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However, the effect of co-occurrence of frailty on CHE among single empty-nest elderly with multimorbidity remains unclear. This study aims to explore the effect of co-occurrence of frailty on CHE among single empty-nest elderly with multimorbidity, and whether this effect is moderated by economic status.<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Methods<\/jats:title>\n                <jats:p>A cross-sectional household survey of the older adults in 2019 in Shandong province, China. A total of 606 single empty-nest elderly aged 60\u2009years or older were included in this study. CHE was defined as the out-of-pocket payments for health care that equals or exceeds 40% of the household\u2019 s capacity to pay. Logistic regression models are employed to examine the effect of co-occurrence of frailty on CHE among single empty-nest elderly with multimorbidity. The interaction term is introduced to explore the economic status difference in this effect.<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Results<\/jats:title>\n                <jats:p>The CHE incidence for single empty-nest elderly with multimorbidity alone is 64.2%, and the co-occurrence of frailty results in an increase by almost 1.3 times (84.0%) in CHE incidence among single empty-nest elderly with multimorbidity. The co-occurrence of frailty increases the risk of incurring CHE among the single empty-nest elderly with multimorbidity, with the odds of incurring CHE increased by 3.19 times (OR\u2009=\u20093.19; <jats:italic>P<\/jats:italic>\u2009=\u20090.005). Furthermore, the interaction analysis shows that the effect of co-occurrence of frailty on CHE among single empty-nest elderly with multimorbidity still exist in lower economic status groups (OR\u2009=\u20094.64; <jats:italic>P<\/jats:italic>\u2009=\u20090.027), but not in higher economic status (OR\u2009=\u20092.76; <jats:italic>P<\/jats:italic>\u2009=\u20090.062).<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Conclusions<\/jats:title>\n                <jats:p>This study demonstrates that there is a positive effect of co-occurrence of frailty on the CHE among the single empty-nest elderly with multimorbidity, and this effect varies by economic status. The health policy-makers should reorganize the healthcare system to make it pro-poor, so as to meet the multiple medical demand and reduce the potential economic burden and inequalities of older adults.<\/jats:p>\n              <\/jats:sec>","DOI":"10.1186\/s12939-020-01362-6","type":"journal-article","created":{"date-parts":[[2021,1,7]],"date-time":"2021-01-07T18:04:01Z","timestamp":1610042641000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["Catastrophic health expenditure among single empty-nest elderly with multimorbidity in rural Shandong, China: the effect of co-occurrence of frailty"],"prefix":"10.1186","volume":"20","author":[{"given":"Zhengyue","family":"Jing","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jie","family":"Li","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pei Pei","family":"Fu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yi","family":"Wang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yemin","family":"Yuan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dan","family":"Zhao","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wenting","family":"Hao","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Caiting","family":"Yu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9364-3579","authenticated-orcid":false,"given":"Chengchao","family":"Zhou","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2021,1,7]]},"reference":[{"key":"1362_CR1","doi-asserted-by":"publisher","DOI":"10.18356\/30aa1391-en","volume-title":"World Population Ageing 2019: Highlights","author":"The United Nations","year":"2019","unstructured":"The United Nations. 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