A new family of quantile regression models applied to nutritional data.

This paper introduces a new family of quantile regression models whose response variable follows a reparameterized Marshall-Olkin distribution indexed by quantile, scale, and asymmetry parameters. The family has arisen by applying the Marshall-Olkin approach to distributions belonging to the location-scale family. Models of higher flexibility and whose structure is similar to generalized linear models were generated by quantile reparameterization. The maximum likelihood (ML) method is presented for the estimation of the model parameters, and simulation studies evaluated the performance of the ML estimators. The advantages of the family are illustrated through an application to a set of nutritional data, whose results indicate it is a good alternative for modeling slightly asymmetric response variables with support on the real line.

Midlife cumulative deficit frailty predicts Alzheimer's disease-related plasma biomarkers in older adults.

BACKGROUND: The study explores whether frailty at midlife predicts mortality and levels of biomarkers associated with Alzheimer's disease and related dementias (ADRD) and neurodegeneration by early old age. We also examine the heritability of frailty across this age period. METHODS: Participants were 1,286 community-dwelling men from the Vietnam Era Twin Study of Aging at average ages 56, 62 and 68, all without ADRD at baseline. The cumulative deficit frailty index (FI) comprised 37 items assessing multiple physiological systems. Plasma biomarkers at age 68 included beta-amyloid (Aß40, Aß42), total tau (t-tau) and neurofilament light chain (NfL). RESULTS: Being frail doubled the risk of all-cause mortality by age 68 (OR = 2.44). Age 56 FI significantly predicted age 68 NfL (P = 0.014), Aß40 (P = 0.001) and Aß42 (P = 0.023), but not t-tau. Age 62 FI predicted all biomarkers at age 68: NfL (P = 0.023), Aß40 (P = 0.002), Aß42 (P = 0.001) and t-tau (P = 0.001). Age 68 FI scores were associated with age 68 levels of NfL (P = 0.027), Aß40 (P < 0.001), Aß42 (P = 0.001) and t-tau (P = 0.003). Genetic influences accounted for 45-48% of the variance in frailty and significantly contributed to its stability across 11 years. CONCLUSIONS: Frailty during one's 50s doubled the risk of mortality by age 68. A mechanism linking frailty and ADRD may be through its associations with biomarkers related to neurodegeneration. Cumulative deficit frailty increases with age but remains moderately heritable across the age range studied. With environmental factors accounting for about half of its variance, early interventions aimed at reducing frailty may help to reduce risk for ADRD.

Iatrogenic cartilage injury associated with the use of stainless-steel cannulas and silicone-guarded cannulas for canine stifle arthroscopy.

OBJECTIVE: To determine the ability to reduce iatrogenic cartilage injury (IACI) during canine stifle arthroscopy by using a silicone arthroscope cannula guard. STUDY DESIGN: Ex vivo canine cadaver experimental study. ANIMALS: Paired canine stifles from 14 cadavers (≥20 kg). METHODS: Stifles (N = 28) were assigned to unguarded traditional or silicone-guarded arthroscopy. Stifle arthroscopy and full joint exploration with meniscal probing was performed by a second-year surgery resident (I.C.) in fourteen canine cadavers, alternating between left and right stifles for guarded vs unguarded arthroscopy. After arthroscopy, stifles were disarticulated, and india ink assay was performed to identify IACI. Total IACI number, lesion length and area, duration of procedure, and procedure difficulty score were recorded for each stifle. RESULTS: Unguarded arthroscopy resulted in more total IACI per joint (unguarded 5.2 ± 3.0, guarded 2.4 ± 1.4; P = .02), larger IACI area (unguarded 5.2 ± 4.2 mm2 , guarded 2.3 ± 1.5 mm2 ; P = .02), and IACI length (unguarded 13.6 ± 6.9 mm, guarded 8.6 ± 5.9 mm; P = .03). No difference was identified in duration of procedure (unguarded 11.8 ± 5.2 minutes, guarded 13.8 ± 4.3 minutes; P = .79) or procedure difficulty score (unguarded 1.7 ± 0.6, guarded 1.6 ± 0.6 P = .73). CONCLUSION: Silicone-guarded arthroscope cannulas decreased IACI number and size during canine cadaveric stifle arthroscopy without increasing duration of procedure or surgical difficulty. CLINICAL SIGNIFICANCE: Silicone-guarded arthroscope cannulas may be safer than traditional cannulas for novice veterinary surgeons performing stifle arthroscopy.