# Association of smoking behavior and time to first cigarette with all-cause and cause-specific mortality: A cohort analysis from the NHANES 2001–2018

## TL;DR

This study finds that smoking behavior, especially smoking within 30 minutes of waking, strongly increases mortality risks from all causes and cardiovascular disease.

## Contribution

The study reveals a U-shaped relationship between time to first cigarette and mortality risks, particularly for cardiovascular disease.

## Key findings

- Former and current smokers had higher mortality risks compared to never smokers.
- Smoking within 30 minutes of waking was linked to the highest all-cause and cardiovascular disease mortality risks.
- Time to first cigarette showed an inverse relationship with cancer mortality.

## Abstract

Smoking is a major risk factor for death, but the impact of behavioral patterns such as time to first cigarette (TTFC) on this risk has been little studied in the US population. To address this, we investigated the association between smoking status and TTFC with all-cause, cardiovascular disease, and cancer mortality based on a national sample.

We conducted a pooled secondary data analysis of the National Health and Nutrition Examination Survey data from the United States, covering nine continuous cycles between 2001 and 2018. The initial pooled sample comprised 91355 participants. After applying a series of exclusion criteria, the final analytical cohort consisted of 39084 adult subjects. TTFC was investigated by means of a touch-screen questionnaire. Outcomes included all-cause mortality, cardiovascular disease mortality, and malignancy-related mortality. Mortality information was obtained from the National Death Index (NDI) using death certificates (https://www.cdc.gov/nchs/linked-data/mortality-files/?CDC_AAref_Val=https://www.cdc.gov/nchs/data-linkage/mortality-public.htm).

After full adjustment, former smokers had a significantly elevated risk of mortality compared to never smokers. A U-shaped association was observed between TTFC and both all-cause and CVD mortality. For all-cause mortality, the risk was highest in smokers with TTFC <30 min (hazard ratio, HR=4.47; 95% CI: 2.23–8.98, p<0.001). Similarly, for CVD mortality, the highest risk was also found in the TTFC <30 min group (HR=5.53; 95% CI: 2.32–13.14, p<0.001). In contrast, TTFC showed an inverse relationship with cancer mortality, with the risk being highest for TTFC <30 min (HR=3.23; 95% CI: 1.25–8.31, p=0.020) and decreasing with a later TTFC.

Former and current smokers showed elevated all-cause, CVD, and cancer mortality risks versus never smokers. TTFC exhibited a U-shaped association with all-cause and CVD mortality, but not with cancer mortality.

TTFC: time to first cigarette, NHANES: National Health and Nutrition Examination Survey, NDI: National Death Index, NCHS: National Center for Health Statistics, CDC: Centers for Disease Control and Prevention, HEI-2020: Healthy Eating Index, GED: General Educational Development, PIR: poverty-to-income ratio, BMI: body mass index, CVD: cardiovascular disease, TC: total cholesterol, ALT: alanine aminotransferase, AST: aspartate aminotransferase, HbA1C: glycated hemoglobin, WTDR1D: dietary one-day sample weight