AIMS: To evaluate statewide policies restricting e-cigarette nicotine strength.

DESIGN: A difference-in-difference regression analysis was used to compare e-cigarette sales in states that restrict nicotine strength with states with no restrictions. Because flavor restrictions might affect sales and nicotine strength, states with flavor restrictions were also assessed.

SETTING AND CASES: United States e-cigarette retail sales data during January 2017 to March 2022 were licensed from Information Resources Incorporated. States with restrictions included Massachusetts (restricted maximum nicotine strength to 3.5% and nontobacco flavored e-cigarette sales in December 2019); Utah (restricted nicotine strength to 3.6% in September 2021); and Rhode Island, New York and Washington (restricted nontobacco flavor sales in October 2019, May 2020 and October 2019 to January 2020, respectively). These were compared with data from 34 states with no e-cigarette nicotine strength or flavor restrictions.

MEASUREMENTS: Weighted mean nicotine strength and total unit sales. Total unit sales per 1000 state population were summed into 4-week periods by state. Models controlled for emergency responses, state demographics, tobacco control policies, time and state fixed effects.

FINDINGS: Restricting both nicotine strength and flavors in Massachusetts was associated with a 2.04 percentage point (pp) reduction in mean nicotine strength and 86.76-unit reduction in monthly unit sales per 1000 persons compared with states with no restrictions (all P < 0.01). Restricting nicotine strength only in Utah was associated with a 1.77 pp (P < 0.01) reduction in mean nicotine strength; however, there was no impact on unit sales. Restricting nontobacco flavor sales only in Rhode Island, New York and Washington slightly reduced mean nicotine strength (0.21, 0.62 and 0.19 pp, respectively) and sales (36.66, 34.51 and 16.37 units, respectively) (all P < 0.01).

CONCLUSIONS: United States statewide policies restricting e-cigarette nicotine strength appear to be associated with reductions in average nicotine strength in sales within that state; however, there appears to be no impact on unit sales. When these policies are implemented along with flavor restrictions; reductions in average nicotine strength occur in addition to reduced unit sales.