In this cross -sectional study women had average age of more than 45 years; 7 out of 100 of them were found to be suffering from RA. The average body mass index of the population was in the overweight range. Additionally, the average number of pregnancies was more than 5, and the number of live children was over 4. The average age of RA onset was 38.2 years. The average age at first pregnancy was 20.37 years within our population.
This study showed that the number of pregnancies, the age of the first pregnancy, the duration of breastfeeding, the number of children, the number of abortions, and stillbirths, had no statistically significant correlation with RA. However, a review article by Alpízar and colleagues highlighted controversies in different studies regarding whether these factors are associated with RA. Some studies suggested a protective effect, while others considered them as risk factors for developing RA(6).
Our study supported previous research findings regarding the relationship between years of education and rheumatoid arthritis (RA). Years of education had an inverse relationship with RA. Previous studies have shown an association between higher levels of education and a decreased risk of RA; However, the findings have been inconsistent, and the reasons behind this association remain unclear (12).
In our analysis, we found that marital status did not show a significant correlation with RA. It seems to be more of a prognostic factor rather than a causal or protective factor (13). Many studies have shown that married individuals tend to have fewer health problems and lower mortality rates compared to those who are not married, including divorced, widowed, separated, or never married individuals (13). Being in a well-adjusted or nondistressed marriage seems to be associated with less pain and better functioning for individuals with RA(14).
In our study, we did not find a link between waist circumference and body mass index (BMI) with rheumatoid arthritis (RA). However, a review and meta-analysis showed that overweight and obese individuals have a higher risk of developing RA compared to those with a normal BMI(15). Specifically, women with a waist circumference greater than 102 cm had 2–3 times the risk of developing RA, while those with a waist circumference greater than 88 cm did not show the same association(16). This association may not have been observed due to the cross-sectional nature of our study. Regarding physical activity, Azeez and colleagues found that exercise led to reductions in weight, waist circumference, and BMI in RA patients (17). Low-intensity leisure-time physical activity (LTPA) was inversely associated with BMI, while moderate/vigorous LTPA showed an inverse relationship with both BMI and waist circumference(18).
The analysis of our population did not show a significant correlation between smoking and rheumatoid arthritis (RA), even though smoking is widely recognized as a significant risk factor for the development of RA(19). The prevalence of smoking was 6% in the RA group and 5% in the non-RA group. Likely due to the low prevalence of smoking in this rural society, no significant relationship between smoking, tobacco use, and rheumatoid arthritis was observed. Cigarette smoking is associated with the risk of chronic inflammatory diseases (CIDs) like RA (20). Heated tobacco products (HTPs) are being promoted as a potentially less harmful alternative to traditional cigarettes, but their impact on CIDs is still under ongoing research(20). In literature, opioids are generally considered for pain management and are not regarded as a risk factor or a protective factor(21).
The age of disease onset was only correlated with marital status and years of education, not any other mentioned variables.
The average age of onset of rheumatoid arthritis in our population was 38.2 years, and the average age at first pregnancy was 20 years. This suggests that the participants in our society completed their reproductive history and family formation before developing rheumatoid arthritis. Therefore, it can be inferred that initiating and completing the reproductive history at a younger age for females does not seem to have an impact on the incidence of rheumatoid arthritis. We believe that the high average age of disease in our society has led to a lack of correlation between women's reproductive factors and RA. This is because the majority of women's history of childbearing occurs before the average age of the disease in our population, especially considering that the age of marriage and pregnancy is lower in our rural population.
The Fasa Persian cohort comprised individuals over 35 years of age. The average age of the participants in our study was over 45 years old, indicating that our study population had nearly completed its reproductive history. This aspect can be considered both a strength and a weakness of our study. The study did not include individuals of childbearing age who had not completed their reproductive history. However, it focused on people who had completed their reproductive history on a cross-sectional basis, thereby strengthening the study. Additionally, the study population was limited to rural areas, so its findings may not apply to urban populations. Despite these weaknesses, our study was conducted on a large population. Furthermore, many reproductive factors in a woman’s life were included and studied in our research.
Given the higher prevalence of rheumatoid arthritis (RA) in women and the increased incidence of RA in middle age (50–60 years)(4), it is recommended that multi-centered longitudinal studies, encompassing both rural and urban populations and conducted as either prospective or retrospective studies, should be undertaken to establish the exact relationship between reproductive factors and rheumatoid arthritis. Additionally, since there are varying results from studies on the impact of female hormones on rheumatoid arthritis(3) and considering the higher prevalence of this disease in women compared to men, it is advisable to assess testosterone levels in men with rheumatoid arthritis. Low testosterone levels may potentially play a greater role than female hormones in the development of the disease.