Frequencies and Circumstances of Falls in the National Institute for Longevity Sciences , Longitudinal Study of Aging ( NILS-LSA )

Frequencies and circumstances of falls were assessed among 1030 middle-aged and elderly people who participated in the NILS-LSA (National Institute for Longevity Sciences, Longitudinal Study of Aging) from November, 1997 to March, 1999 and responded to the questionnaires. The variables analyzed in the present study were demography and history of falls in the past one year. Circumstances of falls, e.g. time, location, activities associated with falls, cause of falls and degree of injury due to falls were asked when the subjects experienced a fall. Fear of falling was also investigated in all subjects. The prevalence of falls was 12.9% in the middle-aged group (40-59yr.) and 16.5% in the elderly group (60-79yr.). The distribution of time, location, activity associated with falls, cause and injury due to falls corresponded with previous fall studies among community-dwelling elderly people. The incidence of falls was extremely high during the daytime and outdoors. Falls occurred most frequently while walking. The majority of falls were due to extrinsic factors. About 40% of all falls caused no injury. As to the fear of falling, about 30% of the middle-aged subjects and about 60% of the elderly subjects reported that they were fearful. Our results suggested that fall accidents are not rare, even in middle-aged people. J Epidemiol, 2000 ; 10 : S90-S94.


INTRODUCTION
Falls are one of the most important problems among the elderly i-a).They constitute a serious threat to life, health and quality of life 4).In Japan about 20% of community-dwelling elderly people fall at least once during a year 5).It is said that the frequency of falls increases with advancing age 4).However, there are very few studies which have investigated the frequencies of falls among the middle-aged and compared the frequencies between middle-aged and elderly people.
The purpose of the present study was to assess the prevalence and circumstances of falls among the participants in the NILS-LSA (National Institute for Longevity Sciences, Longitudinal Study of Aging) 6) consisting of middle-aged and elderly people.It is thought to be valuable to describe the frequencies and circumstances of falls in community-dwelling adults, including the middle-aged as well as the elderly, for the prevention of falls in the community.

MATERIAL AND METHODS
The subjects were 1126 people who participated in the NILS-LSA from November, 1997 to March, 1999.The NILS-LSA is a multidisciplinary longitudinal project conducted by the Department of Epidemiology, the National Institute for Longevity Sciences 6).Out of these subjects, 1030 persons responded to the questionnaires concerning fall accidents (Table 1).
The variables analyzed in the present study were demography and history of falls in the past one year.Circumstances of falls, e.g.time, location, activities associated with falls, cause of falls and degree of injury due to falls were also asked when the subjects experienced a fall.The causes of falls were classified according to Haga et al .7), whose classifications were simple and practical: due to environmental factors (extrinsic), due to the subject him/herself (intrinsic) and origin unknown.When the subjects had fallen more than twice a year, the cir-Department of Epidemiology, National Institute for Longevity Sciencies .
Address for correspondence : Naoakira Niino, Department of Epidemiology, National Institute for Longevity Sciencies , 36-3 Gengo M orioka-cho Obu, Aichi, 474-8522 Japan.cumstances of falls were questioned regarding the fall resulting in the most serious injury.Fear of falling was also investigated in all subjects according to their response to an ordered-choice, closed-ended question about a general fear of falling ("Are you afraid of falling?").In the present study, falls were defined as "events that cause subjects to fall to the ground or other lower level against their will" which was merely a modification of the definition proposed by Gibson 8).
The prevalence of falls (rate of subjects with falls in the year preceding the survey) was assessed and compared in the middle-aged group (aged 40 to 59) and the elderly group (aged 60 and older).Statistical analysis was done using the X -square test.Circumstances of falls were investigated for the falls resulting in the most serious injury.Thus, not all the falls were recorded either in the middle-aged group or the elderly group.
As the proportion of recorded falls to all falls might be different from the middle-aged to the elderly, it was difficult to compare the general condition strictly on when, where, or how the fall occurred between two age groups using our results.Therefore, as to the circumstances of falls, simple descriptive data were reported in this paper.These data were analyzed using the Statistical Analysis System (SAS) release 6.12.

RESULTS
The prevalence of falls (rate of subjects with falls) is shown in Table 2.It was 8.9% in the middle-aged group and 14.4% in the elderly group for males.The prevalence was significantly higher in the elderly.For females, it was 17.2% in the middleaged group and 18.6% in the elderly group.There was no significant difference between the two age groups.Although females tended to have a higher prevalence than males, a significant difference was found only in the middle-aged group.
The distribution of time when the falls occurred is shown in Table 3.In both age groups, falls were much more common during the daytime.
As to the location of falls, outdoor falls were much more frequent than indoor falls.For the middle-aged, 69.0% of all falls occurred outdoors and for the elderly 75.0%occurred out- doors.
Activities associated with falls were classified as shown in Table 4. Except for others/unknown, falls most frequently occurred while walking, followed by descending stairs in both age groups.
The main cause of falls identified by our classification were: 83.3% extrinsic falls, 1.5% intrinsic falls and 15.2% unknown for the middle-aged group and 76.5% extrinsic falls, 7.4% intrinsic falls and 16.1% unknown for the elderly group (Table 5).
The majority of falls were due to extrinsic factors in both age groups.About 40% of all falls caused no injury in either age group (Table 6).In the middle-aged, only 1 fall (1.5%)led to a fracture and in the elderly 6 falls (7.4%) led to a fracture.There were no hip fractures.
As to the fear of falling, about 30% of all middle-aged subjects and about 60% of all elderly subjects reported that they were fearful (Table 7).The difference in the prevalence of fear  of falling was statistically significant between the two age groups.

DISCUSSION
The prevalence of falls was 12.9% in the middle-aged group and 16.5% in the elderly group.Although the elderly tended to fall more frequently, there was no significant difference.There have been some studies on falls in community-dwelling elderly in Japan 9-12).The reported prevalence rates were around 20%, which were similar to our result in the elderly group.For Japanese middle-aged people, we have little comparable data.However, according to our result, fall accidents are not rare even in middle-aged people.
Previous studies have found a higher fall rate in females' u, 19) In the present study, females tended to have a higher prevalence than males but significant difference was found only in the middle-aged group.
The distribution of time, location, activity associated with falls, cause and injury due to falls corresponded to previous fall studies among community-dwelling elderly 9.12-16).The incidence of falls was extremely high during the daytime and outdoors.Falls occurred most frequently while walking.The majority of falls were due to extrinsic factors.About 40% of all falls caused no injury.There seemed to be little difference in the circumstances of falls between the middle-aged group and the elderly group.However, with extrinsic causes, the proportion of tripping was much higher in the middle-aged than in the elderly.As to prognosis, fractures were more frequent among the elderly.These results suggested that falls among the elderly may not be completely the same as falls among the middleaged.
The prevalence of fear of falling was significantly higher among the elderly group than among the middle-aged group.This result is consistent with a previous study which reported the increase in fear of falling with age 16).Younger people may be reluctant to admit to have a fear of falling.There have been quite a few epidemiological studies on fear of falling in Japan.However, this fear can lead to a debilitating spiral marked by loss of confidence and reduce activity, resulting ultimately in a loss of independence 17).Further studies are needed on the fear of falling.
This study had several limitations.First of all, because the subjects of this study did not include all the participants in the NILS-LSA, we have to be prudent in generalizing the results.Secondly, since all measurements were based on the subjects' memory and self-rating, the objective reliability of the results is somewhat limited.
However, the results obtained in the present paper reveal the frequencies and circumstances of falls not only in the elderly, but also in the middle-aged.These data provide useful information for the prevention of falls in community-dwelling populations.
This study is part of a multidisciplinary project.Therefore, we have investigated other medical, psychological and sociological variables.In the next stage, we intend to analyze risk factors on falls in the middle-aged and elderly people by investigating the relationships between falls and other variables.

Table 1 .
Age and gender distribution of the respondents.

Table 2 .
Number and rate of subjects with falls.

Table 3 .
Distribution of the time of day.

Table 5 .
Distribution of the main causes of falls.

Table 6 .
Distribution of injuries due to falls.

Table 7 .
Number and rate of subjects with fear of falling.