[Sociomedical and life-style risk factors of senile dementia, determined in a nested case-control study].

To explore the sociomedical and life-style risk factors associated with the development of senile dementia, we conducted a nested case-control study with the following subjects: cases were those who underwent health examination for the aged in 1979-1980 in a town in Aichi Prefecture and nineteen cases identified as having senile dementia 13-14 years later. Two controls per case were randomly selected from those who underwent the same health examination and were proven not to have dementia up to 1993, with thirty-eight controls matched to each case for sex, age at first examination (+/- 2 years), and residential area. Routine odds ratio analysis demonstrated the following relationships between onset of senile dementia and sociomedical and life-style factors of 13-14 years ago. (A) factors significantly associated with an increased risk of dementia were (1) difficulty in using fingers (odds ratio--12.1; 95% confidence interval--1.54-94.7), (2) alcoholic beverage drinking habits (6.00; 1.07-33.5), (3) use of false teeth (3.50; 1.10-61.6), (4) less frequent chance to converse (3.85; 1.15-12.5), (5) much spare time (3.70; 1.43-25.0), (6) decrease of number of friends (2.77; 1.12-11.1), and (7) inability to calculate subtractions such as 29-17 (3.33-33.3). On the contrary, (B) habitual physical activities significantly reduced the risk of developing senile dementia (0.27; 0.05-0.71). (C) cigarette smokers and regular users of sleeping pills were not at greater risk of subsequent senile dementia, to which such personal characteristics as shyness and nervousness were not significantly linked.