Association between breastfeeding and periodontitis in Korean women using Korea National Health and Nutrition Examination Survey (KNHANES): a cross-sectional study

Periodontal disease is one of the most common public health problems, affecting more than 20%-50% of the global population [1]. It is a complex, multi-factorial disease related to dental biofilms [2]. As a chronic inflammatory disease, periodontitis can negatively affect diet, cosmetic, speech, and other aspects of life [3]. Furthermore, there is substantial evidence that periodontitis negatively affects systemic health through various biological mechanisms [4]. A review of periodontitis in women showed that decreased estrogen levels during menopause causes bone loss and leads to recurrence or exacerbation of periodontitis [5]. As women comprise most of the elderly population and the influence of hormones on certain oral diseases has been established, maintaining good oral health throughout a woman's life is an ongoing challenge [6].

It is widely known that breast milk contains various nutrients, and breastfeeding has many health benefits not only for the child but also for the mother [7, 8]. Breastfeeding can reduce maternal risks of breast cancer, ovarian cancer, diabetes, hypertension, cardiovascular disease, and postpartum depression [9‐12]. The World Health Organization recommends exclusive breastfeeding for six months and continued breastfeeding for up to two years [13]. Although breastfeeding rates have increased, 60% of the mothers wish to stop breastfeeding [14]. The health effects of breastfeeding in maternal health have been widely reported, there have been few studies on breastfeeding and maternal oral health.

In South Korea, breastfeeding rates were high in the 1980s and the 1990s, and then began to decline and reached an all-time low in 2000 [15]. A recent study in South Korea showed that the breastfeeding rate increased to 81.5% between 2010 and 2018 [16]. However, compared to other Asian countries, breastfeeding rates in South Korea are lower than that in China (96.1%), Singapore (96%), and India (95.5%) [17].

The are several factors that affect breastfeeding rates [18, 19]. At the personal level, the benefits of breastfeeding are individually subjective factors that influence whether women choose to breastfeed [20]. Although there are many studies on the maternal benefits of breastfeeding in the existing research [20‐23], the oral health benefits of breastfeeding are poorly reported. To the best of our knowledge, only two previous studies have reported the relationship between breastfeeding and periodontitis. Both studies found a negative association [24, 25].

While previous studies provide some possible mechanism for a negative association between breastfeeding and periodontitis, it is without considering potential confounding factors that could influence this relationship, such as diabetes, hypercholesterolemia, and hypertriglyceridemia. In addition, in the breastfeeding period classification of one study, a group less than 18 months was used as a reference and up to 73 months were classified. In another study, breastfeeding period are in years as the continuous variable and the highest period is 15 years. It can be unreasonable classification considering the current situation in which the average birth rates were less than two. By taking these factors into account in our studies, we can better understand the mechanisms underlying the association between breastfeeding and periodontitis.

There is little evidence regarding the precise mechanisms underlying the association between breastfeeding and periodontitis. Thus, the effects of breastfeeding on periodontal health remain largely unknown. Exploring the association between breastfeeding and periodontitis has both scientific and social implications. Therefore, this study aimed to evaluate the effect of breastfeeding behavior on periodontal health in Korean women, thereby providing support for oral health education for lactating women.

A total of 5,806 women that participated in the survey were aged ≥ 30 and gave birth in the past. A total of 219 participants had no periodontal status information, and 5,587 parous women were analyzed. Table 1 shows the descriptive characteristics of the study population, including demographics, individual health practices, and medical status. The mean weighted age of the participants was 60.87 years. The participants without periodontitis had a mean weighted age of 53.03 years. Furthermore, approximately three-fifths of women breastfed for more than 12 months. The least number of women had no breastfeeding experience.

Table 2 shows the multivariate association between breastfeeding and periodontitis. In all statistical models, there was a 60% higher prevalence of periodontitis in women that did not breast feed compared with women that breastfed for 12 months or longer (model 1, aOR, 1.259; 95% CIs, 1.012–1.567; model 4, aOR, 1.597; 95% CIs, 1.199–2.129).

Table 3 shows the results of the model of multiple associations between breastfeeding and periodontitis according to age group. The difference was statistically significant only in the 50–59 age group (P < 0.05). Women aged 50–59 years who had never breastfed were more likely to develop periodontitis than those who had breastfed for ≥ 12 months. (aOR, 1.678; 95% CIs, 1.046–2.691).

This study investigated the association between breastfeeding duration and periodontitis. The results showed that women who breastfed for more than 12 months had a lower risk of periodontitis than non-breastfeeding women, suggests that breastfeeding may have a protective effect on periodontal health. This finding is not consistent with previous researches, which found that a longer duration of breastfeeding could significantly increase periodontitis in postmenopausal Korean women [24]. One possible explanation for this result is that postmenopausal women typically have a higher risk of periodontitis due to hormonal changes and other factors. As described in introduction, the reference group of breastfeeding is different from our study. The previous study could match the elderly who give birth to many children, and this could have bias, which is disadvantageous for periodontal disease research. On the other hand, our study used the reference group that did not breastfeeding as a reference, and other groups are 1–11 months and 12 months or more. It is assumed that the results are naturally different from this previous study and can be reasonable considering low birthrate in Korea. Another previous study revealed that the prevalence rate of periodontal disease was 6.915 times higher when the length of the lactation period was 14 years in Korean female adults [25]. However, the study only analyzed data for one year and did not consider personal healthcare practice, and systematic medical factors. Sample size and whether to consider these variables that directly associated with periodontal health may be the reason for our inconsistent results. Nevertheless, the findings from studies suggest that breastfeeding may have a significant impact on periodontal health, and should be considered as an important factor in promoting oral health and preventing periodontitis in women. It should be noted that the correlation between breastfeeding and periodontitis is multifaceted and can be impacted by several factors., more research is needed to better understand the mechanisms underlying these effects. The mechanism underlying the association between breastfeeding and periodontitis is not yet clear, but there are several hypothesized ways linking the two.

One of the potential mechanisms is related to common risk factor. Periodontitis is a disease characterized as a noncommunicable disease (NCD), is known to be associated with breast cancer, cardiovascular disease (CVD), diabetes, hypertension, Alzheimer's disease, and depression [33]. In that regard, Breastfeeding may reduce the risk of breast cancer, and a significant association between periodontitis and breast cancer has been observed [34‐38]. This suggests that breastfeeding may indirectly reduce the risk of periodontitis by lowering the risk of breast cancer. Additionally, breastfeeding may reduce the risk of cardiovascular diseases and other related risk factors such as type 2 diabetes, hypertension, and Alzheimer's disease, which have been found to be a risk factor for the onset or progression of periodontitis [39‐44]. Another potential mechanism is related to autoimmune diseases, such as rheumatoid arthritis, which may increase the risk of periodontitis [45, 46]. Women who breastfeed for a longer duration may reduce the risk of periodontitis by reducing the risk of autoimmune disease [47, 48]. Finally, depression may also be a factor, as non-breastfeeding women have been found to be more depressed and anxious than breastfeeding women [49‐52]. Depression has been linked to an increased risk of periodontitis [53, 54], and therefore, breastfeeding may indirectly lower the risk of periodontitis by reducing the incidence of depression.

Overall, the study suggests that breastfeeding may have a protective effect against periodontitis, but the mechanisms underlying this association require further investigation. Additionally, the potential links between breastfeeding and breast cancer, cardiovascular disease, autoimmune disease, and depression should be explored in more detail to better understand the relationship between breastfeeding and periodontitis. It is necessary to analyze this part with the integrated data by period of the Korean National Health and Nutrition Examination Survey as a further study.

This study has some limitations. Although it was a National Health Survey, national surveys have several limitations. Periodontitis was assessed using the CPI, which may have underestimated or overestimated outcome [55]. This cross-sectional study does not support a causal relationship between breastfeeding and the prevalence of periodontitis. Additionally, participation in the questionnaire was subject to memory bias and may have contained some inaccuracies. Potential bias could not be ruled out because missing periodontal status data were excluded. Finally, since the study population consisted of Korean women, it is difficult to apply the results to all populations, and a different correlation pattern was observed in other populations.

Despite these limitations, this study has several advantages. First, this is the first study to report that a longer breastfeeding duration may reduce the risk of periodontitis. Second, we used a large national dataset and analyzed a sufficient number of samples. Our findings provide support for maternal oral health education. However, to the best of our knowledge, no studies to date have directly shown that longer breastfeeding duration reduces the risk of periodontitis. Therefore, one important future direction for this study is to thoroughly investigate the precise mechanism underlying the association between breastfeeding and periodontitis.

From the above discussion, it can be concluded that longer breastfeeding duration is significantly associated with a reduced risk of periodontitis in Korean women. This study suggests that breastfeeding may have a protective effect on periodontal health in women. This finding adds another benefit to women who choose to breastfeed. To strengthen the periodontal health management of women, our results can provide literature support for the future oral health education of lactating women.