Knowledge of five diseases caused by smoking and secondhand smoke may not have improved among adults who smoked across 46 countries over about 20 years.
Investigators analyzed nationally representative data from 133,410 adults who participated in the 2002 to 2022 International Tobacco Control (ITC) Project in 26 countries and 110,537 adults who participated in the 2008 to 2020 Global Adult Tobacco Survey (GATS) in 32 countries. ITC used longitudinal cohort surveys with replenishment, whereas GATS used repeated cross-sectional household surveys. The datasets were analyzed separately.
The investigators assessed whether participants knew or believed that smoking causes lung cancer, cardiovascular disease or heart attack, and stroke as well as whether secondhand smoke causes lung cancer and cardiovascular disease or heart attack among individuals who do not smoke. They estimated country-level knowledge and changes over time for all five outcomes and examined consistency between ITC and GATS estimates in 12 countries included in both surveys.
Knowledge that smoking causes lung cancer was highest, at 92% in both ITC and GATS. Awareness was lower for cardiovascular outcomes: 85% of ITC participants knew smoking can cause cardiovascular disease, compared with 80% of GATS participants who knew it could cause heart attack. Knowledge that smoking can cause stroke was 75% in ITC and 66% in GATS.
Knowledge of secondhand smoke–related harms was also lower. Awareness that secondhand smoke can cause lung cancer was 77% in ITC and 82% in GATS, whereas 62% and 73%, respectively, knew that exposure could cause heart attack or cardiovascular disease.
The near-zero overall change masked differences across countries and outcomes. Knowledge that smoking can cause stroke increased significantly in 11 ITC countries and three GATS countries but did not change significantly in 13 ITC countries and seven GATS countries. Knowledge that smoking or SHS can cause cardiovascular disease or heart attack remained unchanged in many countries.
The investigators reported gains in the knowledge of cardiovascular risks associated with smoking or secondhand smoke in several low- and middle-income countries, including Bangladesh, India, Thailand, and Vietnam. Knowledge remained low in Nigeria and Ethiopia, while some measures declined from relatively high baseline levels in Germany and Japan. Overall, gains were offset by little change or declines elsewhere, resulting in the average net increase of 0.14 percentage points per year across the five outcomes.
Across the 12 countries included in both surveys, correlations between the estimates ranged from 0.60 to 0.81 across the five knowledge indicators. However, correlations for the two secondhand smoke outcomes were not statistically significant.
The investigators noted that self-reported knowledge could be affected by recall or social desirability bias and that low response rates in some ITC surveys could limit generalizability. Differences between ITC and GATS in research design, sampling, survey timing, and questions used to measure knowledge also warranted caution when comparing estimates.
The primary findings were limited to adults who currently smoked tobacco. The investigators cautioned that the near-zero net change might not reflect trends in the overall population because knowledge could have changed differently among former or never-smokers.
“The near-zero net change in knowledge over time underscores the need for comprehensive, well-implemented and enforced tobacco control strategies,” wrote lead study author Janet Chung-Hall, of the School of Psychology at the University of Waterloo, and colleagues.
Full disclosures of the study authors can be found in the study.
Source: BMJ Open
