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ObjectiveTo determine whether COVID-19 has a significant impact on adequacy of household income to meet basic needs (primary outcome) and work absence due to sickness (secondary outcome), both at the onset of illness (short term) and subsequently (long term).DesignMultilevel mixed regression analysis of self-reported data from monthly online questionnaires, completed 1 May 2020 to 28 October 2021, adjusting for baseline characteristics including age, sex, socioeconomic status and self-rated health.Setting and participantsParticipants (n=16 910) were UK residents aged 16 years or over participating in a national longitudinal study of COVID-19 (COVIDENCE UK).ResultsIncident COVID-19 was independently associated with increased odds of participants reporting household income as being inadequate to meet their basic needs in the short term (adjusted OR (aOR) 1.39, 95% CI 1.12 to 1.73) though this did not persist in the long term (aOR 1.00, 95% CI 0.86 to 1.16). Exploratory analysis revealed a stronger short-term association among those who reported long COVID, defined as the presence of symptoms lasting more than 4 weeks after disease onset, than those reporting COVID-19 without long COVID (p for trend 0.002). Incident COVID-19 associated with increased odds of reporting sickness absence from work in the long term (aOR 4.73, 95% CI 2.47 to 9.06) but not in the short term (aOR 1.34, 95% CI 0.52 to 3.49).ConclusionsWe demonstrate an independent association between COVID-19 and increased risk of economic vulnerability among COVIDENCE participants, measured by both household income sufficiency and sickness absence from work. Taking these findings together with pre-existing research showing that socioeconomic disadvantage increases the risk of developing COVID-19, this may suggest a ‘vicious cycle’ of impaired health and poor economic outcomes.Trial registration numberNCT04330599.

Air pollution is a major public health concern, and large numbers of epidemiological studies have been conducted to quantify its impacts. One study design used to quantify these impacts is a spatial areal unit design, which estimates a population-level association using data on air pollution concentrations and disease incidence that have been spatially aggregated to a set of nonoverlapping areal units. A major criticism of this study design is that the specification of these areal units is arbitrary, and if one changed their boundaries then the aggregated data would change despite the locations of the disease cases and the air pollution surface remaining the same. This is known as the modifiable areal unit problem, and this is the first article to quantify its likely effects in air pollution and health studies. In addition, we derive an aggregate model for these data directly from an idealized individual-level risk model and show that it provides better estimation than the commonly used ecological model. Our work is motivated by a new study of air pollution and health in Scotland, and we find consistent significant associations between air pollution and respiratory disease but not for circulatory disease. K E Y W O R D S epidemiological study, nitrogen dioxide and particulate matter, spatially aggregated disease counts 1 INTRODUCTION Air pollution continues to be a major global public health problem, with the World Health Organisation (WHO) linking seven million deaths to it each year worldwide (World Health Organisation, 2016). In the United Kingdom an estimated 40,000 deaths are attributed to air pollution exposure each year (Royal College of Physicians, 2016), and legal limits for individual air pollutants have been stipulated that must not be exceeded (Department for the Environment, Food and Rural Affairs, 2015). The choice of these limits is informed by epidemiological studies, and both individualand ecological (or group)-level study designs are prevalent in the literature. Ecological-level studies are popular because they utilize available population-level disease incidence data, which makes them comparatively fast and inexpensive to implement. However, all that can be inferred is a population-level association rather than an individual-level causal relationship, and wrongly assuming the two are the same is known as ecological bias (Wakefield & Salway, 2001). Such bias is due in part to within-population variation in pollution exposures and disease incidence, because one does not This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

BackgroundSocio-economic deprivation is well recognised as a risk factor for developing COVID-19. However, the impact of COVID-19 on economic vulnerability has not previously been characterised.ObjectiveTo determine whether COVID-19 has a significant impact on adequacy of household income to meet basic needs (primary outcome) and work absence due to sickness (secondary outcome), both at the onset of illness (acutely) and subsequently (long-term).DesignMultivariate mixed regression analysis of self-reported data from monthly on-line questionnaires, completed 1st May 2020 to 28th October 2021, adjusting for baseline characteristics including age, sex, socioeconomic status and self-rated health.Setting and ParticipantsParticipants (n=16,910) were UK residents aged 16 years or over participating in a national longitudinal study of COVID-19 (COVIDENCE UK).ResultsIncident COVID-19 was independently associated with increased odds of participants reporting household income as being inadequate to meet their basic needs, both acutely (adjusted odds ratio [aOR) 1.39, 95% confidence interval [CI] 1.12 to 1.73) and in the long-term (aOR 1.15, 95% CI 1.00 to 1.33). Exploratory analysis revealed the long-term association to be restricted to those who reported ‘long COVID’, defined as the presence of symptoms lasting more than 4 weeks after the acute episode (aOR 1.39, 95% CI 1.10 to 1.77). Incident COVID-19 associated with increased odds of reporting sickness absence from work in the long-term (aOR 5.29, 95% CI 2.76 to 10.10) but not acutely (aOR 1.34, 95% CI 0.52 to 3.49).ConclusionsWe demonstrate an independent association between COVID-19 and increased risk of economic vulnerability, both acutely and in the long-term. Taking these findings together with pre-existing research showing that socio-economic disadvantage increases the risk of developing COVID-19, this may generate a ‘vicious cycle’ of impaired health and poor economic outcomes.Trial registrationNCT04330599Summary BoxWhat is already known on this topicSocioeconomic deprivation is recognised as a major risk factor for incidence and severity of COVID-19 disease, mediated via factors including increased occupational and household exposure to SARS-CoV-2 and greater physical vulnerability due to comorbiditiesThe potential for COVID-19 to act as a cause, rather than a consequence, of economic vulnerability has not previously been characterised.What this study addsWe demonstrate an independent association between incident COVID-19 and subsequent self-report of household income being inadequate to meet basic needs, both acutely and in the long termIncident COVID-19 was also associated with increased odds of subsequent self-report of sickness absence from work in the long-term.