Depression and anxiety screening improves cardiovascular risk prediction in population-based sample of 4,750 russian individuals

Introduction

Cardiovascular diseases (CVD) are the most serious public health problem, remaining the leading cause of death in the adult population. A great number of CVD risk scales are successfully used in clinics, yet they are tuned to work the best for patients of older age and often are population specific.

Methods

We used the data from a longitudinal epidemiologic study of 4,750 individuals aged 25–64 years from European part of Russia recruited in 2012–2013 to predict the 10-year risk of cardiovascular events in Russian population and evaluate performance for common clinical risk scales. The cohort was divided into two groups: “cases” – individuals with a cardiovascular event registered during the follow up period (2013–2019) as a study group (N=106) and “controls” – individuals with no cardiovascular events registered during follow up as a control group (N=4,644). All individuals with previous history of CVD (ischemic heart disease, stroke or heart attack) prior to 2012 were assigned high risk in all scales.

The case and control groups were split by age: below and above 40 to reflect the properties of cardiovascular risk scales to work best for age over 40.

We assessed CVD risk scores using Framingham 2008 [1], ASCVD 2013, both were calculated with mean parameters values calculated from our cohort and from the original study [2], SCORE 2003, 2017 and 2019 [3] and MOSP - the recalibrated for Russian population scale of the SCORE 2017 [4]

Results

For patients over 40 years old, cardiovascular risk scales showed similar performance, with ASCVD normalized to the original study's mean parameter values returning the best prediction scores. Expectedly, for the younger group of patients, cardiac risk scales do not have notable predictive power.

Further, we thought to identify additional factors discriminating young individuals at higher risk of CVD. We downsampled the control cohort to include only samples with age, weight, height, LDL, total cholesterol and systolic blood pressure matching those in a case cohort (<40 years of age).

186 phenotypic features were tested and 4 out of top 10 (p<0.05) associated features included questions related to depression, anxiety or current stress level from HADS scale, though not significant after multiple hypothesis correction, this suggests that younger individuals with high scores in depression/anxiety screenings might be at higher risk of CVD. Depression/anxiety features were added to cardiovascular risk scales as binary predictor components to improve prediction quality (Table 1).

Conclusions

We identified depression and anxiety screening questionnaires as a valuable predictor for cardiovascular events in the younger population improving the quality of predictions of traditional clinical scales.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Science and Higher Education of the Russian Federation Table 1. ROC analysis

Association between personalized evidence-based anticoagulation therapy and outcomes at 1-year follow-up in patients with atrial fibrillation: an analysis from the Atrial Fibrillation registry

Background

The guideline treatments based on a relatively broad set of enrollment criteria inhibits the personalized evidence-based approach. Personalized evidence-based medicine (EBM) involves the ability to classify individuals into subpopulations that differ in their susceptibility to a particular disease or their response to a specific treatment.

Objective

We report the 1-year follow-up data of the Atrial Fibrillation Registry, focusing on the relationship between personalized EBM and guideline-adherent anticoagulation therapy use and the occurrence of major clinical adverse events.

Methods

2683 patients at high risk for stroke and 1-year follow-up were enrolled in study. The primary endpoint was the percentage of guideline-based and personalized EBM recommendations acted on by clinicians. Secondary endpoints include the following: outcomes for all-cause mortality, thromboembolism (TE), bleeding, and the composite endpoints.

Results

From 2683 patients, 1971 (73.5%) EMR were guideline adherent and only 824 (30.7%) of them were personalized EBM anticoagulation therapy adherent, whilst 712 (26.5%) were non-guideline adherent and 1147 (42.8%) were guideline adherent but non-personalized EBM adherent.

The composite endpoint of cardiovascular death, any TE or bleeding was significantly lower in personalized EBM adherent patients during 1-year follow-up (P=0.02). The endpoint of all cause death and any TE is increased by >20% by guideline adherent but non-personalized EBM adherent treatment [hazard ratio (HR) 1.254 (95% CI 0.931; 1.689)] and >80% non-guideline adherent and non-personalized EBM adherent treatment [HR 1.892 (95% CI 1.359; 2.635)]. For the composite endpoint of cardiovascular death, any TE or bleeding, guideline adherent but non-personalized EBM adherent treatment increased risk by >40% [HR 1.454 (95% CI 1.037; 2.040)], and non-guideline adherent and non-personalized EBM adherent treatment by >110% [HR 2.113 (95% CI 1.453; 3.074)].

Conclusion

Personalized EBM anticoagulation management is associated with significantly better outcomes, including those related to the composite endpoint of cardiovascular death, any TE or bleeding in high-risk patients.

Funding Acknowledgement

Type of funding sources: None.

Clinical and genetic markers of prehypertension in North-Western Russian population

Introduction

Prehypertension is a medical classification for patients with above normal blood pressure (BP) but insufficient for confirming hypertension diagnosis. Condition is often asymptomatic as it gradually develops over the years, yet recent meta-analyses suggest that prehypertension is a significant risk factor for stroke and other cardiovascular diseases.

Methods

We analyzed phenotypic data from 879 (age 25–64) individuals without hypertension from a population based-sampling cohort of St. Petersburg region in the North-West of Russia to identify clinical risk factors associated with prehypertension condition. All patients were divided in two groups – optimal BP (systolic BP <120 mmHg and diastolic BP <80; N=426) and prehypertension (systolic BP in range 120–140 mmHg and diastolic BP in range 80–90 and not on antihypertensive therapy; N=453).

Results

Phenotypic analysis with linear regression was corrected for age, sex, smoking status, BMI and levels of LDL and HDL cholesterol (Figure 1). Interestingly, blood level of insulin was significantly associated with prehypertension status along with insulin resistance index, however, presence of diabetes diagnosis in medical history was not significant. Phenotypes associated with prehypertension suggest that prehypertension is often developing along with hyperinsulinemia.

Finally, we estimated polygenic risk scores (PRS) for hypertension using UK biobank GWAS summary statistics and confirmed that prehypertension is more frequent at earlier age in patients with higher genetic susceptibility (Figure 1, Figure 2).

Conclusions

Hyperinsulinemia and genetic susceptibility to hypertension are strong risk factors for prehypertension.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075-15-2020-901) to Al.K. Figure 1. Clinical markers of prehypertensionFigure 2. Genetic markers of prehypertension

Aortic diameter, pulse wave velocity, central aortic pulse pressure, left ventricular parameters, and diastolic dysfunction in patients with aortic aneurysm

Background

The enlargement of aortic aneurysm can alters pulse wave propagation and reflection, which may influence to left ventricular (LV) afterload changes. The relevance of pulse wave velocity (PWV) and central blood pressure depending on the locus of the aneurysm for LV structure and diastolic function (DF) are not clearly unknown.

Purpose

Assess the relationship between central pulse pressure (CPP), PWV and LV structure and DF in patients with ascending aortic aneurysm (AA) and abdominal aortic aneurysm (AAA).

Methods

121 patients (95 male, 63±12 years) with aortic aneurysms and preserved LV systolic function were enrolled before aortic repair. 51 patients (37 male, 54±13 years) had AA and 70 patients (58 male, 69±7 years) had AAA. CPP and PWV were measured using applanation tonometry. A echocardiographic exam was performed with a Vivid 7 GE (USA). LV mass index (LVMI) and relative wall thickness (RWT) were calculated according to standard formulas. LV filling pressure (E/Em) was estimated by Doppler-derived ratio of mitral inflow velocity (E) to septal (Em) by tissue Doppler. Transmitral flow patterns (E/A ratio of E to late (A) ventricular filling velocities) were measured with the pulsed doppler method.

Results

Concentric LV hypertrophy (LVH) was observed in 51 (42%), eccentric LVH – in 35 (29%) patients. CPP was positively related with LVMI (r=0.362, P=0.001), but PWV was inversely associated with LVMI (r=−0.244, P=0.029). CPP was not associated with RWT (P≥0.5), whereas PWV was positively related (r=0.223, P=0.004). PWV decreased with increasing aortic diameter in AA and AAA (r=−0.360, P=0.029 and r=−0.315, P=0.019, respectively). 12 (23%) patients with AA and 36 (56%) patients with AAA had grade I diastolic dysfunction, 20 (40%) patients with AA and 12 (18%) patients with AAA had grade II diastolic dysfunction (P<0.001). Consequently, the E/A ratio was higher in patients with AA than in patients with AAA (1.21±0.39 vs 0.83±0.33; P=0.007). CPP and PWV was inversely associated with LV DF (E/A: r=−0.352 and −0.238; E/Em: r=−0.292 and −0.279, respectively; both P<0.05). E/A and E/Em increased with the expansion of the maximum aortic diameter at the level of the AA and AAA (E/A: r=0.612 and 0.416; E/Em: r=0.719 and 0.339, respectively; both P<0.005). RWT and LVMI were correlated with the aortic diameter at the level of the AA (r=−0.439, P=0.008 and r=0.286, P=0.05, respectively), but bore no relation with the aortic diameter at the level of the AAA.

Conclusions

In patients with aortic aneurysm CPP and PWV were conjointly but differently related to LV structure. Eccentric LV hypertrophy was accompanied by a significant decrease of PWV. Reduced PWV and decreased CPP exhibited association with more severe LV diastolic dysfunction, possibly due to the apparent effect of increased aortic aneurysm diameter. LV DF was severely reduced in the patients with AA compared by patients with AAA.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Almazov National Medical Research Centre

Determinants of central aortic pressure and pulse pressure amplification changes in patients with aortic aneurysm: the role of aortic diameter and aortic aneurysm location level

Background

The presence of aortic aneurysm can alters pulse wave propagation and reflection, causing changes in central aortic pressure and pulse pressure amplification (PPA) between the aorta and the brachial artery that might be associated with unfavorable hemodynamic effects for the central arteries and the heart. However, the impact of the location of the aneurysm and increase of the aortic diameter on central blood pressure (CBP) is not fully understood.

Objective

To investigate central aortic pressure and PPA regarding to association with arterial stiffness and aortic diameter in patients with ascending aortic aneurysm (AA), descending thoracic and abdominal aortic aneurysm (TAA and AAA).

Methods

122 patients (96 males, 65±11 years) with aortic aneurysm were enrolled before aortic repair. The parameters of the aorta were evaluated by MSCT angiography: 44 patients (30 males, 55±13 years) had AA (the maximum diameter: 59.9±14.2 mm), 13 patients (11 males, 62±11 years) had TAA (the maximum diameter: 62.8±8.0 mm) and 65 patients (54 males, 69±8 years) had AAA (the maximum diameter: 52.3±17.2 mm). Brachial blood pressure (BBP) was measured by OMRON. CBP, augmentation index (AIx), carotid-femoral pulse wave velocity (PWV) were assessed by SphygmoCor. PPA was calculated as a difference between the values of central and brachial pulse pressure (CPP and BPP).

Results

Patients of the three groups did not differ in BPP (AA: 59.2±17.6; TAA 56.8±12.8; AAA: 59.3±11.4 mm Hg; P=0.5). Intergroup comparison revealed a difference in CPP between the three patients groups: CPP was higher in patients with AA and AAA, lower in patients with TAA (AA: 50.3±16.2; TAA 43.8±10.8; AAA: 50.0±11.2 mm Hg; P=0.05). PPA was lower in patients with AA and AAA than in patients with TAA (9.6±6.7 and 9.3±4.2 vs. 13.0±6.5 mm Hg; P=0.05 and P=0.04, respectively). IAx was higher in patients with AA and AAA than in patients with TAA (25.2±8.1 and 27.6±8.2 vs. 17.2±8.2 mm Hg; P=0.008 and P=0.001, respectively). A decrease of PPA across all patients correlated with an increase of IAx (r = - 0.268; P=0.003). CPP decreased with an increase of the aortic diameter for each level of the aneurysm (AA: r = - 0.460, P=0.016; TAA: r = - 0.833, P=0.003; AAA: r = - 0.275, P=0.05). PWV decreased with the expansion of the maximum aortic diameter at the level of the AA, TAA and AAA: (r = - 0.389, P=0.03; r = - 0.827, P=0.02 and r = - 0.350, P=0.01, respectively).

Conclusion

In patients with aortic aneurysm measurements of lower central pulse pressure and reduced PWV indicate an association with increased diameter of the aneurysm. An increase in augmentation index, early return of reflected waves, thus smaller PP amplification and higher CPP were identified in patients with ascending and abdominal aortic aneurysm compared by patients with descending thoracic aortic aneurysm.

Funding Acknowledgement

Type of funding source: None

How do physicians of different specialties assess smoking status in hospital and primary care

Background

Assessment of current smoking status and history of smoking is critically important for risk stratification and initiation of smoking cessation interventions. However, assessment of smoking status it not included in quality of care measurement, thus the information can be frequently missed in patient' records.

Purpose

To investigate how careful smoking status is recorded in hospital and primary care by physicians of different specialties.

Methods

Electronic records from 124097 hospital and primary care adult patients' case histories were analyzed. Records were made by physicians of different specialties in 2018 and reflected all database for one year form big national medical research Centre.

Results

Smoking status was assessed and recorded only in 33504 of all 124097 (27.0%) electronic records, in 4056 of 44007 (9.2%) hospital records and in 29448 of 80090 (36.8%) out-patient episodes (p<0.001). The highest smoking status assessment rate was observed in nephrologists – 284 of 508 (55.9%), oncologists – 82 of 151 (54.3%), gynecologists – 4085 of 8147 (50.1%), cardiologists – 19591 of 40366 (48.5%) and hematologists – 2310 of 4891 (47.2%). The lowest smoking status recording rate was documented in surgery: cardiac surgeons – 243 of 4843 (5.0%), neurosurgeons – 449 of 10161 (4.4%), urologists – 24 of 1686 (1.4%), as well as by ophthalmologists – 5 of 3152 (0.2%). Radiologists, dermatologists, otolaryngologists, genetics and dentists did not include any records of smoking status at all. 72799 (58.7%) of assesses patients were women. Smoking status was more frequently recorded in women – 20780 of 72799 (28.5%) than in men – 12724 of 51298 (24.8%) (p<0.001), and in young patients more often than in elderly patients, thus the reported smoking rate was maximal in the age group of 20–29 years. Among those records, where the status was assessed, smoking was more prevalent among men – 3746 of 12724 (29.4%) compared women – 1901 of 20780 (9.1%).

Conclusions

Smoking status and ex-smoking are indicated in medical records in less than one third of cases, especially low rate was observed in hospital records. No attention to smoking can influence correct risk assessment and lack of advice for smoking cessation. Even cardiologists indicate smoking status in less than 50% of patients' visits. Significant efforts should be made to emphasize the importance of risk factor assessment with a special attention to smoking as a potentially modifiable risk factor in order to decrease mortality and morbidity in Russia.

Funding Acknowledgement

Type of funding source: None

P1554Is self-reported sleep-disordered breathing associated with increased cardiovascular risk?

Background

Sleep-disordered breathing (SDB) is associated with the increased cardiovascular (CV) morbidity and mortality. However, sleep apnea is not considered in the standard scales used for the risk stratification.

Purpose

We evaluated the association between self-reported SDB and SCORE risk (the 10-year risk of fatal CV events according to the systemic coronary risk evaluation) in the population-based sample from St Petersburg.

Methods

We selected 1555 subjects without previously known CV events (550 males, 35%; mean age 46.7±11.6 years old) out of 1600 participants of the population-based sample (from the epidemiological study ESSE-RF, St Petersburg). All subjects were interviewed (questions about lifestyle, medical history, complaints) using standard questionnaire. We assessed self-reported snore (“Do you snore?”) and sleep apnea (“Do you have sleep apneas?”). Affirmative response was considered diagnostic. Daytime sleepiness was assessed based on the answers >3 times/week to the question “How often have you been unable to refrain sleeping when required?”. The 10-year risk of fatal CV events was assessed by the SCORE high-risk charts calculator. For statistical analysis we used parametric statistics, frequency and contingency analyses (Chi-square), multiple logistic regression analysis (stepwise inclusion; the parameters not evaluated in the SCORE scale were considered, i.e. body mass index, glucose level, triglyceride, HDL-cholesterol, creatinine, C-reactive protein, self-reported insomnia).

Results

Based on the SCORE assessment the participants were divided as following: low risk (<1%) was the most predominant category (n=864, 55.6%); moderate risk (≥1% and <5%) was found in 468 (30.1%), high risk (5–10%) – in 184 (11.8%), and very high risk – in 39 (2.5%) subjects. In total, 740 (47.6%) subjects had snoring, while only 77 (5%) subjects reported sleep apneas. Neither self-reported snoring nor sleep apnea were associated with daytime sleepiness (p>0.05). High-to-very-high SCORE risk was found more often in subjects with self-reported snoring compared to non-snorers: 21.2% vs. 8.1%, respectively (Chi-square=54.3, p<0.001). At the same time no association was found between self-reported sleep apneas and cardiovascular risk. Logistic regression demonstrated an association between SCORE risk and self-reported snoring (OR=3.06 95% CI 2.25–4.16, p<0.001). Multiple regression analysis confirmed the impact of snoring in the increased SCORE risk (OR=2.16 95% CI 1.55–3.02, p<0.001) after adjustment for the other factors.

Conclusions

Our study demonstrated that in Russian population-based sample self-reported snoring (unlike self-reported sleep apnea) is associated with the increased 10-year risk of fatal CV events. The lack of association between SCORE risk and sleep apnea might be related to the subjective assessment based on the questionnaire.

Acknowledgement/Funding

The study was supported by the Grant of the President of Russian Federation for the Leading Scientific Schools of Russia (agreement No. 075-02-2018-57,

Lifetime Prevalence of Transient Loss of Consciousness in an Urban Russian Population

BACKGROUND

Most international studies on epidemiology of transient loss of consciousness (TLC) were performed many years ago. There are no data about the lifetime prevalence of TLC in Russia.

OBJECTIVE

To identify the lifetime prevalence and presumed mechanisms of TLC in an urban Russian population.

METHODS

1796 individuals (540 males [30.1%] and 1256 females [69.9%]) aged 20 to 69 years (mean age 45.8 ± 11.9 years) were randomly selected and interviewed within the framework of multicentre randomised observational trial.

RESULTS

The overall prevalence of TLC in the studied population was 23.3% (418/1796), with the highest proportion (28%) seen in 40-49 year age group. TLC was significantly more common in women than in men (27.5% vs 13.5%). The mean age of patients at the time of the first event was 16 (11; 23) years, with 333 (85%) individuals experiencing the first episode of TLC under 30 years. The average time after the first episode of TLC was 27 (12; 47) years. The following mechanisms of TLC were determined using the questionnaire: neurally-mediated syncope (56.5%), arrhythmogenic onset of syncope (6.0%), nonsyncopal origin of TLC (1.4%), single episode during lifetime (2.1%). Reasons for TLC remained unidentified in 34% cases. 27 persons (6.5%) reported a family history of sudden death, mainly patients with presumably arrhythmogenic origin (24%).

CONCLUSION

Our findings suggest that the overall prevalence of TLC in individuals aged 20-69 years is high. The most common cause of TLC is neurally-mediated syncope. These data about the epidemiology can help to develop cost-effective management approaches to TLC.

Understanding rape survivors' preparations for court

This article concerns rape survivors' preparation for courtroom appearances. It is an inductive analysis of face-to-face interviews and courtroom observation. The study builds on research about resistance to rape, reporting, the prosecution of rape, and anthropological studies of legal consciousness. It begins with descriptions of survivors' preparation activities: appearance work, rehearsal, emotion work, team building, role research, and case enhancement. It then explores how survivors' legal experience and knowledge of the legal system, awareness of dominant cultural understandings of rape, personal sense of efficacy, and the quality of their interactions with prosecutors lead them to prepare more or less intensively for their court appearances.

Measurements of the linear energy transfer spectra on the Mir orbital station and comparison with radiation transport models

A tissue equivalent proportional counter designed to measure the linear energy transfer spectra (LET) in the range 0.2-1250 keV/micrometer was flown in the Kvant module on the Mir orbital station during September 1994. The spacecraft was in a 51.65 degrees inclination, elliptical (390 x 402 km) orbit. This is nearly the lower limit of its flight altitude. The total absorbed dose rate measured was 411.3 +/- 4.41 microGy/day with an average quality factor of 2.44. The galactic cosmic radiation (GCR) dose rate was 133.6 microGy/day with a quality factor of 3.35. The trapped radiation belt dose rate was 277.7 microGy/day with an average quality factor of 1.94. The peak rate through the South Atlantic Anomaly was approximately 12 microGy/min and nearly constant from one pass to another. A detailed comparison of the measured LET spectra has been made with radiation transport models. The GCR results are in good agreement with model calculations; however, this is not the case for radiation belt particles and again points to the need for improving the AP8 omni-directional trapped proton models.

In-flight radiation measurements on STS-60

A joint investigation between the United States and Russia to study the radiation environment inside the Space Shuttle flight STS-60 was carried out as part of the Shuttle-Mir Science Program (Phase 1). This is the first direct comparison of a number of different dosimetric measurement techniques between the two countries. STS-60 was launched on 3 February 1994 in a nearly circular 57 degrees x 353 km orbit with five U.S. astronauts and one Russian cosmonaut for 8.3 days. A variety of instruments provided crew radiation exposure, absorbed doses at fixed locations, neutron fluence and dose equivalent, linear energy transfer (LET) spectra of trapped and galactic cosmic radiation, and energy spectra and angular distribution of trapped protons. In general, there is good agreement between the U.S. and Russian measurements. The AP8 Min trapped proton model predicts an average of 1.8 times the measured absorbed dose. The average quality factor determined from measured lineal energy, y, spectra using a tissue equivalent proportional counter (TEPC), is in good agreement with that derived from the high temperature peak in the 6LiF thermoluminescent detectors (TLDs). The radiation exposure in the mid-deck locker from neutrons below 1 MeV was 2.53 +/- 1.33 microSv/day. The absorbed dose rates measured using a tissue equivalent proportional counter, were 171.1 +/- 0.4 and 127.4 +/- 0.4 microGy/day for trapped particles and galactic cosmic rays, respectively. The combined dose rate of 298.5 +/- 0.82 microGy/day is about a factor of 1.4 higher than that measured using TLDs. The westward longitude drift of the South Atlantic Anomaly (SAA) is estimated to be 0.22 +/- 0.02 degrees/y. We evaluated the effects of spacecraft attitudes on TEPC dose rates due to the highly anisotropic low-earth orbit proton environment. Changes in spacecraft attitude resulted in dose-rate variations by factors of up to 2 at the location of the TEPC.

Measurements of trapped protons and cosmic rays from recent Shuttle flights

We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we report on the dose rate, equivalent dose rate, and radiation quality factor for trapped protons and cosmic radiation separately. A comparison of the integral linear energy transfer (LET) spectra with recent transport code calculations show significant disagreement. Using the calculated dose rate from the omni-directional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of (averaged over all geographic latitude) and longitude, we have determined the westward drift of the South Atlantic anomaly. We have also studied the east-west effect, and observed a 'second' radiation belt. A comparison of the galactic cosmic radiation lineal energy transfer spectra with model calculations shows disagreement comparable to those of the trapped protons.

Recent space shuttle observations of the South Atlantic Anomaly and the radiation belt models

Active instruments consisting of a tissue equivalent proportional counter (TEPC) and a proton and heavy ion detector (PHIDE) have been carried on a number of Space Shuttle flights. These instruments have allowed us to map out parts of the South Atlantic Particle Anomaly (SAA) and to compare some of its features with predictions of the AP-8 energetic proton flux models. We have observed that consistent with the generally observed westward drift of the surface features of the terrestrial magnetic field the SAA has moved west by about 6.9 degrees longitude between the epoch year 1970 of the AP-8 solar maximum model and the Space Shuttle observations made twenty years later. However, calculations indicate that except for relatively brief periods following very large magnetic storms the SAA seems to occupy the same position in L-space as in 1970. After the great storm of 24 March 1991 reconfiguration of the inner radiation belt and/or proton injection into the inner belt, a second energetic proton belt was observed to form at L approximately = 2. As confirmed by a subsequent flight observations, this belt was shown to persist at least for six months. Our measurements also indicate an upward shift in the L location of the primary belt from L = 1.4 to L = 1.5. In addition we confirm through direct real time observations the existence and the approximate magnitude of the East-West effect.

Measurements on the shuttle of the LET spectra of galactic cosmic radiation and comparison with the radiation transport model

A new class of tissue-equivalent proportional counters has been flown on two space shuttle flights. These detectors and their associated electronics cover a lineal energy range from 0.4 to 1250 keV/microns with a multichannel analyzer resolution of 0.1 keV/microns from 0.4 to 20 keV/microns and 5 keV/microns from 20 to 1250 keV/microns. These detectors provide the most complete dynamic range and highest resolution of any technique currently in use. On one mission, one detector was mounted in the Shuttle payload bay and another older model in the mid-deck, thus providing information on the depth dependence of the lineal energy spectrum. A detailed comparison of the observed lineal energy and calculated LET spectra for galactic cosmic radiation shows that, although the radiation transport models provide a rather accurate description of the dose (+/- 15%) and equivalent dose (+/- 15%), the calculations significantly underestimate the frequency of events below about 100 keV/microns. This difference cannot be explained by the inclusion of the contribution of splash protons. The contribution of the secondary pions, kaons and electrons produced in the Shuttle shielding, if included in the radiation transport model, may explain these differences. There are also significant differences between the model predictions and observations above 140 keV/microns, particularly for 28.5 degrees inclination orbit.

Measurements of trapped protons and cosmic rays from recent Shuttle flights

Two new charged particle detectors have been flown in five recent Shuttle flights. The tissue-equivalent proportional counter measures the lineal energy spectrum of space radiation in the 0.26-300 keV micrometer-1 range. The charged particle spectrometer is a double dE/dx x E and dE/dx x Chrenekov detector system which provides a measurement of the differential energy spectrum of protons from 13 to 350 MeV and dose rate in silicon. In this paper the dose rate, equivalent dose rate, and radiation, quality factor for trapped protons and cosmic radiation are reported on separately. A comparison of the integral LET spectra with recent transport code calculations shows significant disagreement. Using the calculated dose rate from the omnidirectional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of geographic latitude and longitude, the westward drift of the south Atlantic anomaly has been determined. The east-west effect has also been studied and a 'second' radiation belt observed. A comparison of the galactic cosmic radiation (GCR) lineal energy transfer spectra with model calculations shows disagreement comparable with those of the trapped protons.

Active dosimetric measurements on shuttle flights

A tissue-equivalent proportional counter spectrometer capable of measuring the absorbed dose and dose distribution as a function of linear energy transfer (LET) and time, for all penetrating radiation in space, is described. This instrument weighs about 0.7 kg and was flown on the STS-31 (28.5 degrees x 620 km) flight of the Space Shuttle, 24-29 April 1990. The measured total dose is in excellent agreement with the calculations based on the AP8MAX model of the trapped radiation belt protons. The observed LET frequency distribution is also in excellent agreement with calculations based on this model. Active instruments can provide more detailed dosimetry for crew risk assessment than the thermoluminescent detectors or a plastic track detector system.

Effect of the Orbital Debris Environment on the High-Energy Van Allen Proton Belt

Orbital debris in the near-Earth environment has reached a number density sufficient for a significant collisional interaction with some of the long-lived high-energy protons in the radiation belt. As a result of a continuing buildup of a shell of man-made debris, the lifetimes of high-energy protons whose trajectories remain below 1500 kilometers will decrease to the point where in the next decades we can expect a noticeable reduction in their fluxes.