Challenges and way forward for implementation of sugar taxation in the Middle East and North Africa (MENA).

BACKGROUND: Over consumption of added sugar beyond the World Health Organization (WHO) recommended level of 10% of daily energy intake has well-established negative health consequences including oral diseases. However, the average consumption of added sugar in the Middle East and North Africa region (MENA-World Bank's regional classification) is 70% higher than the WHO recommended level. Imposing taxes on added sugar has been proposed by the WHO to decrease its consumption. Yet, only 21.6% of the total MENA population are covered by taxation policies targeting added sugar. CHALLENGES: Well-recognized challenges for the implementation of sugar taxation in MENA include the tactics used by the food and beverage industry to block these type of policies. However, there are also other unfamiliar hurdles specific to MENA. Historically, there have been incidents of protest and riots partially sparked by increased price of basic commodities, including sugar, in MENA countries. This may affect the readiness of policy makers in the region to impose added sugar taxes. In addition, there are also cultural, lifestyle and consumption behavioural barriers to implementing added sugar taxation. Ultra-processed foods and sugar-sweetened-beverages (SSBs) rich in added sugar are perceived by many in MENA as essential treats regardless of their health risks. Furthermore, some countries even provide subsidies for added sugar. Also, (oral) healthcare providers generally do not engage in policy advocacy mainly due to limited training on health policy. WAYS FORWARD: Here, we discuss these challenges and suggest some ways forward such as (1) support from a health-oriented political leadership, (2) raising public awareness about the health risks of over consumption of sugar, (3) transparency during the policy-cycle development process, (4) providing a free and safe environment for a community dialogue around the proposed policy, (5) training of (oral) healthcare professionals on science communication and policy advocacy in local lay language/dialect, ideally evidence informed from local/regional studies, (6) selecting the appropriate political window of opportunity to introduce a sugar tax policy, and (7) clear and strict conflict of interest regulations to limit the influence of commercial players on health policy.

Sugar-sweetened beverage consumption and periodontitis among adults: A population-based cross-sectional study.

AIM: Investigating the association between sugar-sweetened beverages (SSBs) and periodontitis and whether the awareness of diabetes modifies this relationship. MATERIALS AND METHODS: Cross-sectional analysis was conducted using the National Health and Nutrition Examination Survey (NHANES III) data involving US adults aged 30-50. Periodontitis was classified according to the Centers for Disease Control and Prevention and American Academy of Periodontology (CDC-AAP), and SSB consumption as dichotomous (<5 or ≥5, <7 or ≥7 and <14 or ≥14 times/week), ordinal and continuous variables. Confounders included family income poverty ratio, education, race/ethnicity, sex, age, food energy intake, smoking and alcohol. Odds ratios (ORs) were obtained by logistic regressions using inverse probability weighting. Effect modification analysis was performed considering self-reported diabetes. RESULTS: Among 4473 cases analysed, 198 self-reported diabetes. SSBs were associated with periodontitis when individuals consumed ≥5 (OR 1.64; 95% confidence interval [CI] = 1.30-2.06), ≥7 (OR 1.92; 95% CI = 1.50-2.46) and ≥14 (OR 2.19; 95% CI = 1.50-3.18) times/week. The combined effect of consuming SSBs (≥5 and ≥14 times/week) and self-reported diabetes had less impact than the cumulative effect. CONCLUSIONS: SSB consumption was associated with higher odds of periodontitis, and the estimates were reduced among those with awareness of diabetes.

Incidence, mortality and survival rates of lip, oral cavity and salivary glands cancers in Singapore: A half-century time trend analysis (1968-2017).

OBJECTIVES: To examine trends in incidence and mortality and evaluate overall survival (OS) of oral cancer in Singapore between 1968 and 2017. METHODS: All diagnosed oral cancers by anatomical sites and population size were extracted from the Singapore Cancer Registry and the Department of Statistics Singapore. The trend of age-standardized incidence rate (ASIR) and mortality rate (ASMR) (per 100 000 person-years) of the lip, oral cavity and salivary gland cancers were evaluated by Prais-Winsten regressions for each ethnicity and gender. Kaplan-Meier curves were performed to evaluate the OS by anatomical sites in each age group by ethnicity and sex. RESULTS: Overall, 49, 3494 and 1066 people were diagnosed, and 28, 2310 and 476 died from lip, oral cavity and salivary gland cancers, respectively. The oral cavity cancer ASIR and ASMR reduced from 3.07 (1968-1972) to 2.01(2008-2012) and from 2.06 (1978-1982) to 1.21 (2013-2017) per 100 000 person-years, respectively, with both highest in Indians throughout the whole period. Male:Female ratio ranged from 3.43 (1973-1977) to 1.75 (2013-2017) and from 3.41 (1978-1982) to 2.40 (2013-2017) for ASIR and ASMR, respectively. However, both salivary gland cancer ASIR and ASMR increased from 0.50 (1968-1972) to 0.80 (2008-2012) and from 0.18 (1968-1982) to 0.42 (1988-1992) per 100 000 person-years, respectively, with both higher in males since 1993. Oral cavity cancer ASIR decreased for males aged ≥60, and Indian females ≥25, but increased among Chinese females aged ≥60. Oral cavity cancer ASMR decreased among Chinese aged 25-59, and among Malay males and Indian females. Salivary gland cancer ASIR increased among Chinese males aged ≥60 and Malay males aged 25-59; while ASMR increased among Chinese males aged ≥60. The median OS for oral cavity, lip and salivary gland cancers were 3.0, 9.3 and 18.1 years, respectively, with females surviving longer than males. CONCLUSIONS: Singapore has experienced a decline in the incidence and mortality of lip, oral cancer, an increase in in the incidence and mortality of salivary gland cancer, with an increase in the median overall survival rate. Monitoring the magnitude of oral cancer burden and the demographic, and temporal variations is necessary for tailoring health planning and setting priorities for future clinical care and research.

Chewing Disability Is Associated With Cognitive Impairment Among Older Adults: A Population-Based Cohort Study.

BACKGROUND: Chewing disability is associated with impaired quality of life, potentially leading to depression, and cognitive impairment. Although the chewing-ability-cognition relationship has been explored, examining whether depression mediates this relationship remains unclear. We investigated the association between chewing disability and cognitive impairment development and a potential mediation via depression among older persons. METHODS: Older persons without cognitive impairment at baseline (n = 973) from the 3 waves of the Panel on Health and Ageing of Singaporean Elderly were investigated. The outcome was incident cognitive impairment by the end of the study, while the exposure was chewing disability over the study period. Time-varying depression was the mediator. Time-fixed confounders included sex, ethnicity, education, marital status, living arrangement, and housing type, and time-varying confounders included age, smoking, cardiovascular diseases, diabetes, number of teeth, and denture wearing. We used marginal structural modeling to evaluate the effect of chewing disability on cognitive impairment development. RESULTS: After 6 years, 11% developed cognitive impairment, and chewing disability was reported by 33%. Chewing disability was associated with higher odds of developing cognitive impairment (OR 1.43, 95% CI: 1.09, 1.87), of which 85.3% was explained by the controlled direct effect of chewing disability, whereas the remaining 14.7% could be eliminated if there was no depression. CONCLUSIONS: Our findings indicate an association between chewing disability and cognitive impairment, while the role of depression could not be fully elucidated. Oral health should be incorporated as part of older persons' care for its potential to assess the risk for other systemic conditions.

Do dental anxiety and satisfaction with dental professionals modify the association between affordability and dental service use? A population-based longitudinal study of Australian adults.

OBJECTIVES: This study aimed to assess the association between affordability in terms of difficulty paying dental bills in Australian dollars and dental service use in the presence of sociodemographic confounders, and to assess the role of dental anxiety and satisfaction with dental professionals as mediators. The second aim was to investigate how dental anxiety and satisfaction with dental professionals modify the association between affordability and use of dental services in Australian adults. METHODS: Longitudinal data from the Australian National Study of Adult Oral Health (2004-06 and 2017-18) was used. Poisson regression and path analysis were conducted to determine the association between affordability and frequency of use of dental services. Effect measure modification (EMM) analysis was performed by stratification of dental anxiety and satisfaction with dental professionals. RESULTS: The study included 1698 Australian adults and identified that the prevalence of low frequency of dental visits was 20% more for those who had difficulty paying dental bills. Adults with dental anxiety (prevalence ratio [PR] = 1.14) and those who were dissatisfied with dental professionals (PR = 1.17) had a higher prevalence of low frequency of dental visits in the presence of difficulty paying dental bills. This indicated that dental anxiety and dissatisfaction with dental professionals were effect modifiers on this pathway. CONCLUSIONS: Adults who experience dental anxiety and dissatisfaction with dental professionals are more likely to avoid dental visits when faced with difficulty paying dental bills. However, it is important to note that these associations do not necessarily imply a causal relationship.

Structural Relationships between Asthma and Dental Caries in Children: A Birth Cohort Study in Southern Brazil.

INTRODUCTION: There is an inconclusive causal association between asthma symptoms and dental caries in the primary dentition. This study aimed to investigate, using SEM (structural equation modeling), a possible causal relation between asthma and dental caries in the primary dentition. METHODS: Using data from the 2004 Pelotas Birth Cohort Study, a sub-sample of 1,303 individuals was selected. Dental caries was clinically evaluated at 5 years old based on decayed, missing, and filled tooth (dmft) index criteria. Asthma-related symptoms (wheezing and shortness of breath) at 1- and 4-year-olds composed a latent variable and were the main exposures to caries occurrence. SEM was used to identify possible direct, indirect, and mediated effects of asthma in primary dentition dental caries. RESULTS: The general prevalence of caries at age 5 was 1.95 (SD: 3.56). When comparing the dmft values for children with asthma symptoms and those without, they presented similar values in both periods where asthma symptoms were evaluated (1- and 4-year-old). SEM analysis showed that asthma was neither directly nor indirectly related to dental caries. CONCLUSION: Asthma, using a latent variable constructed based on asthma symptoms, showed no causal effect on dental caries occurrence in the primary dentition.

Assessing the surveillance use of 2018 EFP/AAP classification of periodontitis: A validation study and clustering analysis.

BACKGROUND: The performance of the 2018 European Federation of Periodontology/American Academy of Periodontology (EFP/AAP) classification of periodontitis for epidemiology surveillance purposes remains to be investigated. This study assessed the surveillance use of the 2018 EFP/AAP classification and its agreement with the unsupervised clustering method compared with the 2012 Centers for Disease Control and Prevention(CDC)/AAP case definition. METHODS: Participants (n = 9424) in the National Health and Nutrition Examination Survey (NHANES) were staged by the 2018 EFP/AAP classification and classified into subgroups via k-medoids clustering. Concordance levels between periodontitis definitions and the clustering method were evaluated through the multiclass area under the receiver operating characteristic curve (multiclass AUC) among "periodontitis cases" and the general population, respectively. The multiclass AUC of the 2012 CDC/AAP definition versus clustering was used as a reference. The associations of periodontitis with chronic diseases were estimated using multivariable logistic regression. RESULTS: All the participants were identified as "periodontitis cases" by the 2018 EFP/AAP classification, and the prevalence of stage III-IV was 30%. The optimal numbers of clusters were three and four. The 2012 CDC/AAP definition versus clustering yielded a multiclass AUC of 0.82 and 0.85 among the general population and "periodontitis cases," respectively. The multiclass AUC of the 2018 EFP/AAP classification versus clustering was 0.77 and 0.78 for different target populations. Similar patterns prevailed in associations with chronic diseases between the 2018 EFP/AAP classification and clustering. CONCLUSIONS: The validity of the 2018 EFP/AAP classification was verified by the unsupervised clustering method, which performed better in distinguishing "periodontitis cases" than classifying the general population. For surveillance purposes, the 2012 CDC/AAP definition showed a higher agreement level with the clustering method than the 2018 EFP/AAP classification.

Australians support for policy initiatives addressing unhealthy diet: a population-based study.

To inform public health policy implementation in Australia, our study investigated the level of public support for six policy initiatives addressing unhealthy diet. The policy initiatives included taxing soft drinks and energy drinks, taxing less healthy food and beverage purchases, zoning to restrict the supply of junk foods near schools, prohibiting advertising and promotion of less healthy food and beverages to children under the age of 16 and restricting sugar-sweetened beverages from vending machines in schools, and public places. Data from a cross-sectional population-based study for 4040 Australians aged 15+ years, were analysed. A high overall support across all policy initiatives was observed. Nearly three-quarter of public support was observed for policy initiatives targeting children (zoning to restrict the supply of junk food near schools, prohibiting advertising and promotion of less healthy food and beverages to children under the age of 16 and restricting sugars-sweetened beverages from vending machines in schools), and half of Australians supported policy initiatives of taxing soft drinks and energy drinks and taxing less healthy food and beverage purchases. Australian women and those with tertiary level of education were more likely to support public health initiatives targeting children and all policy initiatives respectively. Interestingly, young adults expressed low level of support for all policy initiatives. The study demonstrated considerable public support for policy initiatives focussed on protecting children from unhealthy diet in Australia. Framing, designing and implementing policies targeting children is potentially a good starting point for policymakers to create a health promoting food environment.

Longitudinal association between periodontal condition and glycaemic status in middle-aged adults: A cross-lagged panel analysis.

AIM: To investigate the existence of a bidirectional temporal relationship between periodontal condition and glycaemic status. MATERIALS AND METHODS: This longitudinal study included 2198 participants with mean age 43.4 ± 7.7 years, who underwent dental examinations in Yokohama, Japan, at two time points, 2003-2004 and 2008-2009, at an interval of 5 years. Periodontal condition was assessed by the mean value of probing pocket depth (PPD) and clinical attachment level (CAL). Glycaemic status was assessed by fasting glucose and glycated haemoglobin (HbA1c). RESULTS: The cross-lagged panel models showed the effect of HbA1c at baseline on mean PPD at follow-up (ß = 0.044, p = .039). There was a marginal effect of fasting glucose on the mean PPD (ß = 0.037, p = .059). It was similar to the effect of fasting glucose or HbAlc on mean CAL. However, in the opposite direction, no effect of mean PPD or CAL at baseline on fasting glucose or HbAlc at follow-up was identified. CONCLUSIONS: This study demonstrated a unidirectional relationship between glycaemic status and periodontal condition. The study population, however, had mostly mild periodontitis. Future studies are needed to investigate the effect of periodontal condition on glycaemic status in patients with severe periodontitis.

Education-related inequalities in oral health among older adults: Comparing Singapore and Japan.

OBJECTIVES: Oral health inequalities exist worldwide, and cross-country comparisons can provide valuable insights into country-level characteristics contributing to such inequalities. However, comparative studies in Asian countries are limited. This study examined the magnitude of education-related oral health inequalities in older adults in Singapore and Japan. METHODS: Longitudinal data for older adults, aged ≥65 years, from the Panel on Health and Ageing of Singaporean Elderly (PHASE; 2009, 2011-2012, and 2015) and Japan Gerontological Evaluation Study (JAGES; 2010, 2013, and 2016) were used. Dependent variables were being edentate and having a minimal functional dentition (MFD; i.e. ≥20 teeth). The absolute and relative inequalities were calculated using the slope index of inequality (SII) and relative index of inequality (RII) for educational level [low (<6 years); middle (6-12 years); high (>12 years)] in each country. RESULTS: A total of 1032 PHASE participants and 35 717 JAGES participants were included. At baseline among PHASE participants, 35.9% were edentate and 24.4% had MFD, while among JAGES participants, 8.5% were edentate and 42.4% had MFD. The prevalence of low, middle and high educational levels for PHASE was 76.5%, 18.0% and 5.5%, and for JAGES were 0.9%, 78.1% and 19.7%, respectively. Older adults in Japan had lower education-related inequalities for being edentate [for both SII (-0.53, 95% CI = -0.55 to -0.50) and RII (0.40, 95% CI = 0.33-0.48)] and for not having MFD for both SII (-0.24, 95% CI = -0.27 to -0.20) and RII (0.83, 95% CI = 0.79-0.87) compared to Singapore. CONCLUSIONS: Education-related inequalities for being edentate and not having MFD were higher among older adults in Singapore compared to Japan.

Time trend and Age-Period-Cohort analysis of potentially HPV-related oral and pharyngeal cancer incidence in Singapore between 1968 and 2017.

OBJECTIVES: To examine trends and age-period-cohort effects (APC) on oral and pharyngeal cancers incidence in Singapore between 1968 and 2017 by human papillomavirus (HPV) status. METHODS: All diagnosed oral and pharyngeal cancers and population size were extracted from the Singapore Cancer Registry and the Department of Statistics Singapore, respectively. Anatomical subsites were used as a proxy for HPV infection. Prais-Winsten regression assessed trends of age-standardised incidence rate (ASIR) (per 100,000 person-years); Poisson regression assessed APC effects on HPV-related and HPV-unrelated cancers. RESULTS: Over 50 years, 1,618 HPV-related and 2,977 HPV-unrelated oral and pharyngeal cancers were diagnosed, with the highest ASIR in Indians (6.93), followed by Chinese (2.81), and Malays (1.81). Overall, ASIR HPV-related cancers were stable while HPV-unrelated cancers decreased. The male-female ASIR ratio reduced from 5.82 (1968-1977) to 4.0 (2008-2017) for HPV-related cancers, and from 2.58 (1968-1977) to 1.52 (2008-2017) for HPV-unrelated cancers. HPV-unrelated ASIR in males decreased, but in females only among Indians. HPV-related ASIR decreased only among Indian females. The cohort born between 1983 and 1992 had the lowest incidence of HPV-related cancers in males but the highest in HPV-unrelated cancers. Period effect mainly contributed to HPV-related cancer among males with increased incidence after 1997. Overall, the age effect was more pronounced in males. CONCLUSIONS: HPV-related cancers accounted for 1/3 of oral and pharyngeal cancers. A significant decline was observed only for HPV-unrelated cancers. The cohort effect was mainly attributed to HPV-unrelated cancer incidence, while the period effect largely contributed to HPV-related cancer incidence, but only among males.

Chronic oral diseases burden: The confluence of caries and periodontitis throughout life.

AIM: To investigate the confluence of caries and periodontitis indicators from adolescence to elderhood among Americans. MATERIALS AND METHODS: This cross-sectional study explored the grouping among a set of caries and periodontitis indicators (the proportion of sites with bleeding on probing, moderate probing pocket depth [PPD, 4-5 mm], severe PPD [≥6 mm], moderate clinical attachment level [CAL, 3-4 mm], severe CAL [≥5 mm], number of teeth with furcation involvement, number of decayed teeth, number of teeth with pulp involvement, and the number of missing teeth) in 14,421 Americans from the NHANES III study. Exploratory factorial analysis was used to determine the constructs between those indicators (factorial loading ≥0.3). These analyses were stratified by age and confirmed with a confirmatory factorial analysis. We also performed a sensitivity analysis using the NHANES 2011-2014. RESULTS: Two constructs were extracted. The first, Chronic Oral Diseases Burden, grouped caries indicators with moderate PPD and moderate CAL for the youngest subjects (13-39 years old), while for the subjects over 50 years, the Chronic Oral Disease Burden grouped caries indicators with severe CAL and PPD and furcation involvement. The second construct, Periodontal Destruction, grouped only periodontitis indicators. CONCLUSIONS: Caries and periodontitis indicators grouped consistently across the different age ranges in lapse times of 25 years.

Investigating the causal effect of cognition on the self-reported loss of functional dentition using marginal structural models: The Panel on Health and Ageing of Singaporean Elderly study.

AIM: To assess the effect of cognition on the loss of functional dentition. MATERIALS AND METHODS: We used data from the three waves of the Panel on Health and Ageing of Singaporean Elderly study (n = 4990 at baseline, 774 complete cases analysed) over 6 years (2009-2015). The outcome was the loss of functional dentition (<21 teeth). The exposure was cognitive impairment, while baseline confounders included age, sex, education, and ethnicity. Time-varying confounders included income, living arrangements, smoking, diabetes, depressive symptoms, cardiovascular disease, and body mass index. We used marginal structural mean models with inverse probability treatment weighted. RESULTS: The mean age of the participants was 70.2 years at baseline. The proportion of participants with loss of functional dentition increased from 74.6% to 89.9% over 6 years. Women, ethnic Chinese, less educated, smokers, people with diabetes, and individuals with depression had a higher proportion of loss of functional dentition than their counterparts. Loss of functional dentition was 1.8 times higher (odds ratio 1.80; 95% confidence interval 0.88-3.69) among those with cognitive impairment after taking well-known confounders into account. CONCLUSIONS: After accounting for the time-varying exposure and confounding evidence, the association between cognition and functional dentition among the elderly in Singapore remains uncertain.

Two decades of socioeconomic inequalities in the prevalence of untreated dental caries in early childhood: Results from three birth cohorts in southern Brazil.

OBJECTIVES: To estimate the socioeconomic disparities in untreated dental caries in early childhood according to socioeconomic characteristics in three birth cohorts in Southern Brazil. METHODS: The socioeconomic data to this study were collected at the 48-month follow-up and oral health studies of 1993, 2004 and 2015 Pelotas birth cohort studies. The outcome was untreated dental caries in children aged 6 (1993 cohort), 5 (2004 cohort) and 4 years (2015 cohort), dichotomized into absence/presence. Analyses were stratified by maternal skin colour/race, maternal education and family income. For statistical purposes, the prevalence difference, relative risk and absolute and relative indices of health inequality (Slope Index of Inequality-SII and Concentration Index-CIX) were used. RESULTS: The prevalence of untreated dental caries in primary dentition was 63.4%, 45.5% and 15.6%, in 1993, 2004 and 2015 cohorts, respectively. The prevalence of untreated dental caries was concentrated in the poorest quintile and lower maternal education group in both absolute (SII) and relative (CIX) measures of inequality, being characterized as a pro-poor event. A higher risk of untreated caries was found in the poorest quintile of family income compared with the richest quintile in the 1993 cohort (RR 1.44 [95% CI 1.05; 1.98]). That risk was higher considering the 2004 Cohort (RR 1.78 [95% CI 1.42; 2.23]) and 2015 cohort (RR 4.20 [95% CI 2.97; 5.94]) data. CONCLUSIONS: Over the course of two decades, a higher prevalence of untreated dental caries is concentrated among the most socioeconomically deprived children.

Periodontitis Is Associated with Consumption of Processed and Ultra-Processed Foods: Findings from a Population-Based Study.

The association between periodontitis and lifestyle factors has been widely investigated. However, an association between periodontitis and dietary patterns has not been explored. Therefore, this study investigated the association between periodontitis and food consumption among a Southern Brazil population. Data from the 1982 Pelotas Birth Cohort were used (n = 537). The exposure, periodontitis, was clinically measured and classified using the AAP/CDC system, then two latent variables were defined: 'initial' and 'moderate/severe' periodontitis. The consumption of in natura, processed, and ultra-processed foods (NOVA classification) was the outcome and measured in calories using the food frequency questionnaire (FFQ). Confounders were sex, maternal education, smoking status, xerostomia, and halitosis. Data were analyzed by structural equation modeling. 'Initial' periodontitis was associated with a higher consumption of in natura food (standardized coefficient (SC) 0.102; p-value = 0.040), versus processed (SC 0.078; p-value = 0.129) and ultra-processed (SC 0.043; p-value = 0.400) foods. 'Moderate/severe' periodontitis was associated with higher consumption of ultra-processed foods (SC 0.108; p-value = 0.024), versus processed (SC 0.093; p-value = 0.053) and in natura (SC 0.014; p-value = 0.762) foods. 'Moderate/severe' periodontitis appears to be associated with the consumption of processed and ultra-processed foods.

Who to Be Treated: Nomogram Using Self-Reported Periodontal Screening Instrument among English-Speaking Adults in Multi-Ethnic Singapore.

Periodontal disease is a major public health problem. This study aimed to develop a nomogram using a self-reported periodontitis screening instrument in predicting severe periodontitis (SP), defined by the World Workshop on Classification of Periodontal and Peri-Implant Diseases and Conditions, and evaluate its utility in clinical setting. An Akaike information criterion selected multivariable model was developed to predict SP using a self-reported questionnaire, with a nomogram developed based on its regression coefficients. Discriminatory capability was evaluated by Receiver-operating characteristic curve. Ability to predict SP of individual patients was evaluated with bootstrapping. Decision curve analysis (DCA) was performed to evaluate its potential clinical utility by evaluating clinical net benefit at different thresholds. 58.1% of 155 participants were classified with SP. Older males without tertiary education, with 'loose teeth', 'bone loss' and 'mouth rinse use' had higher SP risk. The nomogram showed excellent discriminatory capability with Area under Curve of 0.83 (95% CI = (0.76, 0.89)), good calibration (intercept = 0.026) and slight overestimation of high risk and underestimation of low risk (slope = 0.834). DCA showed consistent clinical net benefit across the range of thresholds relative to assumption of 'no patient' or 'all patient' with SP. Our nomogram using a self-reported periodontitis instrument is useful in SP screening in English-speaking Singaporean adults.

Approaches to the problem of nonidentifiability in the age-period-cohort models in the analysis of cancer mortality: a scoping review.

Aiming to detect age, period and cohort effects in cancer mortality, age-period-cohort models (APC) can be applied to distinguish these effects. The main difficulty with adjusting an APC model involving age, period and cohort factors is the linear relationship between them, leading to a condition known as the 'nonidentifiability problem'. Many methods have been developed by statisticians to solve it, but there is not a consensus. All these existing methods, with their advantages and disadvantages, create confusion when choosing which one of them should be implemented. In this context, the present scoping review intends not to show all methods developed to avoid the nonidentifiability problem on APC models but to show which of them are, in fact, applied in the literature, especially in the cancer mortality studies. A search strategy was made to identify evidence on MEDLINE (PubMed), Scopus, EMBASE, Science Direct and Web of Science. A total of 46 papers were analyzed. The main methods found were: Holford's method (n = 14; 30%), ntrinsic estimator (n = 10; 22%), Osmond & Gardner method n = 8; 17%), Carstensen (n = 6;13%), Bayesian approach (n = 6;13%) and others (n = 2; 5%). Even with their limitations, all methods have beneficial applications. However, the decision to use one or another method seemed to be more related to an observed geographic pattern.