Modeling complexity of EMA data: time-varying lagged effects of negative affect on smoking urges for subgroups of nicotine addiction.

INTRODUCTION

Ecological momentary assessments (EMA) are increasingly used in studies of smoking behavior. Through EMA, examination of lagged relationships is particularly useful for establishing a temporal order of events and for identifying types and timing of risk factors. The time-varying effect model (TVEM) handles EMA data challenges and addresses unique questions about the time-varying effects.

METHODS

Generalized TVEM was applied to EMA data from a smoking cessation study to investigate a "time-varying lagged" effect of negative affect on high smoking urges. Participants included 224 smokers with a smoking history of 23.1 years (SD = 9.8) smoking 27.3 cigarettes per day (SD = 10.7), which provided 11,394 EMAs following a quit attempt and prior to a smoking lapse.

RESULTS

The effect of negative affect was found to vary as a function of a time lag, with stronger immediate effects: estimated odds ratio (OR) of 2.7 for the lower nicotine-dependence group (time to first morning cigarette > 5 min, 57.6%) and OR of 2.4 for the higher nicotine-dependence group (≤ 5 min). The magnitude of the effect persisted up to 7 hr while decreasing over time.

CONCLUSIONS

This analysis confirmed the importance of negative affect as a precursor of smoking urges while showing that the magnitude of the effect varies over time. An assumption of a constant lagged effect may bias estimates of the relationships and fail to provide a comprehensive outlook of the relational dynamics.