Routine examinations of patients with primary Sjögren’s syndrome should include cognitive function tests to assess the presence of impairments, a review study recommends.
The study, “Cognitive Function in Primary Sjögren’s Syndrome: A Systematic Review,” was published in Brain Sciences.
Sjögren’s syndrome is a chronic autoimmune disease characterized by abnormal infiltration and accumulation of immune cells inside some glands, leading to tissue inflammation and eventually irreparable damage. As a result, patients affected by the condition usually experience extreme dryness in the eyes and mouth.
The disorder is considered primary (pSS) when there is no underlying cause, or secondary when it occurs together with other autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus.
“At least one-third of patients with pSS can present with extraglandular involvement, with neurological dysfunction being one of the most frequent conditions… In 25–60% of cases, neurological symptoms are the first clinical manifestation and can precede the diagnosis of pSS on an average of two years,” the scientists wrote.
This review study focused on summarizing the main findings of published studies assessing the incidence and type of cognitive impairments reported in pSS patients, with a particular emphasis on the diagnostic methods used and their relationship with laboratory data and clinical symptoms of the disease.
Literature searched in three online databases — Medline, Embase, and PsycINFO — yielded a total of 352 potentially relevant studies published from 2002 10 2018. After further screenings, a total of 21 studies (one retrospective study, one population-based study, two prospective studies, three case reports, and 13 case-control studies) involving 6,196 pSS patients were selected to be included in the review.
From the 21 studies included in the review, six reported a relationship between pSS, mild cognitive impairment and dementia. In most studies reporting the occurrence of cognitive impairments in pSS patients, the most common symptoms included brain fog and mild cognitive impairment.
The link between pSS and neurological dementias, such as Alzheimer’s disease, was highly controversial, even though some studies argued that pSS might be a risk factor for the development of these disorders.
Most studies included in the review presented at least one major drawback, including:
- Failing to assess and/or report the severity of pSS, and consequently, not being able to draw any solid conclusion on the possible relationship between disease severity and cognitive deficits;
- Not taking into account the impact of other disease comorbidities;
- Lacking information about the particular type of dementia observed;
- Failing to assess or find any relevant correlation between extraglandular manifestations of pSS, laboratory data and cognitive dysfunction.
Despite these limitations, this review highlighted four aspects that should be taken into account by physicians caring for pSS patients:
- Dementia may occur in pSS patients; although older age seems to be the major risk factor for dementia, in a small percentage of the cases (5%) it also may be directly associated with pSS;
- pSS patients may have reversible autoimmune-induced dementia, which, if misdiagnosed as neurodegenerative dementia, might lead to serious consequences;
- Brain magnetic resonance imaging (MRI) scans showing no abnormalities are common in pSS patients;
- Cognitive deficits may be one of the first symptoms of pSS for some patients.
“Hence, it is very important that clinicians look for sicca syndrome or for laboratory data suggestive of pSS when direct observation and neurologic tests detect problems with information processing, attention, memory, or executive function, even if brain MRI is normal or in the presence of a few [small brain lesions],” the researchers wrote.
“This systematic review confirmed that adequate studies on cognitive function in pSS are scarce, mostly performed on small-sized samples, and often conflicting. The routine assessment of cognitive function in patients with pSS seems advisable and it will help to elucidate some of the unmet needs highlighted by this review in future appropriately designed studies,” they added.
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