Is individual smoking behaviour influenced by area level ethnic density? A cross-sectional electronic health database study of inner south-east London

Problem

Substantial ethnic differences in the number of cigarettes smoked per day have been shown to exist. Given that ethnic differences in smoking intensity may account for ethnic differences in the prevalence and severity of COPD, identifying strategies to reduce smoking rates in ethnically diverse populations is a key public health priority. Previous literature has shown that individuals living in an area with a greater proportion of their own ethnic group are less likely to experience poor mental health outcomes than those living in area of greater ethnic isolation. Whether this ethnic density effect extends to other major health outcomes remains to be explored.The aim of this study was to determine the extent to which ethnic differences in smoking intensity are related to neighbourhood level ethnic composition.

Approach

Routinely-collected primary care data from Lambeth, Newham, Tower Hamlets and Hackney were used for this cross-sectional database study. The most recent value for cigarettes per day (CPD) was categorized into low and high intensity (>20 CPD). Self-reported patient ethnicity was collapsed into seven categories of white British, Irish, Indian, Pakistani, Bangladeshi, Pakistani, African, and Caribbean. Ethnic density was defined as the percentage of people from each ethnic group living within each census LSOA, according to the 2011 Census.Multilevel logistic regression which nested patients within LSOAs within boroughs was conducted separately for each of the seven ethnic groups to explore whether living in an area of high ethnic density reduced the odds of being a high intensity smoker. The primary predictor was ethnic density. Additional confounders included age, gender, and Index of Multiple Deprivation score.

Findings

From 565,337 patients aged 18+ free from COPD or lung cancer, 106,859 patients were identified as current smokers (18.9%). 94% of current smokers had a cigarettes per day value recorded and were thus included in the analysis (N=100,354). A protective effect of ethnic density was evident for White, African, and Caribbean groups. The effect was largest for the Caribbean population, amongst whom a 10% increase in ethnic density was associated with a 42% reduction in the odds of being a high intensity smoker (OR 0.58 CI95% 0.41-0.83 p=0.003). For White and African groups, a 10% increase in ethnic density was associated with a 5% and 16% reduction in the odds of being a high intensity smoker respectively.

Consequences

Evidence of a strong protective effect of neighbourhood level ethnic density, most notably for African and Caribbean populations, suggests that proximity to one’s own ethnic group may be a significant factor in mitigating high risk smoking behaviour. Smoking cessation services may benefit from incorporating ethnic specific strategies, and addressing barriers which may face individuals living in greater ethnic isolation.