Association of cigarette smoking with changes in macroeconomic conditions

This study uses data from the 1987-2022 Behavioral Risk Factor Surveillance System and state-level employment rates from the US Bureau of Labor Statistics to estimate the association between macroeconomic conditions and cigarette smoking. Our finding suggests a positive association, which constantly declined with time after the 2001 recession. We find that a one percentage point increase in the employment rate is associated with a 1.4% higher likelihood of smoking cigarettes in the overall sample but declined to 0.4% among cohorts surveyed from 2011 to 2022. We also find strong positive and heterogeneous associations among sociodemographic groups, except among Blacks and persons aged 65 years and older, among whom there is no association; however, the positive associations consistently decreased among these sociodemographic groups. Consequently, the strong positive association disappeared in several sociodemographic groups in cohorts surveyed over the last decade.

Concept flavor e-cigarette unit sales in the U.S.: 2019-2022

Introduction

Concept flavor e-cigarettes, defined as products with vague/ambiguous flavor (tobacco flavor and non-tobacco flavor) names, may limit the intended impact and enforcement of flavored tobacco restrictions. This study assessed trends in unit sales of concept flavor e-cigarettes in the U.S. by volume, nicotine concentration levels (NCL), flavor and device type.

Methods

We analyzed NielsenIQ Retail Scanner point-of-sales data collected from 2182 Local Trade Areas in the contiguous 48 U.S. states and the District of Columbia aggregated weekly from August 10, 2019, through April 9, 2022. Concept flavors were categorized by: flavor type (tobacco, fruity, menthol, mint, and other); device type (pods/refillable cartridges, disposables, e-liquids, and other); and NCL (0 %-2.0 %, 2.1 %-4.0 %, > 4.1 %, unknown). Joinpoint regression was used to assess sales trends.

Results

Overall unit sales during the study period increased by 33.63 % from 1040.85 to 1390.88 thousand units per month (p = 0.006). Between August 2019 and September 2021, unit sales increased and peaked; between September 2021 and April 2022 sales decreased by 14.46 % (from 1626.02 to 1390.88 thousand units; p = 0.002). Sales of fruity, menthol and mint flavors concept flavor e-cigarettes increased by > 1000 %; disposable devices by 302.18 %; pods and refillable cartridges by 33.81 % overall; and products NCL > 4.0 % increased by 110.18 %. Tobacco flavor concept flavors (93.28 %), pods (94.63 %), and products with 2.1 %-4.0 % NCL (88.40 %) dominated unit share.

Conclusion

Sustaining the recent overall decline in the unit sales of concept flavor e-cigarettes and monitoring the sales of products with nicotine concentration greater than 2.0%, non-tobacco flavor, and pod products warrant prioritization in tobacco control efforts.

Trends in public interest in shopping and point-of-sales of JUUL and Puff Bar 2019-2021

INTRODUCTION

We investigated public interest in shopping and point-of-sales (POS) of JUUL and Puff Bar products in the context of five regulatory, company sales policy and other events of interest that may have influenced the trajectory of these products during 2019-2021.

METHODS

Outcome variables included relative search volume (RSV) from Google search queries indicative of shopping interest in and aggregate dollar sales from Nielsen POS for JUUL and Puff Bar in the USA from March 2019 to May 2021. Adjusted autoregressive integrated moving average assessed the observed and predicted trends and adjusted linear regression analysis measured the relative rate of change in the outcome variables for each time period of interest.

RESULTS

After the Trump administration announced its plans to ban flavoured e-cigarettes and JUUL Labs, Inc.'s decided to suspend the sales of its sweet and fruity flavoured products, JUUL's shopping interest RSV and sales declined while Puff Bar's shopping interest RSV peaked, and its sales increased. From the period following FDA's announcement of its enforcement guidance policy on unauthorised flavoured cartridge-based e-cigarettes until May 2021, JUUL's shopping interest RSV and sales continued to decline. Puff Bar's shopping interest RSV increased, and its sales peaked until the House approved the flavoured e-cigarette ban bill. Puff Bar's sales steeply declined following suspension of its sales in February 2020. The decline, however, slowed after Puff Bar products were relaunched as 'synthetic nicotine' e-cigarettes.

CONCLUSIONS

Puff Bar's unprecedented peak in the shopping interest and sales of Puff Bar warrants continued surveillance.

Association between cigarette sales in the USA and FDA's announcement of its intention to prohibit menthol as a characterising flavour in cigarettes

INTRODUCTION

On 29 April 2021, the US Food and Drug Administration (FDA) announced its intention to prohibit menthol as a characterising flavour in cigarettes.

METHODS

We assessed the changes in cigarette sales associated with the FDA's announcement using interrupted time series analysis based on monthly retail point-of-sale data on cigarettes from the NielsenIQ Local Trade Area (LTA) data from September 2019 to April 2022. Main outcome variables included LTA-level monthly menthol and non-menthol cigarette sales per 1000-persons.

RESULTS

Monthly cigarette sales were declining before the FDA's announcement (menthol vs non-menthol: -1.68 (95% CI -1.92, -1.45) vs -3.14 (95% CI -3.33, -2.96) packs per 1000-persons). Monthly menthol cigarette sales increased immediately in May 2021 after the FDA's announcement by 6.44 packs per 1000-persons (95% CI 3.83, 9.05). Analysis stratified by LTA-level racial/ethnic compositions showed that LTAs with a relatively higher proportion of non-Hispanic Black population (>8.94%) experienced higher spike in menthol cigarette sales in May 2021 immediately after the announcement and higher post-announcement 12-month menthol cigarette sales than expected.

CONCLUSIONS

Areas with a relatively higher proportion of non-Hispanic Black population are potentially at risk of experiencing increased burden of menthol cigarette consumption. Targeted community level cessation support in non-Hispanic Black majority areas may help mitigate the growing burden of menthol cigarette smoking and improve health equity. The findings of this study also suggest that FDA's prompt finalisation and enforcement of such ban may help avoid extending the increased burden of menthol cigarette consumptions in non-Hispanic Black majority areas.

Declining trend in cigarette smoking among U.S. adults over 2008-2018: A decomposition analysis

The United States (U.S.) witnessed considerable reduction in cigarette smoking prevalence in the recent past. While the correlates of smoking prevalence and related disparities among U.S. adults are well documented, there is limited information on how this success was shared among different population sub-groups. Based on data from the National Health Interview Surveys, 2008 and 2018, representative of non-institutionalized U.S. adults (18 years and above), we applied the threefold Kitawaga-Oaxaca-Blinder linear decomposition analysis. We decomposed the trends in cigarette smoking prevalence, smoking initiation, and successful cessation into changes in population characteristics holding smoking propensities constant (compositional change), changes in smoking propensities by population characteristics holding population composition constant (structural change), and the unmeasured macro-level changes affecting smoking behavior in different population sub-groups at differential rates (residual change) to quantify the shares of population sub-groups by sex, age, race/ethnicity, education, marital status, employment status, health insurance coverage, family income, and region of residence in the overall change in smoking rates. The analysis shows that decreases in smoking propensities regardless of the changes in population composition accounted for 66.4% of the reduction in smoking prevalence and 88.7% of the reduction in smoking initiation. The major reductions in smoking propensity were among Medicaid recipients and young adults (ages 18-24 years). The 25-44-year-olds experienced moderate increase in successful smoking cessation, while the overall successful smoking cessation rate remained steady. Taken together, consistent reduction in smoking among U.S. adults by all major population characteristics, accompanied by disproportionately larger reduction in smoking propensities among the population sub-groups with initially higher smoking propensity compared to the national average, characterized the decline in overall cigarette smoking. Strengthening proven tobacco control measures with targeted interventions to reduce smoking propensities among underserved populations is key to continued success in reducing smoking overall and remedying inequities in smoking and population health.

Association of nicotine replacement therapy product sales with menthol cigarette sales restriction in Massachusetts

BACKGROUND

Massachusetts was the first to implement a state-wide menthol cigarette sales restriction in the USA. Following its implementation in June 2020, evidence showed declines in cigarette sales in Massachusetts; however, changes in nicotine replacement therapy (NRT) product sales are unknown.

METHODS

This cohort study analysed NRT products sold by US-based retailers available in 26 states from the Nielsen Retail Scanner Data. Outcomes were state-level 4-week aggregate sales of gum, lozenge and patch NRT products converted into pieces per 1000 adults (aged ≥18 years) who smoke cigarettes based on smoking rates from the Behavioral Risk Factor Surveillance System and corresponding population from the US Census Bureau. We used a difference-in-differences method to compare changes in NRT product sales in Massachusetts before (1 January 2017 to 13 June 2020) and after (14 June 2020 to 4 December 2021) the policy with sales in 25 states.

RESULTS

The analysis included 1664 observations for each NRT product, with 1170 from before and 494 from after the policy change. The 4-week NRT product sales per 1000 adults who smoke cigarettes in Massachusetts compared with the comparison states increased for gums by 643.11 (95% CI 365.33 to 920.89; p<0.001) pieces or 12.9% and for lozenges by 436.97 (95% CI 292.88 to 581.06; p<0.001) pieces or 17.9% but no statistically significant change in patches after implementing the policy.

CONCLUSION

The increases in sales of gum and lozenge NRT products in Massachusetts after implementing the policy suggest that a nationwide ban on menthol cigarettes can increase NRT product use; therefore, interventions are needed to strengthen cessation support for adults who smoke cigarettes but intend to quit.

Association of Comprehensive Menthol Flavor Ban With Current Cigarette Smoking in Massachusetts From 2017 to 2021

This cross-sectional study compares self-reported smoking by adults before vs after prohibition of menthol-flavored cigarettes.

Changes in State-Level Cigarette Sales During the COVID-19 Pandemic

This cohort study estimates state-level changes in cigarette sales in the US during the COVID-19 pandemic.

Nicotine Pouch Sales Trends in the US by Volume and Nicotine Concentration Levels From 2019 to 2022

This cross-sectional study examines the sale of 4 nicotine pouch brands in the contiguous 48 states and Washington, DC.

Spatial Analysis of Changes in Cigarette Sales in Massachusetts and Bordering States Following the Massachusetts Menthol Flavor Ban

This cohort study examines changes in cigarette sales in Massachusetts and its bordering states following a comprehensive ban on menthol flavor in Massachusetts in 2020.

Person-years of life lost and lost earnings from cigarette smoking-attributable cancer deaths, United States, 2019

State-specific information on lost earnings due to smoking-attributable cancer deaths to inform and advocate for tobacco control policies is lacking. We estimated person-years of life lost (PYLL) and lost earnings due to cigarette smoking-attributable cancer deaths in the United States nationally and by state. Proportions and numbers of cigarette smoking-attributable cancer deaths and associated PYLL among individuals aged 25 to 79 years in 2019 were calculated and combined with annual median earnings to estimate lost earnings attributable to cigarette smoking. In 2019, estimated total PYLL and lost earnings associated with cigarette smoking-attributable cancer deaths in ages 25 to 79 years in the United States were 2 188 195 (95% CI, 2 148 707-2 231 538) PYLL and $20.9 billion ($20.0 billion-$21.7 billion), respectively. States with the highest overall age-standardized PYLL and lost earning rates generally were in the South and Midwest. The estimated rate per 100 000 population ranged from 352 (339-366) in Utah to 1337 (1310-1367) in West Virginia for PYLL and from $4.3 million ($3.5 million-$5.2 million) in Idaho to $14.8 million ($10.6 million-$20.7 million) in Missouri for lost earnings. If age-specific PYLL and lost earning rates in Utah had been achieved by all states, 58.2% (57.0%-59.5%) of the estimated total PYLL (1 274 178; 1 242 218-1 306 685 PYLL) and 50.5% (34.2%-62.4%) of lost earnings ($10.5 billion; $7.1 billion-$13.1 billion) in 2019 nationally would have been avoided. Lost earnings due to smoking-attributable cancer deaths are substantial in the United States and are highest in states with weaker tobacco control policies.

Changes in Smoking Cessation-Related Behaviors Among US Adults During the COVID-19 Pandemic

IMPORTANCE

Smoking cessation is an urgent public health priority given that smoking is associated with increased risk of severe COVID-19 outcomes and other diseases. It is unknown how smoking cessation changed nationally during the COVID-19 pandemic.

OBJECTIVE

To investigate changes in smoking cessation-related behaviors in the US during the COVID-19 pandemic.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study was conducted using 2011 to 2020 data on 788 008 individuals who had smoked in the past year from the nationally representative Behavioral Risk Factor Surveillance System (BRFSS) survey. Representative retail scanner sales data between January 2017 and July 2021 for 1004 unique nicotine replacement therapy (NRT) universal product codes in 31 US states from NielsenIQ were also used.

EXPOSURES

Calendar year and 4-week sales periods.

MAIN OUTCOMES AND MEASURES

Changes in annual self-reported prevalence of past-year quit attempts and recent successful cessation before (ie, 2011-2019) and during (ie, 2020) the COVID-19 pandemic and changes in sales volumes in millions of pieces of nicotine gum, lozenge, and patch brands before (1271 four-week sales periods between January 2017 and February 2020) and during (558 four-week sales periods between March 2020 and July 2021) the COVID-19 pandemic were calculated.

RESULTS

The 2011 to 2020 pooled BRFSS sample (response rate range, 45.2%-49.9%) included 788 008 respondents (243 061 individuals ages 25-44 years [weighted percentage, 42.5%]; 374 519 men [weighted percentage, 55.7%]). For the first time since 2011, annual past-year quit attempt prevalence decreased between 2019 and 2020, from 65.2% (95% CI, 64.5% to 65.9%) to 63.2% (95% CI, 62.3% to 64.0%), with the largest relative decreases among individuals ages 45 to 64 years (61.4% [95% CI, 60.3% to 62.5%] vs 57.7% [95% CI, 56.3% to 59.2%]), those with 2 or more comorbidities (67.1% [95% CI, 66.0% to 68.2%] to 63.0% [95% CI, 61.6% to 64.4%]), and Black individuals (72.5% [95% CI, 70.3 to 74.6] vs 68.4% [95% CI, 65.3% to 71.3%]). Recent successful cessation remained unchanged during 2019 to 2020. Observed mean (SD) 4-week NRT sales volume in the prepandemic period was 105.6 (66.2) million gum pieces, 51.9 (31.6) million lozenges, and 2.0 (1.1) million patches. Compared with expected sales, observed sales during the COVID-19 pandemic were lower by 13.0% (95% CI, -13.7% to -12.3%) for lozenges, 6.4% (95% CI, -7.3% to -5.5%) for patches, and 1.2% (95% CI, -1.7% to -0.7%) for gum.

CONCLUSIONS AND RELEVANCE

This study found that serious smoking cessation activity among US adults decreased immediately and remained depressed for more than a year during the COVID-19 pandemic. These findings suggest that smokers experiencing disproportionately negative outcomes during the pandemic should be reengaged and assisted in quit attempts.

Relative Harm Perceptions of E-Cigarettes Versus Cigarettes, U.S. Adults, 2018-2020

INTRODUCTION

It is unknown how U.S. adults' relative harm perceptions of E-cigarettes versus cigarettes and associated behaviors changed during the E-cigarette or vaping product use‒associated lung injury epidemic (late 2019) and COVID-19 pandemic (since early 2020).

METHODS

Data from cross-sectional nationally representative Health Information National Trends Survey collected in 2018 (n=3,360), 2019 (n=3,217), and 2020 (n=3,677) (analyzed in 2021) were used to estimate changes in relative harm perceptions of E-cigarettes versus cigarettes (less harmful, as harmful, more harmful, don't know as a measure of uncertainty). In addition, changes in exclusive cigarette smoking, exclusive E-cigarette use, and dual use were estimated for each relative harm perception level.

RESULTS

Perceptions of E-cigarettes as more harmful than cigarettes doubled year on year, increasing most between 2019 and 2020 (2018: 6.8%, 2019: 12.8%, 2020: 28.3%), whereas uncertainty in relative harm declined (2018: 38.2%, 2019: 34.2%, 2020: 24.7%). Less harmful relative perceptions declined (2018:17.6%, 2019:15.3%, 2020:11.4%), whereas as harmful perceptions remained steady (2018: 37.4%, 2019: 37.7%, 2020: 35.6%). Exclusive cigarette smoking increased between 2019 and 2020 among those who perceived E-cigarettes as relatively more harmful (2018: 18.5%; 2019: 8.4%; 2020: 16.3%), exclusive E-cigarette use increased linearly among those who perceived them as relatively less harmful (7.9%, 15.3%, 26.7%), and dual use increased linearly in those who perceived them relatively as harmful (0.1%, 1.4%, 2.9%).

CONCLUSIONS

Perceptions of E-cigarettes as more harmful than cigarettes increased sharply between 2019 and 2020. Increases in tobacco product use were potentially guided by product-specific relative harm perceptions because changes occurred primarily in individuals who perceived their preferred product as relatively less harmful, suggesting the need for accurate messaging of relative and absolute product risks.

COVID-19 and Tweets About Quitting Cigarette Smoking: Topic Model Analysis of Twitter Posts 2018-2020

Background

The risk of infection and severity of illness by SARS-CoV-2 infection is elevated for people who smoke cigarettes and may motivate quitting. Organic public conversations on Twitter about quitting smoking could provide insight into quitting motivations or behaviors associated with the pandemic.

Objective

This study explored key topics of conversation about quitting cigarette smoking and examined their trajectory during 2018-2020.

Methods

Topic model analysis with latent Dirichlet allocation (LDA) identified themes in US tweets with the term “quit smoking.” The model was trained on posts from 2018 and was then applied to tweets posted in 2019 and 2020. Analysis of variance and follow-up pairwise tests were used to compare the daily frequency of tweets within and across years by quarter.

Results

The mean numbers of daily tweets on quitting smoking in 2018, 2019, and 2020 were 133 (SD 36.2), 145 (SD 69.4), and 127 (SD 32.6), respectively. Six topics were extracted: (1) need to quit, (2) personal experiences, (3) electronic cigarettes (e-cigarettes), (4) advice/success, (5) quitting as a component of general health behavior change, and (6) clinics/services. Overall, the pandemic was not associated with changes in posts about quitting; instead, New Year’s resolutions and the 2019 e-cigarette or vaping use–associated lung injury (EVALI) epidemic were more plausible explanations for observed changes within and across years. Fewer second-quarter posts in 2020 for the topic e-cigarettes may reflect lower pandemic-related quitting interest, whereas fourth-quarter increases in 2020 for other topics pointed to a late-year upswing.

Conclusions

Twitter posts suggest that the pandemic did not generate greater interest in quitting smoking, but possibly a decrease in motivation when the rate of infections was increasing in the second quarter of 2020. Public health authorities may wish to craft messages for specific Twitter audiences (eg, using hashtags) to motivate quitting during pandemics.

Association of Cigarette Sales With Comprehensive Menthol Flavor Ban in Massachusetts

This cohort study examines whether cigarette sales changed after Massachusetts banned menthol-flavored tobacco products.

Abstract PR-01: Association of Affordable Care Act Medicaid expansions with healthcare access and utilization among people who smoke

Background: People who smoke have a higher risk of developing cancer and disproportionately lower incomes which worsens healthcare access and health outcomes. The Affordable Care Act expanded Medicaid eligibility to adults with income up to 138% of the federal poverty line. It is unknown if and how Medicaid expansions changed healthcare access, preventive service use, and health behaviors. Also, it is unknown whether expansions impacted income or racial/ethnic disparities in these measures, given historically lower healthcare access and utilization in lower income people and people of color. Methods: Data were from the nationally representative Behavioral Risk Factor Surveillance System surveys between 2011-2019 of adults ages 18-64 years who currently smoked cigarettes and former smokers who had quit in the past year (n=580,858). Generalized difference-in-differences (DID) analyses using logistic regression models examined the association of Medicaid expansions (staggered time-varying exposure, 34 states expanded as of December 2019) with healthcare access (insurance coverage, care affordability, usual source of care), preventive service use (routine checkup, flu shot, HIV test, breast and colorectal cancer screening, cholesterol check, dentist visit), and health/risk behaviors (heavy alcohol drinking, obesity), including cessation behaviors (past-year quit attempt, successful cessation for &gt;3 months). Income and race/ethnicity differences were also tested. Results: Among people who smoke, Medicaid expansions were associated with healthcare access and preventive care utilization improvements, but not health behaviors, including cessation. Expansions resulted in narrowing of disparities in several measures across income levels and Black vs. White people in expansion states. For example, expansion associated gains in insurance coverage were significantly larger in low-income (expansion: 74.6% vs. nonexpansion: 60.8%; DID: 13.8% 95% CI: 12.8, 14.8%) than high-income (insurance: 87.5% vs. 93.7%, DID: -6.2% points 95% CI: -7.2, -5.2%); and in Black people (82.6% vs. 74.6%, DID: 7.9% points 95% CI: 6.3, 9.5%) than White people (79.5% vs. 75.7%; DID: 3.8%, 95% CI: 3, 4.6%). Medicaid expansions gains were also larger among lower than higher income people for all in preventive care utilization measures studied; and uptake of flu shots, mammograms, and HIV tests were larger in Black than White people. Significant gains in multiple measures were also observed for Hispanic and American Indian/Alaska Native people who smoke, but changes were generally no different than White people. Conclusions: Among people who smoke, Medicaid expansions improved healthcare access and preventive services use. Expansions were also associated with a reduction, but not elimination, of income and Black-White disparities in healthcare access and utilization. Despite insurance and preventive service gains, expansions were not associated with cessation behaviors, signaling the need for improving comprehensive cessation treatments in Medicaid expansion programs.

Citation Format: Priti Bandi, Samuel Asare, J. Lee Westmaas, Nigar Nargis, Robin Yabroff, Ahmedin Jemal, Xuesong Han, Stacey Fedewa. Association of Affordable Care Act Medicaid expansions with healthcare access and utilization among people who smoke [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PR-01.

Association of teleworking and smoking behavior of U.S. wage and salary workers

INTRODUCTION

The COVID-19 pandemic has led to a major shift in workspace from office to home. This report examined how telecommuting is related to smoking behavior of wage and salary workers.

METHODS

Self-reported smoking behavior of 1,390 U.S. wage and salary workers aged 16-64 years from the Tobacco Use Supplement of the Current Population Survey 2018/19 were linked to the 2018 American Time Use Survey. Weighted multivariate logistic regression predicting smoking probability and generalized linear regression predicting smoking intensity were used for analysis.

RESULTS

Almost a fifth (19%) of wage and salary workers reported working from home and over a half (52%) reported working in telecommuting amenable occupations. Nearly 12% were current smokers, smoking 14.7 cigarettes daily on average. Compared to their counterparts, smoking prevalence (percentage points) was lower among those employed in telecommuting amenable occupations (-0.52, p < .001 for all; 0.01, p = .862 for men; -2.40, p < .001 for women) and who worked more frequently from home (-0.21, p < .001 for all; -0.76, p < .001 for men; -0.03, p = .045 for women). Smoking intensity (cigarettes per day) was lower among those employed in telecommuting amenable occupations (-3.39, p = .03 for all; -0.36, p = .90 for men; -4.30, p = .21 for women). We found no statistically significant association between smoking intensity and telecommuting frequency.

CONCLUSIONS

The lower likelihood of smoking and lower level of smoking intensity among telecommuting wage and salary workers suggests the need for proactive efforts to address the potential exacerbation in occupation-related smoking disparities between occupations that are and are not amenable to telecommuting.

Correction to: In vivo digestibility of six selected fodder species by goats in northern Ghana

The article "In vivo digestibility of six selected fodder species by goats in northern Ghana," written by F. K. Avornyo et al., was originally published electronically on the publisher's internet portal (currently SpringerLink) on 13 July 2019 without open access.

Effects of Prices on Youth Cigarette Smoking and Tobacco Use Initiation in Ghana and Nigeria

Background: Population growth in the African region is set to outpace the rate of decline in smoking prevalence, leading to a projected increase in the total number of smokers. As most tobacco users initiate during their adolescent years, tobacco prevention strategies targeting youth will be particularly important. Methods: This study estimated the impact of cigarette prices on youth cigarette smoking and tobacco use initiation in Ghana and Nigeria using the Global Youth Tobacco Survey data. First, we used cross-section data and logit models to estimate the effects of prices on youth cigarette smoking. Second, we created pseudo longitudinal data and used continuous-time hazard models to evaluate the impact of cigarette prices on tobacco use initiation. Results: We found that higher cigarette prices decreased both 30-day cigarette smoking and tobacco use onset significantly in both Ghana and Nigeria. Additionally, the price elasticity of cigarette smoking and tobacco use initiation ranged from -0.44 to -1.13, and -1.04 to -3.66, respectively. Conclusions: As one of the first studies on youth tobacco consumption in Sub-Saharan Africa, this study strongly suggests that policies that increase real cigarette prices can lower both cigarette smoking and tobacco use initiation among youth in Ghana and Nigeria.

In vivo digestibility of six selected fodder species by goats in northern Ghana

An in vivo digestibility trial was conducted to evaluate the digestibility of six forages. These were selected indigenous browse species and groundnut haulms in Lawra and Jirapa Districts of the Upper West Region of Ghana. Groundnut haulms served as a control due to its known good digestibility in small ruminants. Thirty West African Dwarf (WAD) young castrated billy goats with a mean age of 8 months were used. The average live body weight was 8.9 ± 0.1 kg. The animals were randomly assigned to the six treatments and replicated five times in a completely randomized design. They were confined in metabolism cages. The adaptation period was 3 weeks after which data was taken for 10 days. The treatments were the leaves and tiny twigs of T1 Annona senegalensis, T2 Ficus gnaphalocarpa, T3 Pericopsis laxiflora, T4 Pterocarpus erinaceus, T5 Afzelia africana, and T6 (control) Arachis hypogaea. Feed intake, faecal matter and urine output were measured. The results indicated that dry matter (DM) contents of the feedstuffs were less than 50% but crude protein (CP) contents were higher than the minimum required for sustaining ruminants. Neutral and acid detergent fibre contents were high, and F. gnaphalocarpa, in particular, contained a higher level of phosphorus (P). The amounts of feed intakes were typical of most fodder species with the exception of P. laxiflora and P. erinaceus, which were lower (P < 0.05). The apparent digestibility values were also typical of most fodder species but the digestibility of A. africana fibre appeared to be lower. Nitrogen retention was positive for all test species with the exception of P. laxiflora, which was negative. Mortality was recorded in animals on P. laxiflora, and the rate was high. Pericopsis laxiflora leaves, even though morphologically similar to the leaves of P. erinaceus, were not a suitable fodder. Ficus gnaphalocarpa appeared to be the overall best fodder species in terms of nutrient uptake.

Abstract PD4-04: Role of breast MRI in predicting pathologically negative nodes after neoadjuvant chemotherapy in cN0 patients in the I-SPY2 trial

Background

In clinically node-negative (cN0) breast cancer patients with triple negative (TN) and HER2+ disease and breast pathological complete response (breast pCR), low rates of nodal positivity after neoadjuvant chemotherapy (NAC) have been demonstrated. In these patients, the omission of surgical axillary staging has been proposed. However, this information is not routinely known preoperatively. We aimed to validate the correlation between pathologic breast response and pathologic nodal status, and evaluate the relationship between response of the breast tumor on MRI and pathologic nodal status after NAC in cN0 patients in the I-SPY2 trial.

Methods

We identified all patients with cT1-4 cN0 breast cancer prior to NAC from graduated arms of the I-SPY2 trial, a prospective neoadjuvant chemotherapy trial. Absence of residual disease post-NAC was defined as longest diameter (LD) of 0 mm on MRI. Breast pCR was defined as the absence of invasive tumor in the breast at surgery. Associations between ypN0 and patient, MRI, and tumor characteristics were assessed using chi-square tests and univariate regression.

Results

Of 365 cT1-4 cN0 patients included, 128 had HR+/HER2- tumors (35%), 60 HR+/HER2+ tumors (16%), 34 HR-/HER2+ tumors (9%) and 143 TN tumors (39%). Overall, 283 patients (78%) were ypN0 after NAC and 152 patients (42%) had a breast pCR. ypN0 rate was higher in patients with a breast pCR than those with residual disease (93% vs 66%, p&lt;0.001). Patients with HR-/HER2+ and TN tumors were more likely to be ypN0 (97% and 87% respectively) than patients with HR+/HER2- and HR+/HER2+ disease (66% and 71% respectively, p&lt;0.001). Other characteristics associated with ypN0 were tumor grade (grade I 57%, grade II 66%, grade III 84%; p=0.002), MammaPrint Classification (High Risk 1 68% and High Risk 2 87%; p&lt;0.001) and absence of residual tumor in the breast on MRI (87% vs 72% in patients with evidence of tumor on MRI post-NAC/pre-surgery; p=0.003).

In patients with HR-/HER2+, HR+/HER2+, HR-/HER2+ or TN disease and a breast pCR, ypN0 rate was respectively 82%, 96%, 96% and 97% (table 1). In patients with HR+/HER2-, HR+/HER2+, HR-/HER2+ or TN disease and with no evidence of residual disease in the breast on MRI, rate of ypN0 was 71%, 80%, 94% and 96% respectively.

Conclusion

In cT1-4 cN0 breast cancer patients with HR+/HER2+, HR-/HER2+ and TN tumors and a breast pCR, ypN0 rates after NAC are extremely high. In patients with HR-/HER2+ and TN tumors with no residual breast disease on MRI after NAC and pre-surgery, ypN0 rates are high enough to consider omission of axillary surgery. In patients with HR+ tumors, MRI is unsufficiently predictive for pathological response and can therefore not be used to select ypN0 patients. Research on the prediction of ypN0 in cN+ I-SPY2 patients is ongoing.

Nodal status in patients with pCR and absence of residual disease on MRI Number of positive nodesBreast Cancer Subtype0123AllBreast pCR     HR+/HER2-27(82)2(6)4(12)033(100)HR+/HER2+24(96)01(4)025(100)HR-/HER2+24(96)1(4)0025(100)TN67(97)2(3)0069(100)Absence of residual disease on MRI     HR+/HER2-24(71)7(21)3(9)034(100)HR+/HER2+16(80)3(15)01(5)20(100)HR-/HER2+15(94)1(6)0016(100)TN54(96)2(4)0056(100)

Citation Format: van der Noordaa ME, Esserman L, Yau C, Mukhtar R, Price E, Hylton N, Abe H, Wolverton D, Crane EP, Ward KA, Nelson M, Niell BL, Oh K, Brandt KR, Bang DH, Ojeda-Fournier H, Eghtedari M, Sheth PA, Bernreuter WK, Umphrey H, Rosen MA, Dogan B, Yang W, Joe B, van 't Veer L, Hirst G, Lancaster R, Wallace A, Alvaredo M, Symmans F, Asare S, Boughey JC, I-SPY2 Consortium. Role of breast MRI in predicting pathologically negative nodes after neoadjuvant chemotherapy in cN0 patients in the I-SPY2 trial [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD4-04.

Abstract P1-15-02: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Schwab R, Clark A, Yau C, Wolf D, Chien AJ, Majure M, Ewing C, Wallace A, Roesch E, Helsten T, Forero A, Stringer-Reasor E, Vaklavas C, Nanda R, Jaskowiak N, Boughey J, Haddad T, Han H, Lee C, Albain K, Isaacs C, Elias A, Ellis E, Shah P, Lang J, Lu J, Tripathy D, Kemmer K, Yee D, Haley B, Korde L, Edmiston K, Northfelt D, Viscusi R, Khan Q, I-SPY 2 Consortium, Symmans WF, Perlmutter J, Hylton N, Rugo H, Melisko M, Wilson A, Singhrao R, Asare S, van't Veer L, DeMichele A, Berry D, Esserman L. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-15-02.

Abstract P3-10-14: LIV-1 expression in primary breast cancers in the I-SPY 2 TRIAL

Background: LIV-1 is an estrogen-inducible gene that has been implicated in epidermal-to-mesenchymal transition (EMT) in preclinical models of progression and metastasis. Its expression is associated with node-positivity in breast cancer; and has been detected in a variety of cancer types, including estrogen receptor positive breast cancers. SGN-LIV1A is a novel antibody drug conjugate targeting LIV-1 that is currently being evaluated in the I-SPY 2 TRIAL. In this pilot study, we evaluated LIV-1 levels by IHC within HR/HER2/MammaPrint (MP) defined subtypes among patients screening for the I-SPY 2 TRIAL and its correlation to microarray assessed LIV-1 expression levels.

Method: In a pilot study, LIV-1 IHC staining was performed by Quest Diagnostics on the pre-treatment samples of 38 patients screening for the I-SPY 2 TRIAL. Pre-treatment expression data generated on a custom Agilent 44K platform was also available. We summarized the LIV-1 H-Scores and percent (%)-positivity across the population and within HR/HER2/MP subtypes; and we assessed the Pearson correlation between LIV-1 H-Score and LIV-1 gene expression levels. In addition, we compared the pre-treatment LIV-1 expression levels within HR/HER2/MP subtypes across I-SPY 2 TRIAL patients from completed arms and their relevant controls (n=989) using ANOVA and post-hoc Tukey tests. Our statistics are descriptive rather than inferential; and does not take into account multiplicities of other biomarkers outside of this study.

Results: Of the 38 patients evaluated, 37 have LIV-1 %-positivity &gt; 0; and 18 (47%) have 100% LIV1 positivity. The median LIV-1 H-Score is 200; and 89% of patients (34/38) have moderate/high LIV-1 staining (with H-Score≥100). Of the 34 patients who proceeded onto the trial (and have known HR/HER2/MP status), 9 are triple negative, 19 are HR+HER2-, and 6 are HER2+. Due to our small sample size, we did not further subset the triple negative and HER2+ cases; but within the HR+HER2- patients, 10 are MP1 compared to 9 who are MP2 class. LIV1 H-Score appears highest within the HR+HER2-MP1 cases (median: 290), followed by the HER2+ (median: 216), then the HR+HER2-/MP2 (median: 155), and the TN (median: 120) subtype. LIV1 H-score is significantly correlated with LIV-1 mRNA expression levels (Rp=0.79, p&lt;0.0001). Consistent with these observations, LIV-1 pre-treatment expression levels are significantly higher in the HR+HER2-MP1 group relative to all other HR/HER2/MP defined subtypes (Tukey HSD p &lt; 0.0001) across the I-SPY 2 TRIAL population. The HR+HER2+MP1 group also have high LIV-1 expression levels.

Conclusion: Our result suggest that although LIV-1 expression differs by subtype, it is expressed at a moderate/high level in the majority of patients. The good correlation between IHC and array-based LIV-1 expression levels enables us to leverage the entire existing I-SPY 2 dataset and confirm the high rates of LIV-1 expression across the I-SPY 2 population. Further studies to evaluate LIV-1 expression as a biomarker of response to LIV-1 targeting therapies for the neoadjuvant treatment of breast cancer are warranted and ongoing in I-SPY 2.

Citation Format: Yau C, Brown-Swigart L, Asare S, I-SPY 2 TRIAL Consortium, Esserman L, van' t Veer L, Beckwith H, Forero A, Rugo H. LIV-1 expression in primary breast cancers in the I-SPY 2 TRIAL [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-10-14.

Abstract P3-10-02: Identifying breast cancer molecular phenotypes to predict response in a modern treatment landscape: Lessons from ˜1000 patients across 10 arms of the I-SPY 2 TRIAL

Background: The explosion in new treatment options targeting immune checkpoints, HER signaling, DNA repair deficiency, AKT, and other pathways calls for updated breast cancer subtypes beyond HR and HER2 status to predict which patients will respond to which treatments. Here we leverage the I-SPY 2 TRIAL biomarker program over the past 8 years across 10 treatment arms to elucidate a minimal set of biomarkers that may improve response prediction in a modern treatment context, and to investigate which new patient phenotypes are identified by these response-predictive biomarkers.

Methods: 986 patients were considered in this analysis. Treatments included paclitaxel alone (or with trastuzumab (H) in HER2+) or combined with investigational agents: veliparib/carboplatin (VC); neratinib; MK2206; ganitumab; ganetespib; AMG386; TDM1/pertuzumab (P); H/P; and pembrolizumab (Pembro). 24 prospectively defined, mechanism-of-action and pathway-based expression and phospho-protein signatures/biomarkers assayed from pre-treatment biopsies were previously found to be predictive in a particular agent/arm in pre-specified analysis. Here we evaluate these biomarkers in all patients. We assessed association between each biomarker and response in the population as a whole and within each arm and HR/HER2 subtype using a logistic model. To identify optimal dichotomizing thresholds for select biomarkers, 2-fold cross-validation was repeated 500 times. Our analysis is exploratory and does not adjust for multiplicities.

Results: Our initial set of 24 predictive biomarkers reflects DNA repair deficiency (n=2), immune activation (n=7), ER signaling (n=2), HER2 signaling (n=4), proliferation (n=2), phospho-activation of AKT/mTOR (n=2), and ANG/TIE2 (n=1) pathways, among others. Biomarkers reflecting similar biology are correlated and cluster together. We make use of this correlation structure to reduce the dimensionality of the biomarker set to five predictive signals: proliferation, DNA repair deficiency (DRD), immune-engaged (Immune+), luminal/ER (lum), and HER2-activated. These biomarkers, when dichotomized, identify patient groups with differential predicted sensitivities to I-SPY 2 agents and are present at different proportions within receptor subtypes. For instance, in the HER2- subset, Immune+/DRD+ patients are predicted sensitive to both VC and Pembro, and account for 39% of TN, but only 12% of HR+HER2-. On the other end of the spectrum, only 17% of TN are Immune-/DRD-, compared to the majority (56%) of HR+HER2-. There are also subsets of patients positive for only one marker. For the HER2+ subset, 67% are HER2-activated+, and 25% lum+; of these HER2-activated+ patients are more likely to be Immune+ (44%), vs 23% in lum+. HER2-activated+/Immune+ patients have higher predicted sensitivity to HER2-targeted agents than lum+ or Immune- patients.

In all, these molecular phenotypes predict sensitivity to one or more I-SPY 2 investigational agents for 75% of the ˜ 1000 patients.

Conclusion: Molecular phenotypes reflecting proliferation, immune engagement, HER2-activation, luminal/ER-signaling, and DNA repair deficiency may provide a roadmap to guide treatment prioritization for emerging therapeutics.

Citation Format: Wolf DM, Yau C, Wulfkuhle J, Petricoin E, Campbell M, Brown-Swigart L, Hirst G, Asare S, Zhu Z, Lee EP, Delson A, Pohlmann P, I-SPY 2 TRIAL Consortium, Hylton N, Liu MC, Symmans F, DeMichele A, Yee D, Berry D, Esserman L, van 't Veer L. Identifying breast cancer molecular phenotypes to predict response in a modern treatment landscape: Lessons from ˜1000 patients across 10 arms of the I-SPY 2 TRIAL [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-10-02.

Abstract PD6-08: Analysis of immune infiltrates (assessed via multiplex fluorescence immunohistochemistry) and immune gene expression signatures as predictors of response to the checkpoint inhibitor pembrolizumab in the neoadjuvant I-SPY 2 trial

Background: Pembrolizumab (Pembro), an anti-PD-1 immune checkpoint inhibitor, has been approved for the treatment of a variety of cancers including melanoma, non-small cell lung cancer, head and neck squamous cell carcinoma, and urothelial carcinoma. Pembro was recently evaluated in HER2- breast cancer patients in the neoadjuvant I-SPY 2 TRIAL and graduated in the triple negative (TN), HR+HER2-, and HER2- signatures. HER2- patients were randomized to receive Pembro+paclitaxel followed by doxorubicin/cyclophosphamide (P+T -&gt; AC) vs. T -&gt; AC. We and others have shown that TN breast cancers tend to have high numbers of immune infiltrates, including T cells and tumor associated macrophages (TAMs). We evaluated expression signatures representing 14 immune cell types (TILs, T cells, CD8 T cells, exhausted T cells, Th1, Tregs, cytotoxic cells, NK, NK CD56dim, dendritic cells, mast cells, B cells, macrophages, and neutrophils) as specific predictors of response to Pembro.

Methods: Data from 248 patients (Pembro: 69; controls: 179) were available. Pre-treatment biopsies were assayed using Agilent gene expression arrays. Signature scores are calculated by averaging cell type specific genes. All I-SPY 2 qualifying biomarker analyses follow a pre-specified analysis plan. We used logistic modeling to assess biomarker performance. A biomarker is considered a specific predictor of Pembro response if it associates with response in the Pembro arm but not the control arm, and if the biomarker x treatment interaction is significant (likelihood ratio test, p&lt;0.05). This analysis is also performed adjusting for HR status as covariates, and within receptor subsets. For successful biomarkers, we use Bayesian modeling to estimate the pCR rates of 'predicted sensitive' patients in each arm. Our statistics are descriptive rather than inferential and do not adjust for multiplicities of other biomarkers outside this study.

Results: 10 out of the 14 cell-type signatures tested are associated with response in the Pembro arm. Higher expression levels of 9 of these cell-type signatures are associated with higher pCR rates (T cells, exhausted T cells, Th1, cytotoxic cells, NK, NK CD56dim, dendritic cells, B cells, and macrophages), whereas higher mast cell signature expression is associated with non-pCR. Interestingly, many of these same signatures also associate or trend towards association with response in the control arm; and in a model adjusting for HR status, only 3 of these signatures (Th1, B cells and dendritic cells) show significant interaction with treatment. Within the whole population and the TN subtype, the dendritic cell signature is the strongest predictor of specific response to Pembro (OR/1SD: 4.04 and 4.4, LR p &lt; 0.001 overall and in TN). Although other immune signatures (T cells, exhausted T cells, NK, and macrophages) also associate with response in the Pembro arm in the TN subtype, only the dendritic cell and Th1 signatures have a significant interaction with treatment. In contrast, in the HR+HER2- subtype, only 3 signatures (Th1, B cells, and mast cells) associate with response to Pembro; but none of these signatures have significant interaction with treatment. Of note, in both the Pembro and control arms, HR+HER2- patients with higher average mast cell marker expression have lower pCR rates (OR/1SD: 0.33 and 0.51, LRp: 0.006 and 0.04 in Pembro and control arm).

Conclusion: As expected, multiple immune cell expression signatures are predictive of response in the Pembro arm; but only dendritic cells and Th1 cells are specific to Pembro in both the population as a whole and the TN subtype. Interestingly, the presence of mast cells may impede response, especially in HR+HER2- patients. Correlation of these signatures with multiplex-IF immune markers is pending.

Citation Format: Campbell M, Yau C, Borowsky A, Vandenberg S, Wolf D, Rimm D, Nanda R, Liu M, Brown-Swigart L, Hirst G, Asare S, van't Veer L, Yee D, DeMichele A, Berry D, Esserman L. Analysis of immune infiltrates (assessed via multiplex fluorescence immunohistochemistry) and immune gene expression signatures as predictors of response to the checkpoint inhibitor pembrolizumab in the neoadjuvant I-SPY 2 trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD6-08.

Abstract PD6-14: Analysis of DNA repair deficiency biomarkers as predictors of response to the PD1 inhibitor pembrolizumab: Results from the neoadjuvant I-SPY 2 trial for stage II-III high-risk breast cancer

Background: Pembrolizumab (P), an anti-PD-1 immune checkpoint inhibitor, has been approved for treatment of microsatellite instability-high and mismatch repair deficient cancers. In I-SPY 2, patients were randomized to receive standard chemotherapy alone or in combination with an experimental agent. P was one of the experimental agents evaluated in HER2- patients in I-SPY 2 and graduated in the TN, HR+HER2-, and HER2- signatures. We hypothesize that a combination of two signatures predicting response to veliparib/carboplatin therapy in I-SPY 2 [MammaPrint High2 (MP2)/PARPi7-high] and reflecting DNA damage repair deficiency, may also predict response to P. In addition, we also tested 9 gene expression signatures reflecting different aspects of DNA damage and repair: FA, MMR, BER, HR, TLS, NER, NHEJ, DR, and DNA damage sensing (DDS) pathways.

Methods: Data from 249 patients (P: 69 and controls: 180) were available. Pre-treatment biopsies were assayed using Agilent gene expression arrays. All I-SPY 2 qualifying biomarker analyses follow a pre-specified analysis plan. We used logistic modeling to assess biomarker performance. A biomarker is considered a specific predictor of P response if it associates with response in the P arm but not the control arm, and if the biomarker x treatment interaction is significant (likelihood ratio test, p&lt;0.05). This analysis is also performed adjusting for HR status as a covariate, and within receptor subsets, sample size permitting. For successful biomarkers, we use Bayesian modeling to estimate the pCR rates of 'predicted sensitive' patients in each arm. Our statistics are descriptive rather than inferential and do not adjust for multiplicities of other biomarkers outside this study.

Results: MP2 status associates with pCR in P (OR=7.7; p=0.00021), but also to a lesser extent in the control arm (OR=2.4:p=0.045), with an OR ratio of 3.3 which trends toward significance, even after adjusting for HR status (LR p=0.083). A majority of TN patients are MP2; and TN/MP2 patients have an estimated pCR rate of 67% in P (vs. 23% in control). Although only ~30% of HR+HER2- patients were MP2, their estimated pCR rate in P is 61%, compared to 29% in unselected HR+/HER2- patients. PARPi7 predicted response in the P arm only in the HR+HER2- group (LR p= 0.025), but not in the population as a whole or the TN subtype. Combining MP2 and PARPi7 into MP2/PARPi7-high did not improve performance over MP2 as a single biomarker. Of the 9 DDR pathway signatures tested, both BER and DDS associate with pCR in P, but only DDS (which includes ATM, ATR, CHEK1-2) associates with pCR in the P arm (LR p=0.00029), and not the control arm (LR p=0.53), with a significant interaction with treatment (LR p=0.0064) that retains significance in a model adjusting for HR status. When dichotomized to optimize the biomarker x treatment interaction, the estimated pCR rate is 75% in P vs 18% in control, in the DDS+ subset.

Conclusion: In this small study, MP2 status and a DNA damage sensing pathway but not the PARPi7 or other repair pathways show promise as predictive biomarkers for immune checkpoint inhibition therapy in breast cancer.

Citation Format: Yau C, Wolf D, Brown-Swigart L, Hirst G, Sanil A, Singhrao R, I-SPY 2 TRIAL Investigators, Asare S, DeMichele A, Berry D, Esserman L, van 't Veer L, Nanda R, Liu M, Yee D. Analysis of DNA repair deficiency biomarkers as predictors of response to the PD1 inhibitor pembrolizumab: Results from the neoadjuvant I-SPY 2 trial for stage II-III high-risk breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD6-14.

High-throughput screen of natural product extracts in a yeast model of polyglutamine proteotoxicity

Proteins with expanded polyglutamine (polyQ) segments cause a number of fatal neurodegenerative disorders, including Huntington's disease (HD). Previous high-throughput screens in cellular and biochemical models of HD have revealed compounds that mitigate polyQ aggregation and proteotoxicity, providing insight into the mechanisms of disease and leads for potential therapeutics. However, the structural diversity of natural products has not yet been fully mobilized toward these goals. Here, we have screened a collection of ~11 000 natural product extracts for the ability to recover the slow growth of ΔProQ103-expressing yeast cells in 384-well plates (Z' ~ 0.7, CV ~ 8%). This screen identified actinomycin D as a strong inhibitor of polyQ aggregation and proteotoxicity at nanomolar concentrations (~50-500 ng/mL). We found that a low dose of actinomycin D increased the levels of the heat-shock proteins Hsp104, Hsp70 and Hsp26 and enhanced binding of Hsp70 to the polyQ in yeast. Actinomycin also suppressed aggregation of polyQ in mammalian cells, suggesting a conserved mechanism. These results establish natural products as a rich source of compounds with interesting mechanisms of action against polyQ disorders.

Cyclic Stress Relaxation (Csr) of Filled Rubber and Rubber Components

Under repeated stressing it is well known that rubber materials exhibit cyclic stress relaxation (CSR). Previous work has shown that the amount of relaxation observed from cycle to cycle is significantly greater than that expected from static relaxation measurements. The reduction in the stress attained on the second and successive loading cycles as compared to the stress attained on the first cycle in a stress strain cyclic test of fixed amplitude has been measured for elastomer test pieces and engineering components. It is seen that the peak force, under cyclic testing to a specific maximum displacement, plotted against the number of cycles on logarithmic scales produces a straight line graph, whose slope correlates to the rate of cyclic stress relaxation per decade. The rate of cyclic stress relaxation was found to increase with displacement amplitude in all modes of deformation. Plotting the rate of stress relaxation per decade against the maximum average strain energy attained in the cycle reduces the data measured in different deformation modes for both simple test pieces and components to a single curve. This approach allows the cyclic stress relaxation in a real component to be predicted from simple laboratory tests.