Urbanization and hospital admission rates for alcohol and drug abuse: a follow-up study of 4.5 million women and men in Sweden.

AIMS: This study analyses whether the level of urbanization is associated with hospital admissions for alcohol and drug abuse, after adjustment for individual demographic and socio-economic characteristics.
DESIGN: Follow-up study from 31 December 1996 to 31 December 1999.
SETTING: Sweden. PARTICIPANTS: The entire Swedish population aged 25-64 yeras, in total 4.5 million women and men. MEASUREMENTS: Hospital admission rates for alcohol abuse (12,812 events) and drug abuse (6459 events). Level of urbanization was defined by population density and divided into quintiles. Cox proportional hazard models were used to analyse the data.
FINDINGS: The results showed an apparent gradient for both women and men; with increasing level of urbanization the hospital admission rates for alcohol abuse and drug abuse increased sharply. After adjustment for age, marital status, education and immigrant status, the hazard ratios for hospital admission for alcohol abuse were 1.76 [confidence interval (CI) = 1.58-1.96] for women and 1.71 (CI = 1.60-1.82) for men in the most densely populated areas (quintile 5). For drug abuse the corresponding hazard ratios were 1.89 (CI = 1.67-2.15) for women and 2.38 (CI = 2.12-2.67) for men.
CONCLUSIONS: A high level of urbanization was associated with increased hospital admission rates for alcohol abuse and drug abuse. The level of urbanization should be considered in the distribution of resources for prevention and treatment of alcohol and drug abuse.