Table 1.

Summary of cross-sectional studies in East Asia.

Ref. No.	Study Country Year Sample Size	Parameters for Evaluated for the Diagnosis of COPD	Parameters for Evaluated for the Diagnosis of Periodontitis	Main Findings
[33]	Zhiqiang Liu et al. China 2012 n = 392	Spirometer FEV1/FVC	PD CEJ BI CAL PLI	Fewer remaining teeth, high PLI scores, and low tooth brushing times are significant correlates of COPD exacerbations, indicating that improving periodontal health and oral hygiene may be a potentially preventive strategy against COPD exacerbations.
[34]	Yan Si et al. China 2012 n = 1019	6MWT, BODE index	CAL PPD BI PI ABL	A strong association between periodontitis and COPD, and PI seemed to be a major periodontal factor for predicting COPD among Chinese adults.
[35]	Xuan Zhou et al. China 2012 n = 306	respiratory function and Respiratory Questionnaire(SGRQ)	missing teeth number, alveolar bone level, PD CAL BI PLI	Poor periodontal health as reflected by missing teeth and plaque index was significantly associated with lower QOL in COPD patients. Promoting dental care and health knowledge helps patients with COPD to prevent and treat COPD.
[36]	Shinsuke Kataoka et al. Japan 2021 n = 1022	FEV1/FVC ratio occlusal force HbA1c FBG	PPD BOP number of teeth	PPD was significantly associated with occlusal force among employees with moderate COPD, and ASCVD, so that future health issues could be accurately predicted from the results of routine dental examinations.
[38]	Jane Harland et al. Japan 2018 n = 1474	Spirometer. 1 s of forced vital capacity	PPD CPI	The association between smoking and COPD was significant for men with periodontitis but was weaker for those without periodontitis, and periodontitis is linked to systemic inflammation in smokers with COPD.
[39]	Takeshi Terashima et al. Japan 2017 n = 136	serum albumin level, Spirometer	BOP PD PCR BMI	Poor periodontal health was associated with hypoalbuminemia, suggesting poor nutritional status and inflammation in COPD.
[40]	Zuomin Wang et al. China 2009 n = 634	Respiratory function questionnaire	PD CAL BI PLI, number of remaining teeth, alveolar bone level	Poor periodontal health, dental care, and oral health knowledge were significantly associated with an increased risk of COPD and promoting dental care improved QOL with COPD patients.