International Classification of Diseases-10th Revision Surrogates of the Modified Frailty Index and 12-Month Referral to the Hospital in an Older Population from Germany.

The International Classification of Diseases-10th revision (ICD-10) surrogates of the modified frailty index (mFI) have been defined in recent research. This study aimed to investigate the prevalence of these ICD-10 surrogates and their association with hospital referral in an older population from Germany. The present sample included adults aged ≥65 years followed in German general practices between 2010 and 2021. The index date was the most recent visit date. There were 11 ICD-10 surrogates of the mFI, including a total of 52 diagnoses. These surrogates were assessed in the 12 months prior to the index date. Referral to the hospital was analyzed in the 12 months following the index date. Covariates included age and sex. There were 1,406,038 patients included in the study (mean (standard deviation) age 77.0 (7.9) years; 56.2% women). The prevalence of the ICD-10 surrogates of the mFI ranged from 3.3% for a "history of transient ischemic attack or stroke without neurological deficit" to 68.1% for a "history of hypertension requiring medication". In addition, 24%, 37%, and 23% of participants had 1, 2-3, and >3 ICD-10 surrogates of the mFI, respectively. There was a positive and significant relationship between the number of ICD-10 surrogates and 12-month incident hospital referral (reference: 0 surrogate; 1 surrogate: HR = 1.37, 95% CI = 1.31-1.42; 2-3 surrogates: HR = 2.00, 95% CI = 1.93-2.08; >3 surrogates: HR = 3.32, 95% CI = 3.19-3.44). ICD-10 surrogates of the mFI were relatively frequent and were significantly associated with 12-month incident hospital referral in this sample of older adults from general practices in Germany.