Neuroanatomical and prognostic associations of depression in Parkinson's disease

BACKGROUND

Depression is reported as a risk factor, prodromal feature and late consequence of Parkinson's disease (PD). We aimed to evaluate the timing, neuroanatomy and prognostic implications of depression in PD.

METHODS

We used data from 434 023 participants from UK Biobank with 14.1 years of follow-up. Multivariable regression models established associations of depression with incident PD and regional brain volumes. Cox proportional hazards models assessed prognostic associations of depression in PD with incident dementia and all-cause mortality.

RESULTS

Of 2632 individuals with incident PD, 539 (20.5%) were diagnosed with depression at some point. Depression was associated with an increased risk of subsequent PD (risk ratio 1.53, 95% CI 1.37 to 1.72). Among incident PD cases, depression prevalence rose progressively from 10 years pre-PD diagnosis (OR 2.10, 95% CI 1.57 to 2.83) to 10 years postdiagnosis (OR 3.51, 95% CI 1.33 to 9.22). Depression severity in PD was associated with reduced grey matter volume in structures including the thalamus and amygdala. Depression prior to PD diagnosis increased risk of dementia (HR 1.47, 95% CI 1.05 to 2.07) and mortality (HR 1.30, 95% CI 1.07 to 1.58).

CONCLUSIONS

This large-scale prospective study demonstrated that depression prevalence increases from 10 years before PD diagnosis and is a marker of cortical and subcortical volume loss. Depression before PD diagnosis signals a worse prognosis in terms of dementia and mortality. This has clinical implications in stratifying people with poorer cognitive and prognostic trajectory in PD.

Gene-Environment Interactions for Parkinson's Disease

OBJECTIVE

Parkinson's disease (PD) is a neurodegenerative disorder with complex etiology. Multiple genetic and environmental factors have been associated with PD, but most PD risk remains unexplained. The aim of this study was to test for statistical interactions between PD-related genetic and environmental exposures in the 23andMe, Inc. research dataset.

METHODS

Using a validated PD polygenic risk score and common PD-associated variants in the GBA gene, we explored interactions between genetic susceptibility factors and 7 lifestyle and environmental factors: body mass index (BMI), type 2 diabetes (T2D), tobacco use, caffeine consumption, pesticide exposure, head injury, and physical activity (PA).

RESULTS

We observed that T2D, as well as higher BMI, caffeine consumption, and tobacco use, were associated with lower odds of PD, whereas head injury, pesticide exposure, GBA carrier status, and PD polygenic risk score were associated with higher odds. No significant association was observed between PA and PD. In interaction analyses, we found statistical evidence for an interaction between polygenic risk of PD and the following environmental/lifestyle factors: T2D (p = 6.502 × 10-8), PA (p = 8.745 × 10-5), BMI (p = 4.314 × 10-4), and tobacco use (p = 2.236 × 10-3). Although BMI and tobacco use were associated with lower odds of PD regardless of the extent of individual genetic liability, the direction of the relationship between odds of PD and T2D, as well as PD and PA, varied depending on polygenic risk score.

INTERPRETATION

We provide preliminary evidence that associations between some environmental and lifestyle factors and PD may be modified by genotype. ANN NEUROL 2024;95:677-687.

Towards a global view of multiple sclerosis genetics

Multiple sclerosis (MS) is a neuroimmunological disorder of the CNS with a strong heritable component. The genetic architecture of MS susceptibility is well understood in populations of European ancestry. However, the extent to which this architecture explains MS susceptibility in populations of non-European ancestry remains unclear. In this Perspective article, we outline the scientific arguments for studying MS genetics in ancestrally diverse populations. We argue that this approach is likely to yield insights that could benefit individuals with MS from all ancestral groups. We explore the logistical and theoretical challenges that have held back this field to date and conclude that, despite these challenges, inclusion of participants of non-European ancestry in MS genetics studies will ultimately be of value to all patients with MS worldwide.

134 Predictors of serum vitamin D level in multiple sclerosis

Background

Low serum 25(OH)D3 (vD) in early disease may be associated with worse prognosis in multiple sclerosis (MS). Determinants of serum vD concentration are established in healthy individuals, but poorly studied in people with MS (pwMS). Unpicking the determinants of vD concentration in pwMS may have important preventative and therapeutic implications.

Methods

We recruited a study cohort of pwMS from the UK MS Register (n=315) and matched controls (n=232). We measured serum 25(OH)D3 and genotyped six vD-associated SNPs. We developed a weighted genetic risk score (GRS) using these SNPs and validated it in 373,357 UK Biobank participants. We then assessed predictors of vD levels in our cohort and constructed multivariable models to assess the influence of GRS.

Results

The GRS was well-validated, being strongly associated with vD status in the Biobank cohort (p<2x10-16). In our study cohort, taking vD supplementation, having MS, lower BMI, increased age and supplementation dose were associated with higher vD levels (false discovery rate, FDR<5%). In multivariable models adjusting for these confounders, GRS was strongly associated with vD level in non-supplementers (p=0.004), but not in supplementers (p=0.47).

Conclusions

Our findings suggest vD supplementation is the most important determinant of vD level in pwMS, and genetic determinants may play a relatively minor role.

091 Evaluation of remote assessments for multiple sclerosis in a real-world setting

Background

There is an urgent need for reliable methods to remotely monitor Multiple Sclerosis (MS). Existing assessments, such as Timed 25-Foot Walk (T25FW) and 9-Hole Peg Test (9HPT), are traditionally carried out in person by physicians. The use of self-administered, remote versions of these assessments could improve monitoring and hence care for people with MS (pwMS). This study evaluated the use of remote T25FW (rT25FW) and 9HPT (r9HPT) assessments.

Methods pwMS were given comprehensive instructions and equipment for completing rT25FW/r9HPT. We assessed relationships between EDSS scores (through a previously-validated webEDSS) and contem- poraneous rT25FW/r9HPT using Spearman’s rank-order correlation, to evaluate consistency with previous in-person studies.

Results

Seventy-one pwMS completed the webEDSS and r9HPT, and 108 completed the webEDSS and rT25FW. There was a mild-moderate positive correlation between webEDSS and rT25FW (rho=0.40, p<0.0001, 95%CI=0.23–0.55), a finding consistent with previous in-person studies. There was a non-significant weak correlation between webEDSS and r9HPT. Distributions of rT25FW/r9HPT times were positively skewed. 100% of r9HPT times and 93.5% of rT25FW times were within specified limits used in clinical trials.

Conclusion

These findings provide pilot evidence to indicate remote monitoring of MS is feasible. These assessments should be further developed to aid remote follow-up of pwMS.

ashvin.kuri99@gmail.com

Parkinson’s disease determinants, prediction and gene-environment interac- tions: a UK Biobank study

Introduction

Early identification of individuals at high-risk of Parkinson’s disease (PD) may allow for the use of disease modifying treatments. We aimed to define those at risk of incident PD through environmental and genetic risk factors, comorbidities and prodromal symptoms of PD.

Methods

We identified incident cases of PD (n=1276) in the UK Biobank and unmatched controls without a PD diagnosis (n=500,406). Odds ratios for a range of determinants were calculated. A non-genetic model and polygenic risk score (PRS) were constructed. Basic gene-environment interactions were explored.

Results

Strong evidence of association (FDR < 0.05) was found between PD and family history of PD or dementia, not smoking, low alcohol consumption, depression, daytime somnolence, epilepsy and earlier menarche. Individuals in the top PRS decile had an increased risk of PD compared to those in the lowest decline and high scores were associated with an earlier age of diagnosis. There was evidence for a strong interaction between diabetes and PRS.

Discussion

We report the novel finding of a strong association between earlier menarche and increased PD. Analysis of gene-environment interactions found strong evidence that the effect of diabetes is modified by genetic risk. Replication and understanding the mechanism of this observation is an important next step.

d.belete@nhs.net

Predicting Multiple Sclerosis: Challenges and Opportunities

Determining effective means of preventing Multiple Sclerosis (MS) relies on testing preventive strategies in trial populations. However, because of the low incidence of MS, demonstrating that a preventive measure has benefit requires either very large trial populations or an enriched population with a higher disease incidence. Risk scores which incorporate genetic and environmental data could be used, in principle, to identify high-risk individuals for enrolment in preventive trials. Here we discuss the concepts of developing predictive scores for identifying individuals at high risk of MS. We discuss the empirical efforts to do so using real cohorts, and some of the challenges-both theoretical and practical-limiting this work. We argue that such scores could offer a means of risk stratification for preventive trial design, but are unlikely to ever constitute a clinically-helpful approach to predicting MS for an individual.

Evaluation of remote assessments for multiple sclerosis in an in-home setting

BACKGROUND

There is an urgent clinical need for reliable remote monitoring methods in Multiple Sclerosis (MS). We evaluated the use of remotely patient-recorded timed 25-foot walk (rT25FW) and nine-hole peg test (r9HPT).

METHODS

Seventy-one people with MS completed a previously-validated online EDSS (webEDSS) and r9HPT, and 108 completed the webEDSS and rT25FW.

RESULTS

There was a mild-moderate positive correlation between webEDSS and rT25FW, and no significant correlation between webEDSS and r9HPT. Distributions of rT25FW and r9HPT times were positively skewed.

CONCLUSIONS

Our results provide pilot evidence that remote monitoring of MS is potentially valid but requires refinement before wide-scale implementation. With a median EDSS of 4.5 and EDSS range of 0 - 8.0, at least some patients with ambulatory difficulty are able to complete the assessments.

Gene-Environment Interactions in Multiple Sclerosis: A UK Biobank Study

Objective

We sought to determine whether genetic risk modifies the effect of environmental risk factors for multiple sclerosis (MS). To test this hypothesis, we tested for statistical interaction between polygenic risk scores (PRS) capturing genetic susceptibility to MS and environmental risk factors for MS in UK Biobank.

Methods

People with MS were identified within UK Biobank using ICD-10–coded MS or self-report. Associations between environmental risk factors and MS risk were quantified with a case-control design using multivariable logistic regression. PRS were derived using the clumping-and-thresholding approach with external weights from the largest genome-wide association study of MS. Separate scores were created including major histocompatibility complex (MHC) (PRS_MHC) and excluding (PRS_non-MHC) the MHC locus. The best-performing PRS were identified in 30% of the cohort and validated in the remaining 70%. Interaction between environmental and genetic risk factors was quantified using the attributable proportion due to interaction (AP) and multiplicative interaction.

Results

Data were available for 2,250 people with MS and 486,000 controls. Childhood obesity, earlier age at menarche, and smoking were associated with MS. The optimal PRS were strongly associated with MS in the validation cohort (PRS_MHC: Nagelkerke's pseudo-R² 0.033, p = 3.92 × 10⁻¹¹¹; PRS_non-MHC: Nagelkerke's pseudo-R² 0.013, p = 3.73 × 10⁻⁴³). There was strong evidence of interaction between polygenic risk for MS and childhood obesity (PRS_MHC: AP = 0.17, 95% CI 0.06–0.25, p = 0.004; PRS_non-MHC: AP = 0.17, 95% CI 0.06–0.27, p = 0.006).

Conclusions

This study provides novel evidence for an interaction between childhood obesity and a high burden of autosomal genetic risk. These findings may have significant implications for our understanding of MS biology and inform targeted prevention strategies.

Lower Lymphocyte Count is Associated With Increased Risk of Parkinson's Disease

Objectives:

Patients with established Parkinson’s disease (PD) display differences in peripheral blood markers of immune function, including leukocyte differential counts, compared with controls. These differences may be useful biomarkers to predict PD and may shed light on pathogenesis. We sought to identify whether peripheral immune dysregulation was associated with increased risk of subsequent PD diagnosis.

Methods:

We examined the relationship between incident PD, baseline differential leukocyte count and other blood markers of acute inflammation in UK Biobank (UKB), a longitudinal cohort with ~500,000 participants. We used a range of sensitivity analyses and Mendelian randomization (MR) to further explore the nature of associations.

Results:

After excluding individuals with comorbidities which could influence biomarkers of inflammation, 465 incident PD cases and 312,125 controls remained. Lower lymphocyte count was associated with increased risk of subsequent PD diagnosis (per 1-SD decrease in lymphocyte count odds ratio [OR] = 1.18, 95% confidence interval [CI] = 1.07–1.32, p_adjusted = 0.01). There was some evidence that reductions in eosinophil counts, monocyte counts and C-reactive protein (CRP) were associated with increased PD risk, and that higher neutrophil count was also associated. Only the association between lower lymphocyte count and increased PD risk remained robust to sensitivity analyses. MR suggested that the effect of lower lymphocyte count on PD risk may be causal (per 1-SD decrease in lymphocyte count; OR_MR = 1.09, 95% CI = 1.01–1.18, p = 0.02).

Interpretation:

We provide converging evidence from observational analyses in UKB and MR that lower lymphocyte count is associated with an increased risk of subsequent PD.

Remote testing of vitamin D levels across the UK MS population-A case control study

Objective

The association between vitamin D deficiency and multiple sclerosis (MS) is well described. We set out to use remote sampling to ascertain vitamin D status and vitamin D supplementation in a cross-sectional study of people with MS across the UK.

Methods

People with MS and matched controls were recruited from across the UK. 1768 people with MS enrolled in the study; remote sampling kits were distributed to a subgroup. Dried blood spots (DBS) were used to assess serum 25(OH)D in people with MS and controls.

Results

1768 MS participants completed the questionnaire; 388 MS participants and 309 controls provided biological samples. Serum 25(OH)D was higher in MS than controls (median 71nmol/L vs 49nmol/L). A higher proportion of MS participants than controls supplemented (72% vs 26%, p<0.001); people with MS supplemented at higher vD doses than controls (median 1600 vs 600 IU/day, p<0.001). People with MS who did not supplement had lower serum 25(OH)D levels than non-supplementing controls (median 38 nmol/L vs 44 nmol/L). Participants engaged well with remote sampling.

Conclusions

The UK MS population have higher serum 25(OH)D than controls, mainly as a result of vitamin D supplementation. Remote sampling is a feasible way of carrying out large studies.

Parkinson's disease determinants, prediction and gene-environment interactions in the UK Biobank

OBJECTIVE

To systematically investigate the association of environmental risk factors and prodromal features with incident Parkinson's disease (PD) diagnosis and the interaction of genetic risk with these factors. To evaluate whether existing risk prediction algorithms are improved by the inclusion of genetic risk scores.

METHODS

We identified individuals with an incident diagnosis of PD (n=1276) and controls (n=500 406) in UK Biobank. We determined the association of risk factors with incident PD using adjusted logistic regression models. We constructed polygenic risk scores (PRSs) using external weights and selected the best PRS from a subset of the cohort (30%). The PRS was used in a separate testing set (70%) to examine gene-environment interactions and compare predictive models for PD.

RESULTS

Strong evidence of association (false discovery rate <0.05) was found between PD and a positive family history of PD, a positive family history of dementia, non-smoking, low alcohol consumption, depression, daytime somnolence, epilepsy and earlier menarche. Individuals with the highest 10% of PRSs had increased risk of PD (OR 3.37, 95% CI 2.41 to 4.70) compared with the lowest risk decile. A higher PRS was associated with earlier age at PD diagnosis and inclusion of the PRS in the PREDICT-PD algorithm led to a modest improvement in model performance. We found evidence of an interaction between the PRS and diabetes.

INTERPRETATION

Here, we used UK Biobank data to reproduce several well-known associations with PD, to demonstrate the validity of a PRS and to demonstrate a novel gene-environment interaction, whereby the effect of diabetes on PD risk appears to depend on background genetic risk for PD.

Epidemiology of Epstein-Barr virus infection and infectious mononucleosis in the United Kingdom

BACKGROUND

Epstein-Barr Virus (EBV) is a ubiquitous gamma-herpesvirus with which ~ 95% of the healthy population is infected. EBV infection has been implicated in a range of haematological malignancies and autoimmune diseases. Delayed primary EBV infection increases the risk of subsequent complications. Contemporaneous seroepidemiological data is needed to establish best approaches for successful vaccination strategies in the future.

METHODS

We conducted a sero-epidemiological survey using serum samples from 2325 individuals between 0 and 25 years old to assess prevalence of detectable anti-EBV antibodies. Second, we conducted a retrospective review of Hospital Episode Statistics to examine changes in Infectious Mononucleosis (IM) incidence over time. We then conducted a large case-control study of 6306 prevalent IM cases and 1,009,971 unmatched controls extracted from an East London GP database to determine exposures associated with IM.

RESULTS

1982/2325 individuals (85.3%) were EBV seropositive. EBV seropositivity increased more rapidly in females than males during adolescence (age 10-15). Between 2002 and 2013, the incidence of IM (derived from hospital admissions data) increased. Exposures associated with an increased risk of IM were lower BMI, White ethnicity, and not smoking.

CONCLUSIONS

We report that overall EBV seroprevalence in the UK appears to have increased, and that a sharp increase in EBV seropositivity is seen in adolescent females, but not males. The incidence of IM requiring hospitalisation is increasing. Exposures associated with prevalent IM in a diverse population include white ethnicity, lower BMI, and never-smoking, and these exposures interact with each other. Lastly, we provide pilot evidence suggesting that antibody responses to vaccine and commonly encountered pathogens do not appear to be diminished among EBV-seronegative individuals. Our findings could help to inform vaccine study designs in efforts to prevent IM and late complications of EBV infection, such as Multiple Sclerosis.

Cladribine: mechanisms and mysteries in multiple sclerosis

OBJECTIVES

The aims of this manuscript were to review the evidence for the efficacy and safety of cladribine in multiple sclerosis (MS) and to review the molecular and cellular mechanisms by which cladribine acts as a disease-modifying therapy in MS.

METHODS

This is a narrative review of the available clinical and preclinical data on the use of cladribine in MS.

RESULTS

Clinical trial data argue strongly that cladribine is a safe and effective therapy for relapsing MS and that it may also be beneficial in progressive MS. The pharmacology of cladribine explains how it is selectively toxic towards lymphocytes. Immunophenotyping studies show that cladribine depletes lymphocyte populations in vivo with a predilection for B cells. In vitro studies demonstrate that cladribine also exerts immunomodulatory influences over innate and adaptive immunity.

CONCLUSIONS

Cladribine is a safe and effective form of induction therapy for relapsing MS. Its mechanism of benefit is not fully understood but the most striking action is selective, long-lasting, depletion of B lymphocytes with a particular predilection for memory B cells. The in vivo relevance of its other immunomodulatory actions is unknown. The hypothesis that cladribine's action of benefit is to deplete memory B cells is important: if correct, it implies that selective targeting of this cell population and sparing of other lymphocytes could modify disease activity without predisposing to immunosuppression-related complications.

A dangerous method? The use of induced pluripotent stem cells as a model for schizophrenia

Schizophrenia is a devastating and prevalent psychiatric illness. Progress in understanding the basic pathophysiological processes underlying this disorder has been hindered by the lack of appropriate models. With the advent of induced pluripotent stem cell (iPSC) technology, it is now possible to generate live neurons in vitro from somatic tissue of schizophrenia patients. Despite its several limitations, this revolutionary technology has already helped to advance our understanding of schizophrenia. The phenotypic insights garnered with iPSC models of schizophrenia include transcriptional dysregulation, oxidative stress synaptic dysregulation, and neurodevelopmental abnormalities. Potential pitfalls of this work include the possibility of introducing random genetic mutations during the reprogramming process, the inadequacy of using neurons from other patients as controls, the inability to capture the complex environmental contribution to schizophrenia pathogenesis, the difficulty in modelling neurodevelopment, and the difficulty in modelling the interaction of multiple neuronal and non-neuronal cell types. However, with the increasing sophistication of available reprogramming techniques, co-culture technology, and gene correction strategies, iPSC-derived neurons will continue to elucidate how neuronal function is disrupted in schizophrenia.

Is there a moral obligation to select healthy children?

Reproductive decision-making in the post-genetic age is a minefield of complex ethical problems. One such problem centres on whether there is an obligation on reproducers to choose the best possible child. This paper focusses on a simplified scenario: there are two embryos to choose from, one of which will develop a condition that diminishes quality of life but would still have 'a life worth living', the other of which is normal. Is there an obligation to choose the healthier child? If so, what is the nature and scope of this obligation? The answer to these questions relies on a satisfactory answer to the non-identity problem (NIP). This paper explores several solutions to the NIP and argues for a solution grounded in the concept of harm. Various accounts of harm are discussed and synthesised to provide a new 'comparative bad state view' of harm. This account is used to justify the obligation to choose the healthier child. How far should this obligation go? This paper rejects the conservative position of 'procreative autonomy' - which holds that such obligations have no place in reproductive decisions - and the radical position of 'procreative beneficence' - which holds that there is an even stronger obligation to make the best possible child. The obligation to choose the healthier child may be over-ridden by countervailing reasons; the moral calculus in any individual case will be largely dependent on the expected quality of life of the child.

Stemming the hype: what can we learn from iPSC models of Parkinson's disease and how can we learn it?

Parkinson's disease (PD) is a prevalent and debilitating neurodegenerative disorder for which there are no available cures. PD pathogenesis is poorly understood because appropriate animal and in vitro models are lacking. The development of induced Pluripotent Stem Cells (iPSCs) has allowed researchers to generate disease-specific dopaminergic neurons in vitro by reprogramming skin cells from patients with the disease. It is hoped that this unprecedented access to PD patients' neurons will yield mechanistic insights into PD pathogenesis, a platform for drug screening, and a means of early diagnosis. In this article I critically evaluate the current usage of iPSCs in PD research. I first outline the iPSC paradigm and emphasise the benefits of this approach for modelling PD. I then ask what we can learn from the iPSC-based studies done to date. I argue that these studies have not been particularly informative when considered as an isolated body of evidence. I suggest that the limitations of this technology can be overcome, and I conclude that iPSCs have the potential to be an extremely useful tool in PD research. However, they will never be a panacea and should continue to be used in concert with other in vitro and animal models.

Evaluation of two mycotoxin mitigation strategies in grow-finish swine diets containing corn dried distillers grains with solubles naturally contaminated with deoxynivalenol

A total of 1,040 growing pigs (initially, 22.9 ± 4.3 kg) were used in a 115-d study to evaluate the effects of 2 mycotoxin mitigation strategies, a preservative blend (PB) and a yeast product (YP), on the growth performance of swine fed diets containing corn dried distillers grains with solubles naturally contaminated with deoxynivalenol (DON). The PB consists of preservatives, antioxidants, AA, and direct-fed microbials and is included in diets to help pigs cope with the toxic effects of ingested mycotoxins. The YP works as an adsorbent to bind and prevent the absorption of mycotoxins in the gastrointestinal tract. Pigs were allotted to pens by initial BW and sex; pens were then assigned to treatments in a randomized block design with initial BW and sex serving as the blocking factors. Pens were randomly allotted to 1 of 4 dietary treatments consisting of a positive control (PC) containing <1 mg kg(-1) DON, a negative control (NC) formulated to contain 4 mg kg(-1) DON, NC with PB, and NC with YP. From d 0 to 42 and 42 to 84, no effect of diets containing PB or YP were observed for any of the growth criteria evaluated. From d 84 to 115, pigs fed PC or diets containing PB had improved (P < 0.05) ADG compared to pigs fed NC or diets containing YP, whereas pigs fed YP had improved (P < 0.05) ADG compared to those fed NC. Pigs fed diets containing PB or YP had improved (P < 0.05) ADFI and G:F compared to pigs fed NC. Overall (d 0 to 115), pigs fed diets containing PB had improved (P < 0.05) ADG, ADFI, and G:F compared to pigs fed NC. These results indicate that PB may be a suitable mycotoxin mitigation strategy in growing swine fed diets naturally contaminated with DON.

Effects of drying methods on nitrogen and energy concentrations in pig feces and urine, and poultry excreta

Accurate estimations of nutrient digestion and retention are critical in nutrient balance and feed evaluation studies because errors that occur are often additive. However, there is no standard universal method for drying feces, urine, or excreta before laboratory analysis. The objective of this study was to evaluate the impact of 4 different drying methods on nutrient concentrations in feces, urine, and excreta. Twelve individually penned growing pigs were fed 1 of 3 diets and 16 pens of 10 growing broilers were fed 1 of 4 diets that differed in NDF and CP. Feces, urine, and excreta that varied in nutrient composition were collected after 7 d of diet adaptation. Samples were dried using 1 of 4 methods: undried (UD), freeze-dried (FD), oven-dried at 55 °C for 48 h (OD55), or oven-dried at 100 °C for 48 h (OD100), after which DM, GE, N, C, and S were determined. In swine feces, drying resulted in a loss of GE (P < 0.10) and S (P < 0.01) by 5 and 58%, respectively, compared with UD feces. There was no difference (P ≥ 0.36) among drying method on DM, GE, N, C, or S concentrations. There were no differences (P ≥ 0.12) in urinary GE due to drying or between drying methods; however, urinary DM was greatest by FD compared with OD (P < 0.05) and greater for OD55 compared with OD100 (P < 0.01). In poultry excreta, GE (P < 0.05), N (P < 0.10), and S (P < 0.01) were reduced by drying by an average of 6, 10, and 66%, respectively. There were no differences (P ≥ 0.50) among drying methods except FD excreta had a greater S concentration than OD (P < 0.10). Regardless of drying method, some GE and N loss appears to be inevitable, but there is no apparent advantage between FD and OD. The apparent greater S losses warrant further investigation.