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The systemic manifestations of Sjogren's syndrome at the time of diagnosis differ according to individual patient characteristics such as sex, age, and ethnicity, a large international study found.

Analysis of data from the Sjogren Big Data Consortium showed that the total mean score on the European League Against Rheumatism (EULAR) Sjögren's Syndrome Disease Activity Index (ESSDAI) was 8.1 among men compared with 6 for women (P<0.001), according to Manuel Ramos-Casals, MD, of the University of Barcelona, and colleagues.

And the mean ESSDAI was significantly higher for those diagnosed before age 35 compared with those with disease onset after 65 (6.7 vs 5.6, P=0.001), the researchers reported in .

Sjogren's syndrome is a systemic autoimmune disease primarily afflicting middle-age women that is characterized by lymphocytic infiltration of the exocrine glands (salivary and lachrimal), immunological abnormalities such as anti-Ro antibodies, and, in many cases, extraglandular involvement.

The team has also identified differences in the glandular features according to ethnicity and area of residence. "Since we have significant differences in the main Sjogren's syndrome-related glandular features between ethnic groups and geographical locations, it seems reasonable to analyze how systemic activity at diagnosis could also be modulated by geoepidemiological determinants," the investigators wrote.

The Sjogren Big Data Consortium was established in 2014, with data obtained from multiple centers in 22 countries throughout the world. Clinical variables recorded included age, sex, ethnicity, and country of residence, along with autoantibody profiles and organ-specific ESSDAI scores.

The analysis included 10,007 patients, of whom 9,352 were women. Mean age at the time of diagnosis was 53. Systemic activity was present at baseline in 81.8%, and mean ESSDAI in the total cohort was 6.1. is defined as an ESSDAI of 5 or higher.

Not only did men have higher total ESSDAI scores than women, but they also fared significantly worse in several individual domains of the ESSDAI:

• Lymphadenopathy was present in 12.7% of men vs 8.3% of women (P<0.001)

• Glandular involvement, in 27% vs 21.1% (P<0.001)

• Pulmonary complications, in 14.2% vs 10.2% (P=0.001)

• Peripheral nervous system involvement, in 11.6% vs 5.6% (P<0.001)

• Central nervous system involvement, in 3.8% vs 1.8% (P<0.001)

With regard to ethnicity, 76.9% of patients were white, 13.9% were Asian, 5.8% were Hispanic, 1.4% were black/African-American, and the remainder were classified as "other."

The highest mean ESSDAI scores were in blacks (6.7), while scores were 6.5, 5.4, and 4.8 in whites, Asians, and Hispanics, respectively (P<0.001).

Blacks also had the greatest frequency of lymphadenopathy and involvement of the neurologic, biologic, and articular domains, while involvement of the glandular, cutaneous, and muscular domains was most common among whites. The highest frequency of involvement of the pulmonary, renal, and hematologic domains was observed among Asians, and the constitutional domain among Hispanics.

Differences also were seen according to patient country of residence, following a north-south gradient. For the Americas, this was divided into North or South America; for Europe, it was latitude greater or less than 50° N, and for Asia, it was latitude greater or less than 30° N.

ESSDAI scores according to geographic location were as follows:

• South vs North America, 5.2 vs 3.5 (P<0.001)

• Southern vs northern Europe, 7.4 vs 4.2 (P<0.001)

• Southern vs northern Asia, 6.4 vs 4 (P<0.001)

Patients in the southern regions also more often had high disease activity in at least one domain of the ESSDAI, at 8.9% vs 3.4% for the Americas, 9.9% vs 2.9% for Europe, and 9% vs 4% for Asia.

Ramos-Casals pointed out that men are much less frequently affected by Sjogren's syndrome, comprising only 7% of this cohort, but typically exhibit a more severe phenotype. This may reflect a delay in diagnosis among males, or genetic factors may be involved. Genetic variations also may contribute to the differences in disease manifestations according to ethnicity, the team noted.

have also found a north-south gradient in the prevalence of other autoimmune diseases, with a greater frequency in southern regions. Variable explanations for this have been proposed, including differences in environmental and lifestyle factors, seasonality, air pollution, metals in the soil, and the use of silicone breast implants. In addition, revealed that geographic differences in the oral microbiota also might influence the Sjogren's syndrome phenotype.

This analysis confirmed that individual patient factors including age, sex, ethnicity, and residence strongly affect the systemic manifestations of Sjogren's syndrome. "Both the type of organ affected and the severity of the involvement are modulated by these geoepidemiological factors, which should be considered as critical when a personalized follow-up is planned for a patient newly diagnosed with Sjogren's syndrome," the researchers concluded.

A limitation of the study, they said, was its retrospective design.

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