Associations of Smoking Status and Leisure-time Physical Activity with Waist Circumference Change – Ten-year Follow-up among Twin Adults
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BACKGROUND
This follow-up study investigated the associations of smoking status and leisure-time physical activity (LTPA) with weight circumference (WC) change.
METHODS
In the FinnTwin16 cohort, 3,431 twins (47% men) reported smoking status, LTPA, and WC in early adulthood and 10 years later. Regression models were conducted to investigate associations of smoking status and of LTPA change (metabolic equivalent tasks [MET]-h/week) with WC change (cm) during the follow-up. Within-pair associations were analyzed using linear mixed fixed-effect regression among 800 same-sexed (409 identical) pairs.
RESULTS
During the 10-year follow-up, 40% (n=454) quit smoking. Among those who quit smoking, the mean WC increase was 7.4 cm (SD 8.2) and the mean LTPA decrease was -0.02 MET-h/week (SD 35.8). Compared to individuals continuing daily smoking, only quitters who smoked daily at baseline (β 1.87; 95% CI 0.68, 3.06) increased their WC. This association was not robust after shared familial influences were controlled for. Each additional MET-h/week lowered the risk for WC increase among individuals who smoked occasionally (β -0.054; -0,08, -0.003), quitters who smoked daily (β -0.05; -0.06, -0.02) and those who had never smoked (β -0.04; -0.05, -0.03). In the analyses among identical twin pairs, LTPA was associated with less WC increase among those who quit occasional smoking or had never smoked. For quitters from daily smoking, this association approached significance, but no association remained for those continuing smoking.
CONCLUSIONS
Smoking cessation seems to be associated with WC increase, but familial confounding is involved in this process. LTPA may inhibit post-cessation WC increase.
KEY MESSAGES
This will be published as a summary box after the abstract in the final published article.
What is already known on this topic
1. Individuals quitting smoking tend to gain weight, but less is known of post-cessation abdominal obesity and the role of leisure-time physical activity in this process.
What this study adds
2. Smoking cessation associates with moderate increase in waist circumference among those who quit daily smoking, but shared familial influences are involved in this process.
3. Increase in leisure-time physical activity may prevent post-cessation waist circumference increase.
How this study might affect research, practice, or policy
4. More research is needed to unravel genetic and epigenetic mechanisms underlying post-cessation waist circumference increase.
5. In practice, individuals who quit smoking should be encouraged to be physically active.
