No association between socioeconomic status and risk of multiple sclerosis: A population-based incident case-control study in a developing country

Observed associations between indicators of socioeconomic status and risk of multiple sclerosis in Sweden are explained by a few lifestyle-related factors

BACKGROUND AND PURPOSE

The association between socioeconomic status (SES) and the risk of multiple sclerosis (MS) is unclear. The aim was to study whether a potential association between indicators of SES and MS risk in Sweden is explained by lifestyle/environmental factors.

METHODS

Using the Swedish MS registry and the Swedish patient registries, a register study was performed comprising all cases diagnosed with MS in Sweden between 1990 and 2018 (N = 24,729) and five randomly selected controls per case, matched by year and age at disease onset, sex and residential area at disease onset. Data from two matched case-control studies combined comprising data on environment/lifestyle factors (7193 cases, 9609 controls, inclusion period 2005-2018) were also utilized. For all participants, information regarding ancestry, formal education (available 1990-2018) and family income (available 1998-2018) was retrieved from the National Board of Health and Welfare.

RESULTS

The registry study revealed no association between education and MS risk, whereas an income exceeding the upper quartile was associated with lower MS risk compared to having an income in the lowest quartile (odds ratio 0.86, 95% confidence interval 0.82-0.90). These findings were replicated in the crude analyses of the case-control study. However, after adjustment for confounding, no association was observed between income and risk of MS.

CONCLUSIONS

Education and income were not associated with occurrence of MS after adjustment for a few lifestyle-related factors (smoking, alcohol consumption, body mass index and sun exposure habits), indicating that SES has no influence on MS risk besides its association with these lifestyle factors in the Swedish context.

Stressful life events and the risk of primary progressive multiple sclerosis: A population-based case-control study

BACKGROUND

The onset and presentation of primary progressive multiple sclerosis (PPMS) like any other autoimmune diseases can be triggered by unexpected lifetime stressful events, which require to be assessed in order to minimize our exposure to such events as much as possible.

OBJECTIVE

The aim of the present study was to determine the possible role of socioeconomic status (SES) and stressful events in PPMS development METHODS: The present population-based case-control study recruited PPMS cases and healthy controls from the general population during 2019-2020 in Tehran, Iran. Clinical diagnosis of cases was based on the 2017 McDonald criteria and confirmed by a neurologist. The selection of sex-matched controls from the same source population of cases was performed using the standard method of Random Digit Dialing (RDD). The study questionnaire was filled out over telephone interviews. Matched logistic regression was administered to estimate the adjusted and unadjusted odds ratio (OR) at 95% confidence intervals (CIs) adjusted for sex, age, and marital status using SPSS 23.

RESULTS

This study examined 146 PPMS cases and 294 controls. Mean ages (SD) for cases and controls were 46.97 (9.4) and 37.67 (6.12), respectively (P < 0.001). No stressful events over five years prior to the disease onset were associated with an increased risk of PPMS. Marriage (OR: 0.04; 95% CI (0.01- 0.37), P = 0.004), close family members' serious disease (OR: 0.10; 95% CI (0.02-0.60), P = 0.01), and being in debt (OR: 0.03; 95% CI (0-0.37), P = 0.006) were found to have a negative association with the risk of disease occurrence. Death of a loved one, family disruption, jail term, homelessness period, Conquer(national university entrance exam), death of spouse, getting fired from a job, joblessness, divorce, migration, close family members' suicide, and retirement were not associated with the risk of PPMS (P > 0.05). History of depression before the PPMS presentation was considerably associated with the incidence of PPMS (P < 0.001). Self-rated health status was scored noticeably lower by cases as compared with controls (P < 0.001). Participants with the paternal educational degree of guidance school showed a higher risk of PPMS by 2.83 time (OR: 2.83; 95% CI (1.02 - 7.80), P = 0.04) than participants with university educated fathers. In total, SES during adolescence did not indicate any association with the risk of PPMS (with the exception of levels 2 (P = 0.02) and 7 (P = 0.05)).

CONCLUSION

No stressful life events were identified as possible increasing risk factors for PPMS. Marriage, close family members' serious disease, and being in debt had a negative association with the disease risk. The history of depression may elevate the risk of PPMS. While the highest and lowest SES levels in adolescence were not remarkable determiners for PPMS, levels 2 and 7 had a positive association with the risk of PPMS. The maternal educational level was not an important factor; however, the paternal educational degree of guidance school as compared to university degree made individuals more susceptible to PPMS. Self-rated health status score was higher in controls.

Prevalence and incidence of multiple sclerosis in Ardabil, Northwest of Iran

BACKGROUND

Multiple sclerosis (MS) epidemiology is studies in many populations; however, studying populations with unique characteristics could provide opportunities to deepen the understanding of the underlying reason of the disease. In this regard, we aimed to study the epidemiology of MS in Ardabil, a province in northwest Iran, where the majority are of Iranian Azerbaijanis.

METHOD

A retrospective population-based study was conducted from 2008 to 2018 in Ardabil, based on the data of Iran's Ministry Of Health. Collected information includes sex, age, age at disease onset, education and type of MS. We used t-test to compare means and chi-square test to analyze the association among variables.

RESULTS

The total number of patients was 760 with 533 (70.13%) females and 227 (29.87%) males. The crude prevalence was 59.37 per 100,000 in 2018 (95% CI: 55.31, 63.73). The crude incidence rate was 7.65 per 100,000 in 2018 (95% CI: 6.28, 9.32). The most frequent educational level was high school diploma (38.36%). The relapsing-remitting (RR) form was the most frequent type of MS (48.16%). The F/M ratio was 2.92:1 and the mean onset age was 33.14 (95% CI: 31.56, 34.72) in 2018, significantly higher in males (P value= 0.01).

CONCLUSION

Ardabil is a medium risk zone of MS. The different ethnicity of its population, climate and environmental features, may explain the factors modulating the risk of MS in similar areas and present windows of opportunity to understand the causes of MS.

Do socioeconomic factors affect the prevalence of multiple sclerosis in Iran?

BACKGROUND

A rising trend for incidence of multiple sclerosis (MS) has been observed during the recent years in Iran. Several factors have been investigated as the reason, but socioeconomic determinants have been neglected. The present study aimed to investigate the relationship between Human Development Index (HDI), income and education and MS prevalence in the provinces of Iran.

METHODS

The data used in this study were obtained from three sources: (a) National Registry of MS for MS prevalence data from 2006 to 2013, (b) Statistical Centre of Iran for demographic, income, and percentage of educated people data, and (c) some previous studies for HDI data.

RESULTS

The findings showed high prevalence of MS in the provinces of Iran. Most patients were residents of provinces with a higher socioeconomic level. Significant relationships were found between the prevalence of MS and HDI, income and educational level (P = .002, P = .006, and P = .001, respectively).

CONCLUSION

Socioeconomic determinants in Iran are different from those in many other countries. It seems that Iranian provinces with a higher socioeconomic level have higher prevalence of MS. Further studies in smaller scale are needed to better understand the relationship between socioeconomic determinants and MS prevalence in the provinces of Iran.