Smoking at any level is a significant risk factor for the development of cardiovascular disease. Light smoking (1-4 cigarettes per day) still increases risk of disease about 3 times and occasional non-daily smoking has been shown to increase the risk of cardiovascular and total mortality.
Bjartveit K, Tverdal A. Health consequences of smoking 1–4 cigarettes per day. Tob Control. 2005;14:315–320.
Luoto, et al. Occasional smoking increases total and cardiovascular mortality among men. Nicotine Tob Res. 2000;2:133–139.