key: cord-0318749-veekksrb authors: Kolpashnikova, K. title: Ageing and Dementia: Age-Period-Cohort Effects of Policy Intervention in England, 2006-2016 date: 2021-03-13 journal: nan DOI: 10.1101/2021.03.13.21253508 sha: e44dc3501af5e42a72ff125cc88d869828077159 doc_id: 318749 cord_uid: veekksrb Background: Dementia is one of the most important challenges of our time. According to the Dementia Statistics Hub, only about 66% of all UK residents with dementia were diagnosed in 2017-2018. Yet, there are reservations about the early diagnosis of dementia-related diseases. As a result, the UK National Screening Committee does not recommend systematic population screening of dementia. Methods: This study added additional evidence of the effectiveness of the National Dementia Strategy and increased numbers of diagnosis of dementia on the younger cohorts of the elderly, using the intrinsic estimator age-period-cohort models and the English Longitudinal Study of Ageing data. Results: Age effects show that screening and diagnosis increases in volume only among those aged 75 and above, suggesting that many of the younger elderly were not diagnosed. Period effects show that although there was an initial increase due to new policy implementation, the trend stalled in later years, indicating that the increase might not have been even across the period when controlled for age and cohort. The study also shows that cohort effects indicate lower prevalence in younger cohorts controlled for age and period. Conclusions: Although more research in diverse contexts is warranted, this study cautions against the abandonment of timely diagnosis and increased screening and shows some effectiveness of prevention strategies on the national level. According to Dementia Statistics Hub, one in three people with dementia are left undiagnosed in the UK [1] . Between 2009 and 2015, the UK put tremendous efforts in addressing dementia in domestic health policy, including increasing diagnosis rates, promoting awareness and prevention, and changing treatment strategies [2] . This study attempts to contribute to the previous research and evaluate UK health policy effects on dementia diagnosis using the age-period-cohort analysis. It is particularly important to evaluate the effects of the national policy and strategy change, given the urge to evaluate its adequacy was expressed in recent work [3, 4] . The National Dementia Strategy (NDS) was launched in February 2009 to improve awareness about the illness, encourage an increase in diagnosis, prevention, and the quality of care for people diagnosed with dementia-related diseases. In 2012, NDS was superseded by Dementia Challenge, which was then updated to Dementia 2020 Challenge in 2015. Among other changes with the UK-wide dementia policy, more people with mild dementia were prescribed acetylcholinesterase inhibitors, whereas antipsychotic prescriptions continued to decrease [2] . K Donegan, N Fox, N Black, G Livingston, S Banerjee and A Burns [2] report that the prescription of antidementia medication doubled in percentage in between 2005 and 2015 and reached 36.3%, whereas the antipsychotic drug prescription halved from 22.1% to 11.4%. Research shows that acetylcholinesterase inhibitors may slow down the cognitive decline in patients with Alzheimer's disease, though more research is warranted [5, 6] . Although the present paper does not aim to call for the reversal of the current screening mandate in the UK, since the harmful effects of the early diagnosis need to be addressed and clear ethical and procedural measures outlined in the communication with the patients and caregivers [4] , it aims to provide new investigative evidence whether any changes were . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint As the age effects are expected to follow the national recommendations on screening, this study is mostly interested in the analysis of period and cohort effects. The invariable period effects would suggest that there were no screening and diagnosis increase in the period, controlled for age and cohort, which we know is not factual in the case of the diagnosis of dementia in the analysed period [1] . On the one hand, the invariant cohort effects would confirm the assumption that prevention strategies, as well as the concurrent changes in treatment strategies, had no effect on the younger cohorts of the elderly. On the other hand, changes in the cohort trends might indicate some evidence of the opposite. The English Longitudinal Study of Ageing (ELSA) is used for the analysis [7] and was is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 13, 2021. ; https://doi.org/10.1101/2021.03.13.21253508 doi: medRxiv preprint The dependent variable is measured by whether the diagnoses of dementia-related diseases, including Alzheimer's disease, were reported at the surveyed wave. The outcome is a dummy variable, 1 for 'yes' and 0 for 'no'. Table 1 summarizes the dementia-related disease prevalence rates by age group and cohorts. It shows that the prevalence rate increases with age and that it is higher in older cohorts, as expected. The table also shows that the increased diagnosis in the pre-2015 period reported more cases of dementia for younger elderly (in between 65 and 74) and among those who were above 80 years of age. The analysis is based on the five-year intervals of the categories of age, period, and cohort, which are usually used in the analysis of APC effects [8] [9] [10] . The intervals of five years were is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 13, 2021. ; https://doi.org/10.1101/2021.03.13.21253508 doi: medRxiv preprint This paper's models employ the intrinsic estimator (IE) to disentangle age-period-cohort effects in dementia-related diseases [8, 11] . The IE modelling in age-period-cohort analysis remains the most appropriate way to analyse the effects without having to impose constraints on either age, period, or cohort categories [9, 10, 12] . Some critiques of the method exist. For instance, L Luo [13] showed that IE models would not work in all situations, using simulations. However, later, RK Masters, DA Powers, RA Hummer, A Beck, S-F Lin and BK Finch [12] showed that the situations where IE models will not work are very unlikely to happen in the real world and reclaimed the confidence in IE models in age-period-cohort analysis. In public health research, Bell's HAPC models, developed in A Bell [14] , are used more commonly than the IE models. However, the HAPC models require strong assumptions regarding (usually) period effects [15] . Considering that period effects are expected to vary between 2006 and 2017 in England's dementia prevalence trends, the use of IE models is preferred in the present paper. Table 2 presents the results from the IE models on dementia-related diseases' prevalence. Most of the age-period-cohort effects are significant in the model. Model 1 shows that the prevalence increases with age and period and decreases with a cohort change, except for the cohort born during WWII and the oldest cohort. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint Standard errors in parentheses. + p < 0.10, * p < 0.05, ** p < 0.01, *** p < 0.001 Age effects based on the IE model in Table 3 are presented in Figure 1 . The trends reveal that the diagnosis (preceded by screening) mostly happen among people of aged 75 and above. This indicates that even during the analysed period since the start of the NDS with a policy mandate for increased testing of dementia, those aged 74 and below were rarely screened and diagnosed with dementia. The descriptive findings in Table 1 confirm this result for people of age 69 and below. For those between 70 and 74, the prevalence rate doubled between the first and the second period and reverted to the first period's levels in the third period. These results suggest that very few younger elderly are diagnosed in a timely manner, even after the NDS, reflecting the current recommendations of the UK National Screening Committee. The steep increase for those aged 75 and above on the age effects confirms that many of these cases might remain undetected earlier if we assume that the prevalence increases gradually rather than exponentially over age groups. These results of the age effects are expected and are according to the national guidelines on the screening and diagnosis of dementia-related diseases. . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 13, 2021. ; https://doi.org/10.1101/2021.03.13.21253508 doi: medRxiv preprint Overall, the period effects confirm that the call for increased diagnosis in dementia was delivered since the implementation of the NDS but stalled in recent years. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 13, 2021. ; https://doi.org/10.1101/2021.03.13.21253508 doi: medRxiv preprint The cohort effects in this study can potentially show the effectiveness of the dementia risk prevention policy if a decreasing trend in prevalence is detected in earlier cohorts, net of age and period effects. The trends show that the risk prevention activities, treatment strategy changes, as well as changes in the lifestyle of the younger cohorts not related to the policy implementation might have positively affected the younger cohorts, particularly those born between 1950-1954. However, striking differences in prevalence can be confirmed between the younger cohort in the survey and those who are ten years older than them, which gives us a bit of optimism in terms of the effects of the risk prevention measures, although the association might be explained by other factors unrelated to the policy implementation as well. More extended observation is warranted to be able to say anything definitively. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 13, 2021. ; https://doi.org/10.1101/2021.03.13.21253508 doi: medRxiv preprint screening recommendations installed on the national level. The period effects reveal a substantial increase in diagnosis following the implementation of the National Dementia Strategy and consequent stall in the trend in the later years. The cohort effects show some improvement in younger cohorts, suggesting the effectiveness of preventive policy or generational changes in lifestyles. However, the evidence presented in this study is not conclusive because of the limited data, and more research is warranted, particularly using a range of data from diverse contexts. The way to do this is to analyse the APC effects across different contexts, depending on their screening strategies and selected preventive measures, including in European, North American, Asian, and other countries. One limitation of this study is that the prevalence of early detection of dementia-related diseases in the younger cohorts can also be related to other cohort-related changes: lifestyles and decreases in alcohol consumption and smoking, among other things. Future research could focus on the effects of preventive measures and increased diagnosis over longer periods of time, particularly with the focus on mild cognitive impairment screening over time. The study is supported by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant (892101). is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted March 13, 2021. ; https://doi.org/10.1101/2021.03.13.21253508 doi: medRxiv preprint Trends in diagnosis and treatment for people with dementia in the UK from 2005 to 2015: a longitudinal retrospective cohort study. The Lancet Public Health Against the stream: early diagnosis of dementia, is it so desirable? BJPsych bulletin Attitudes towards prediction and early diagnosis of late-onset dementia: a comparison of tested persons and family caregivers Acetylcholinesterase inhibitors in Alzheimer's disease influence Zinc and Copper homeostasis Acetylcholinesterase inhibitors for the treatment of dementia in Alzheimer's disease: do we need new inhibitors? 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