| Summary: | Introduction
Smoking-attributed mortality is increasing steadily in most developing
countries. The aim of the study is to assess the reduction in smoking-associated
mortality following cessation.
Methods
Death data were collected from 2016 to 2017. Cases were deaths from
pre-defined diseases of interest (65298); controls were deaths from pre-defined
non-smoking-related diseases (13527). Case versus control odds ratios for exsmokers
versus smokers were calculated by age, sex, marital status and education
with standardized logistic regression. These are described as mortality rate ratios
(RRs, calculated as odds ratios), with a group-specific confidence interval (CI).
The statistical analysis of the data was conducted from June to August 2019.
Results
For deaths from pre-defined non-smoking-related diseases at age 35–59
years, the RRs for quitting smoking 0–4, 5–9 or ≥10 years ago and never smoking
were 0.66 (95% CI: 0.55–0.78), 0.58 (95% CI: 0.38–0.88), 0.61 (95% CI: 0.45–
0.82), and 0.43 (95% CI: 0.39–0.46), respectively. The same trend was found
at ages 60–69 years and 70–79 years. Younger age of quitting (25–44 or 45–64
years) appeared to be associated with greater protection among the age groups:
RR was 0.55 (95% CI: 0.42–0.74) and 0.67 (95% CI: 0.56–0.79), respectively,
at age 35–59 years. Among the patients who died of lung cancer, the strong
protective effect can only be observed when the duration of quitting is ≥10 years.
The effect of smoking cessation on the risk of death from cardiovascular disease
can be observed when the duration of quitting is 1–5 years.
Conclusions
Longer durations of smoking cessation are associated with progressively
lower mortality rates from the diseases of interest, such as lung cancer and
other smoking related cancers. For sustainable monitoring of tobacco-attributed
mortality, smoking information over decades, such as smoking duration and quit
smoking years, should be recorded during registration of death.
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