pooled prevalence of neurological comorbidities of 8% among 22 reviewed studies (range 0–40%), without conclusive data on the association with infection severity [12]. A recent study on inpatients from a neurological ward [11], showed worse clinical and functional outcomes, a more frequent use of high-flow oxygenation and antibiotic/antiviral treatments, longer hospitalization, and higher in-hospital mortality rate in patients with neurological diseases and COVID-19, compared to patients without infection; the vast majority of patients with COVID-19 were hospitalized for acute cerebrovascular events. Moreover, a meta-analysis reported that pre-existing cerebrovascular diseases could be an independent risk factor for COVID-19 [15]. In small-sample studies, cerebrovascular diseases have been associated with more frequent ICU admission [16] and with more severe forms of infection [17, 18]. In addition, Du and colleagues reported a 2.4-fold higher mortality risk in patients with cerebrovascular or cardiovascular disease, without specifying the distinction between these two conditions [19].

Our data show that patients with pre-existing cerebrovascular diseases are more frequently hospitalized, needing ICU admission in over 20% of cases, and present with a severe infection in two-thirds of cases. We observed similar findings in cognitively impaired/demented patients. A recent paper reported a prevalence of 6.8% of dementia in a sample of 355 Italian patients who died with COVID-19, without assessing the association with infection severity [20].

In our samples, we observed that patients suffering from neurological diseases were older, more affected by other comorbidities, and more institutionalized. Age is a frequently reported risk factor for severe COVID-19 [16, 19], as well as hypertension [21], diabetes [21, 22], neoplastic diseases [21, 23], COPD [21], and institutionalization [24]. These observations were confirmed in our study. The multivariate analysis showed that even correcting for age, institutionalization, and comorbidities, the presence of neurological diseases seems to be independently associated with a more severe form of infection. The strongest association with severe COVID-19 was observed in patients with both neurological diseases and other comorbidities. This finding is consistent with the results reported by Guan and colleagues, who found hazard ratios for worse infection outcomes as higher as the number of concomitant diseases increases [21]. On the other hand, institutionalization, diabetes, renal failure, and COPD showed a high association with infection severity only in the univariate analysis, but not in the multivariate analysis.

The higher prevalence of severe COVID-19 in patients affected by neurological diseases is probably multifactorial. The intrinsic frailty of chronic and often degenerative conditions, the older age, and the higher comorbidity burden observed in these patients could certainly explain this association [25]. Patients affected by neurological diseases could present a lower ability to compensate for COVID-19, resulting in more severe infection and higher need of ER assistance. Moreover, the potential neurotropism of SARS-CoV-2, with a possible detrimental effect on pre-existing neurological diseases, should also be taken into account [9, 10], as already postulated during the SARS-CoV epidemic in 2003 [26]. While waiting for more accurate pathological evidences, our data underline that patients with neurological diseases, in particular when associated with other comorbidities, represent a population at high risk for severe COVID-19, needing a careful health surveillance.

Our study presents with some limitations. First, the single-center design, which partially restricts the generalizability of our findings. Second, only a minority of patients suffered from neurological diseases without other comorbidities, limiting the conclusions on the association between neurological pathology alone and severe COVID-19. Third, the observations on the prevalence of each neurological disorder, and thus the ability to discriminate disease-specific associations with COVID-19, are limited by two factors: a) the evaluation of patients admitted to ER, which could represent a selection bias towards older people, and b) the lack of adjustments for the relative prevalence of each neurological disease in the general population.

In conclusion, our study reports the prevalence of different neurological diseases in a large cohort of patients with COVID-19, assessing their association with the infection severity. In our sample, patients with pre-existing neurological diseases showed a significantly higher risk for severe infection, in particular when associated with other comorbidities, suggesting that this population deserves a thorough evaluation since the earliest phases of overt or suspected COVID-19. Finally, our findings suggest a particular attention in targeting patients with neurological diseases for proactive viral screening.