The objective of the study was to evaluate the relation between every-night (habitual) snoring, sleep apnea and cognitive complaints (concentration and memory problems) in an adult population-based sample. In the Dan-MONI-CA (MONItoring trends in CArdiovascular diseases) 1,504 males and females aged 30, 40, 50 and 60 years were classified according to their snoring habits. Nocturnal respiration was measured in 748 participants. The following measures were regarded as potential confounders: age, gender, unintended sleepiness, insomnia, depression, hypnotic use, alcohol and tobacco consumption by questionnaire, body mass index (BMI) and blood pressure. Concentration and memory problems were both related to depression, insomnia and unintended sleepiness. Snoring and sleep apnea (defined as a respiratory distress index – RDI ≧ 5), were associated with concentration problems and unintended sleepiness. The odds ratios (95% confidence intervals) between snoring, concentration and memory problems, calculated by logistic regression analysis after adjustments of the above confounders, were 1.90 (1.23-2.91, p < 0.01) and 1.38 (0.97-1.99, NS). For those with sleep apnea, the odds ratios were 3.53 (1.42-8.73, p< 0.001) and 1.51 (0.81-2.14, NS) for concentration and memory problems, respectively. The main conclusion drawn from this study is that cognitive complaints show a high correlation to mood, insomnia and hypersomnia. Habitual snoring and sleep apnea show a correlation to concentration problems, but not to memory complaints. This suggests that part of the association between snoring, sleep apnea and cognitive dysfunction is related to the presence of sleep disturbances and daytime sleepin