1.Clegg A, Young J, Iliffe S, Rikkert MO, Rockwood K. Frailty in elderly people. The Lancet. 2013;381(9868):752–62.
2.Collard RM, Boter H, Schoevers RA, Oude Voshaar RC. Prevalence of Frailty in Community-Dwelling Older Persons: A Systematic Review. Journal of the American Geriatrics Society. 2012;60(8):1487–92.
3.Kojima G. Frailty as a Predictor of Future Falls Among Community-Dwelling Older People: A Systematic Review and Meta-Analysis. J Am Med Dir Assoc. 2015;16(12):1027–33.
4.Kojima G. Frailty as a predictor of disabilities among community-dwelling older people: a systematic review and meta-analysis. Disabil Rehabil. 2017;39(19):1897–908.
5.At J, Bryce R, Prina M, Acosta D, Ferri CP, Guerra M, et al. Frailty and the prediction of dependence and mortality in low- and middle-income countries: a 10/66 population-based cohort study. BMC Med. 2015;13(1):138.
6.Rockwood K, Mitnitski A. Frailty in Relation to the Accumulation of Deficits. The Journals of Gerontology: Series A. 2007;62(7):722–7.
7.Fried LP, Tangen CM, Walston J, Newman AB, Hirsch C, Gottdiener J, et al. Frailty in older adults: evidence for a phenotype. The journals of gerontology Series A, Biological sciences and medical sciences. 2001;56(3):M146–56.
8.Morley JE, Vellas B, Abellan van Kan G, Anker SD, Bauer JM, Bernabei R, et al. Frailty Consensus: A Call to Action. J Am Med Dir Assoc. 2013;14(6):392–7.
9.Mitnitski AB, Mogilner AJ, Rockwood K. Accumulation of Deficits as a Proxy Measure of Aging. TheScientificWorldJOURNAL. 2001;1.
10.Rockwood K, Mitnitski A. Frailty Defined by Deficit Accumulation and Geriatric Medicine Defined by Frailty. Clinics in geriatric medicine. 2011;27(1):17–26.
11.Cesari M, Gambassi G, Abellan van Kan G, Vellas B. The frailty phenotype and the frailty index: different instruments for different purposes. Age Ageing. 2013;43(1):10–2.
12.Erusalimsky JD, Grillari J, Grune T, Jansen-Duerr P, Lippi G, Sinclair AJ, et al. In Search of ‘Omics’-Based Biomarkers to Predict Risk of Frailty and Its Consequences in Older Individuals: The FRAILOMIC Initiative. Gerontology. 2016;62(2):182–90.
13.Ensrud KE, Ewing SK, Taylor BC, Fink HA, Cawthon PM, Stone KL, et al. Comparison of 2 frailty indexes for prediction of falls, disability, fractures, and death in older women. Archives Of Internal Medicine. 2008;168(4):382–9.
14.Bradlee ML, Mustafa J, Singer MR, Moore LL. High-Protein Foods and Physical Activity Protect Against Age-Related Muscle Loss and Functional Decline. The journals of gerontology Series A, Biological sciences and medical sciences. 2017;73(1):88–94.
15.Buta BJ, Walston JD, Godino JG, Park M, Kalyani RR, Xue Q-L, et al. Frailty assessment instruments: Systematic characterization of the uses and contexts of highly-cited instruments. Ageing Res Rev. 2016;26:53–61.
16.Cable N, Hiyoshi A, Kondo N, Aida J, Sjoqvist H, Kondo K. Identifying Frail-Related Biomarkers among Community-Dwelling Older Adults in Japan: A Research Example from the Japanese Gerontological Evaluation Study. Biomed Res Int. 2018:8.
17.Matchar DB, Chei CL, Yin ZX, Koh V, Chakraborty B, Shi XM, et al. Vitamin D Levels and the Risk of Cognitive Decline in Chinese Elderly People: the Chinese Longitudinal Healthy Longevity Survey. The journals of gerontology Series A, Biological sciences and medical sciences. 2016;71(10):1363–8.
18.Bischoff-Ferrari HA, Dietrich T, Orav EJ, Hu FB, Zhang Y, Karlson EW, et al. Higher 25-hydroxyvitamin D concentrations are associated with better lower-extremity function in both active and inactive persons aged > or = 60 y. The American journal of clinical nutrition. 2004;80(3):752–8.
19.Visser M, Deeg DJ, Lips P. Low vitamin D and high parathyroid hormone levels as determinants of loss of muscle strength and muscle mass (sarcopenia): the Longitudinal Aging Study Amsterdam. The Journal of clinical endocrinology and metabolism. 2003;88(12):5766–72.
20.Murad MH, Elamin KB, Abu Elnour NO, Elamin MB, Alkatib AA, Fatourechi MM, et al. Clinical review: The effect of vitamin D on falls: a systematic review and meta-analysis. The Journal of clinical endocrinology and metabolism. 2011;96(10):2997–3006.
21.Hill TR, Aspray TJ. The role of vitamin D in maintaining bone health in older people. Therapeutic advances in musculoskeletal disease. 2017;9(4):89–95.
22.Kane AE, Sinclair DA. Frailty biomarkers in humans and rodents: Current approaches and future advances. Mechanisms of Ageing and Development. 2019;180:117–28.
23.Anagnostis P, Dimopoulou C, Karras S, Lambrinoudaki I, Goulis DG. Sarcopenia in post-menopausal women: Is there any role for vitamin D? Maturitas. 2015;82(1):56–64.
24.Sanders KM, Scott D, Ebeling PR. Vitamin D Deficiency and its Role in Muscle-Bone Interactions in the Elderly. Curr Osteoporos Rep. 2014;12(1):74–81.
25.Bruyere O, Cavalier E, Buckinx F, Reginster JY. Relevance of vitamin D in the pathogenesis and therapy of frailty. Current opinion in clinical nutrition and metabolic care. 2017;20(1):26–9.
26.Arnson Y, Amital H, Shoenfeld Y. Vitamin D and autoimmunity: New aetiological and therapeutic considerations. Ann Rheum Dis. 2007;66(9):1137–42.
27.Ensrud KE, Ewing SK, Fredman L, Hochberg MC, Cauley JA, Hillier TA, et al. Circulating 25-hydroxyvitamin D levels and frailty status in older women. The Journal of clinical endocrinology and metabolism. 2010;95(12):5266–73.
28.Ensrud KE, Blackwell TL, Cauley JA, Cummings SR, Barrett-Connor E, Dam TT, et al. Circulating 25-hydroxyvitamin D levels and frailty in older men: the osteoporotic fractures in men study. Journal of the American Geriatrics Society. 2011;59(1):101–6.
29.Wong YY, McCaul KA, Yeap BB, Hankey GJ, Flicker L. Low vitamin D status is an independent predictor of increased frailty and all-cause mortality in older men: the Health in Men Study. The Journal of clinical endocrinology and metabolism. 2013;98(9):3821–8.
30.Gutierrez-Robledo LM, Avila-Funes JA, Amieva H, Meillon C, Acosta JL, Navarrete-Reyes AP, et al. Association of low serum 25-hydroxyvitamin D levels with the frailty syndrome in Mexican community-dwelling elderly. The aging male: the official journal of the International Society for the Study of the Aging Male. 2016;19(1):58–63.
31.Buta B, Choudhury PP, Xue QL, Chaves P, Bandeen-Roche K, Shardell M, et al. The Association of Vitamin D Deficiency and Incident Frailty in Older Women: The Role of Cardiometabolic Diseases. Journal of the American Geriatrics Society. 2017;65(3):619–24.
32.Vaes AMM, Brouwer-Brolsma EM, Toussaint N, de Regt M, Tieland M, van Loon LJC, et al. The association between 25-hydroxyvitamin D concentration, physical performance and frailty status in older adults. European journal of nutrition. 2019;58(3):1173–81.
33.van den Berg KS, Arts MHL, Collard RM. Vitamin D deficiency and course of frailty in a depressed older population. 2018:1–7.
34.Spira D, Buchmann N, Konig M, Rosada A, Steinhagen-Thiessen E, Demuth I, et al. Sex-specific differences in the association of vitamin D with low lean mass and frailty: Results from the Berlin Aging Study II. Nutrition (Burbank, Los Angeles County, Calif). 2019;62:1–6.
35.Sousa-Santos AR, Afonso C, Santos A. The association between 25(OH)D levels, frailty status and obesity indices in older adults. 2018;13(8):e0198650.
36.Alvarez-Ríos AI, Guerrero JM, García-García FJ, Rodríguez-Mañas L, Medrano-Campillo P, de la Torre Lanza MA, et al. Associations between frailty and serum N-terminal propeptide of type I procollagen and 25-hydroxyvitamin D in older Spanish women: The Toledo Study for Healthy Aging. Experimental gerontology. 2015;69:79–84.
37.Shardell M, Hicks GE, Miller RR, Kritchevsky S, Andersen D, Bandinelli S, et al. Association of Low Vitamin D Levels With the Frailty Syndrome in Men and Women. The Journals of Gerontology: Series A. 2009;64A(1):69–75.
38.Pabst G, Zimmermann AK, Huth C, Koenig W, Ludwig T, Zierer A, et al. Association of low 25-hydroxyvitamin D levels with the frailty syndrome in an aged population: results from the KORA-age Augsburg study. The journal of nutrition, health & aging. 2015;19(3):258–64.
39.Puts MTE, Visser M, Twisk JWR, Deeg DJH, Lips P. Endocrine and inflammatory markers as predictors of frailty. Clinical Endocrinology. 2005;63(4):403–11.
40.Chang C-I, Chan D-C, Kuo K-N, Hsiung CA, Chen C-Y. Vitamin D insufficiency and frailty syndrome in older adults living in a Northern Taiwan community. Arch Gerontol Geriatr. 2010;50:S17-S21.
41.Zeng Y, Vaupel JW. Chinese Longitudinal Healthy Longevity Survey (CLHLS), Biomarkers Datasets, 2009, 2012, 2014. Inter-university Consortium for Political and Social Research [distributor]; 2019.
42.Zeng Y, Vaupel J, Xiao Z, Liu Y, Zhang C. Chinese Longitudinal Healthy Longevity Survey (CLHLS), 1998–2014. Inter-university Consortium for Political and Social Research [distributor]; 2017.
43.Xiao Q, Wu M, Zeng T. Social support networks in Chinese older adults: health outcomes and health related behaviors: a path analysis. Aging & mental health. 2019:1–9.
44.Zeng Y, Feng Q, Hesketh T, Christensen K, Vaupel JW. Survival, disabilities in activities of daily living, and physical and cognitive functioning among the oldest-old in China: a cohort study. Lancet. 2017;389(10079):1619–29.
45.Lv X, Li W, Ma Y, Chen H, Zeng Y, Yu X, et al. Cognitive decline and mortality among community-dwelling Chinese older people. 2019;17(1):63.
46.Liu Z, Han L, Feng Q, Dupre ME, Gu D, Allore HG, et al. Are China’s oldest-old living longer with less disability? A longitudinal modeling analysis of birth cohorts born 10 years apart. BMC Med. 2019;17(1):23.
47.Lv YB, Gao X, Yin ZX, Chen HS, Luo JS, Brasher MS, et al. Revisiting the association of blood pressure with mortality in oldest old people in China: community based, longitudinal prospective study. Bmj. 2018;361:k2158.
48.Sun D, Sun X, Xu Y, Wu T, Tao L. Superoxide dismutase activity and risk of cognitive decline in older adults: Findings from the Chinese Longitudinal Healthy Longevity Survey. Experimental gerontology. 2019;118:72–7.
49.Yin ZX, Shi XM, Kraus VB, Fitzgerald SM, Qian HZ, Xu JW, et al. High normal plasma triglycerides are associated with preserved cognitive function in Chinese oldest-old. Age Ageing. 2012;41(5):600–6.
50.Dupre ME, Gu D, Warner DF, Yi Z. Frailty and type of death among older adults in China: prospective cohort study. Bmj. 2009;338:b1175.
51.Gaudry M, J. Wills M. Estimating the functional form of travel demand models. Transportation Research. 1978;12:257–89.
52.Cole T. Applied logistic regression. D. W. Hosmer and S. Lemeshow, Wiley, New York, 1989. No. of pages: xiii + 307. Price: £36.00. Statistics in Medicine - STAT MED. 1991;10:1162–3.
53.Turlach B. Spline Smoothing. 2016. p. 1–8.
54.B. Onukogu I. When is Piece-Wise Regression Really Necessary? Biometrical Journal - BIOM J. 1984;26:559–66.
55.Bahrami A, Sadeghnia HR, Tabatabaeizadeh SA, Bahrami-Taghanaki H, Behboodi N, Esmaeili H, et al. Genetic and epigenetic factors influencing vitamin D status. 2018;233(5):4033–43.