key: cord-0329551-b0bn6ncp authors: Stafford, M.; Knight, H.; Hughes, J.; Alarilla, A.; Mondor, L.; Pefoyo Kone, A.; Wodchis, W.; Deeny, S. R. title: Associations between multiple long-term conditions and mortality in diverse ethnic groups date: 2022-01-14 journal: nan DOI: 10.1101/2022.01.13.22268828 sha: cd36362cf72cd5aab268baaf52eb974010ba2e27 doc_id: 329551 cord_uid: b0bn6ncp Background Multiple conditions are more prevalent in some minoritised ethnic groups and are associated with higher mortality rate but studies examining differential mortality once conditions are established is US-based. Our study tested whether the association between multiple conditions and mortality varies across ethnic groups in England. Methods and Findings A random sample of primary care patients from Clinical Practice Research Datalink (CPRD) was followed from 1st January 2015 until 31st December 2019. Ethnicity, usually self-ascribed, was obtained from primary care records if present or from hospital records. Cox regression models were used to estimate mortality by number of long-term conditions, ethnicity and their interaction, with adjustment for age and sex for 532,059 patients with complete data. During five years of follow-up, 5.9% of patients died. Each additional long-term condition at baseline was associated with increased mortality. This association differed across ethnic groups. Compared with 50-year-olds of white ethnicity with no conditions, the mortality rate was higher for white 50-year-olds with two conditions (HR 1.77) or four conditions (HR 3.13). Corresponding figures were higher for 50-year-olds of Black Caribbean ethnicity with two conditions (HR=2.22) or four conditions (HR 4.54). The direction of the interaction of number of conditions with ethnicity showed higher mortality associated with long-term conditions in nine out of ten minoritised ethnic groups, attaining statistical significance in four (Pakistani, Black African, Black Caribbean and Black other ethnic groups). Conclusions The raised mortality rate associated with having multiple conditions is greater in minoritised ethnic groups compared with white people. Research is now needed to identify factors that contribute to these inequalities. Within the health care setting, there may be opportunities to target clinical and self-management support for people with multiple conditions from minoritised ethnic groups. The number of people with multiple long-term conditions, or multimorbidity, is rising. Though there is no accepted international definition of multimorbidity(1), recent large-scale studies using electronic health records in the UK estimate 23-27% of people have two or more long-term conditions (2) (3) . Multimorbidity has been consistently associated with poorer outcomes for patients, with risk of death increasing with each additional condition(4) (5) and some studies suggesting that the association may be multiplicative(6), and more pronounced when conditions concern different body systems (complex multimorbidity)(7)(8)(9)(10)(11) though the association between higher risk of mortality and multimorbidity is weaker at older ages (12)(13). Multimorbidity is also associated with higher use of health care (2) and reduced quality of life (14, 15) . Many health and care systems are designed to care for patients with single conditions, but there is growing recognition that if they are to improve outcomes for patients, health care systems must be adapted to address the challenge of multimorbidity (16) (17) . There is an established body of evidence that the prevalence of multimorbidity is socially patterned. Previous studies have demonstrated an association between the prevalence of multiple conditions and socioeconomic disadvantage in households (18) and local areas (2, 3) (19) . The prevalence of multiple conditions is also higher in some minoritised ethnic groups (20) . People from some minoritised ethnic groups are more likely to have experienced discrimination and multiple disadvantage over their life course, leading to an increased risk of experiencing material deprivation, living in deprived areas and an associated higher prevalence of downstream behavioural risk factors including smoking and obesity (20) (21) . Poorer experience of healthcare services has also been reported by some minoritised ethnic groups, and they are less likely than their counterparts in the majority population to report that they are able to manage their own health (22) . . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 14, 2022. ; https://doi.org/10.1101/2022.01.13.22268828 doi: medRxiv preprint Whether minoritised ethnic groups experience disadvantage or discrimination over the course of their lives will differ between countries and over time, and as a result, evidence on mortality risk for minoritised ethnic groups varies. For example while excess deaths in Black populations in the US have remained high for many years (23) , in the UK, the link between ethnic minority status and mortality risk varies by cause of death (24) and migration status (25) . Research in the UK on this topic has been hampered due to lack of ethnicity data on death certificates and historically poor recording of ethnicity in medical records, though the latter has improved markedly in recent years. A previous study in the United States of America found that having multiple chronic conditions resulted in reduced life expectancy but the impact did not differ between African Americans and non-Hispanic white people (26) . Analysis of the Health and Retirement Study, on the other hand, found that Black and Hispanic Americans were more likely to have multisystem multimorbidity and more likely to die during follow-up compared with their White American counterparts (27) . We are not aware that this has been assessed in the UK context, though here studies have investigated ethnic differences in long-term survival for people with a single or index condition of interest. These point to the possibility of ethnic differences in survival across a range of conditions, for example lower two-year survival for Black women in England with breast cancer (28) and higher survival for people in London with unipolar depression from Black Caribbean, Black African, South Asian and Chinese ethnic backgrounds (29) . It is plausible that many of the factors contributing to high prevalence of multiple conditions may also contribute to poorer survival in minoritised ethnic groups once multiple conditions are established. Likewise, the potential for differences across ethnic groups in the association between long-term conditions and mortality may be greater where the organisation of health . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted January 14, 2022. ; https://doi.org/10.1101/2022.01.13.22268828 doi: medRxiv preprint care and the recommended treatments and lifestyle changes are especially complex, as is the case with multiple conditions. The aims of our study were to estimate the mortality risk of having multiple conditions, assess whether this risk is seen for complex multimorbidity, and examine whether the magnitude or direction of these risks varies across ethnic groups, compared with people of white ethnicity living in England. Our sample was drawn from primary care records. Over 95% of the England population are registered with a general practice. A random sample of 600,000 adults (age 18 and over) was drawn from the Clinical Practice Research Datalink (CPRD Aurum (30) ). This research database of anonymised routinely collected primary care records captures diagnoses, symptoms, prescriptions, referrals and tests and includes over 40 million patients (13 million currently registered as of June 2021). CPRD Aurum comprises GP practices using the EMIS Web software (one of four main general practice IT systems in operation) that have agreed to contribute data. Eligible adults were in a CPRD practice on 1 st January 2014 (to ensure records were up to date at least one year before the study start), were alive and still registered at the study start on 1 st January 2015, and were eligible for linkage to Hospital Episode Statistics (HES) and Office for National Statistics mortality data. They were followed until the study end (31 st December 2019) or death if this was earlier and were censored if they left the CPRD practice or the practice stopped providing data to CPRD. The study was approved by the CPRD team (eRAP protocol number 20_000239). . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted January 14, 2022. ; https://doi.org/10.1101/2022.01.13.22268828 doi: medRxiv preprint Survival time was calculated from 1 st January 2015 to death or censoring. The number of long-term conditions was counted at study start. We used a list of 32 physical and mental health conditions (Supplementary Table 1 ) that have previously been associated with higher mortality risk, poorer functioning, and requiring primary care input (2, 3) . This was repeated to calculate number of conditions at the study end or censoring date, which may be fewer than at study start as we allowed for three conditions (anxiety/depression, asthma and cancers) to resolve. Complex multimorbidity was defined as having three or more long-term conditions in three or more different body systems(31) (Supplementary Table 1 ). Ethnic identity, usually self-ascribed, was obtained from SNOMED codes recorded by the GP or, where that was missing or incomplete (29.8%), from linked HES (Hospital Episode Statistics) records. Where multiple values of ethnicity have been recorded, we selected the modal value where this was unique, or the most recent value (32) . Categories from the England 2011 census were used in our analysis but we combined white British, white Irish and other white because these separate categories were not available in HES. The analytical sample included those with complete data on sex, age (n=0 excluded), ethnicity (n= 67524 excluded), or deprivation (n=417 excluded). Excluded patients were younger, more likely to be men, over-represented in less deprived areas, and had fewer conditions (Supplementary Table 2 ). . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted January 14, 2022. ; https://doi.org/10.1101/2022.01.13.22268828 doi: medRxiv preprint The association between survival time and baseline number of long-term conditions was modelled using a multilevel Cox proportion hazards model with adjustment for baseline age (centred at age 50 to aid interpretation), sex and ethnicity. Number of conditions was included as a continuous variable after confirming its association with survival time was linear (Supplementary Table 3 ). Ethnicity by age interactions were included as this improved model fit. A two-level model was used to allow for the clustering of patients within GP practices (model 1). We assessed model 1 for violations of the proportional hazards assumption. The association between sex and mortality hazard was found to depend on follow-up time (p=0.004), with a marginally higher hazard for men after 2.5 years of follow-up. The association between baseline age and mortality hazard also depended on follow-up time (p=0.02), with a marginally higher hazard with advancing age after 2.5 years of follow-up. However, the differences across follow-up time were small. Furthermore, allowing for time-varying estimates for sex and age did not alter the estimates for the main variables of interest (namely, ethnicity and number of long-term conditions) so we elected to present the simpler model without time-varying estimates. To examine whether the association between survival time and long-term conditions varied by ethnicity, we added ethnicity by number of conditions interaction terms (model 2). A likelihood ratio test was used to test the combined statistical significance of these interactions (model 2 vs model 1). We examined two possible factors that could explain survival differences across ethnic groups, if any were observed (model 3). We added number of long-term conditions at end of follow-up. Patterns and rate of long-term condition acquisition vary across ethnic groups (20, 27, 33) (34) . We also added socioeconomic deprivation. There is a well-established relationship between ethnic minority identity and greater socioeconomic deprivation, driven . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 14, 2022. ; https://doi.org/10.1101/2022.01.13.22268828 doi: medRxiv preprint by long-standing structural factors that disadvantage people from minoritised ethnic groups in multiple domains including housing, education and employment. We hypothesised that any ethnic differences in the association between survival time and baseline number of conditions would be smaller in models that included number of long-term conditions at end of follow-up and deprivation. In sensitivity analysis, we repeated model 2 replacing baseline number of conditions with presence or absence of complex multimorbidity. We also looked at the presence of conditions in specific body systems that are leading causes of death (35) and that had sufficient sample size across ethnic groups (endocrine, circulatory, respiratory). Here, significance refers to statistical significance at the 5% level. During the 5-year follow-up period, 5.9% of patients died ( Table 1 ). The majority of patients were of white ethnic background (85.4%) and these were older and over-represented in less deprived areas compared with all other ethnic groups (Supplementary Table 4 ). The unadjusted mean number of long-term conditions at baseline was highest in the white ethnic group (1.23) and lowest in the Chinese ethnic group (0.33). The initial model (model 1) addressed the first objective, to assess whether number of longterm conditions is associated with mortality. This model is based on the assumption that the association between number of conditions and mortality is consistent across ethnic groups. Each additional long-term condition at baseline was associated with increased mortality. For example, the hazard ratio (HR) was 1.80 with two conditions and HR=3.25 with four conditions, compared to the reference group with no conditions at age 50 (example hazard ratios in Table 2 and Supplementary Table 5 for full set of estimates). Statistically significant . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted January 14, 2022. ; https://doi.org/10.1101/2022.01.13.22268828 doi: medRxiv preprint interactions for number of conditions by baseline age shows that the relative difference in mortality for those with more versus no conditions was smaller at older ages. Ethnicity was associated with mortality and this association depended on age. Taking patients of white ethnicity age 50 years at baseline as the reference, the hazard ratio was above 1 indicating a higher relative mortality rate for the Pakistani, Black Caribbean, Black other and mixed ethnic groups. For 70-year olds, the hazard ratio was highest for those of white ethnicity. At all ages, the mortality rate was significantly lower for those of Indian or Chinese ethnicity than for those of white ethnicity. Model 2 summarises analysis addressing the second objective and provides evidence that the association between number of conditions and mortality differed across ethnic groups (likelihood ratio test 0.05