Fall Risk Prediction in Community Dwelling Hong Kong Elderly Chinese Based on their 12-Month Prospective Fall History, Longest Pre-Retirement Occupation and Bone Mineral Density

Introduction

Falls have been public health concerns among the elderlies since 1940 [1, 2]. In advancing age with reduced bone mineral density (BMD), the consequence of fall is fragility fracture or even fatality [3]. The US experience tells that one-third of people aged 65 or above experience “falls” at least once every year and are the main source of patients seeking emergency medical services [4, 5, 6, 7]. Comparing with US, people in Hong Kong are living in a densely occupied condition with the longest life expectation [8]. Previous studies show that 18% of the community dwelling elderly fell at least once a year, and 40% of fallers had multiple falls. Fall caused fractures in more women (8.5%) than men (4.6%) attending the emergency medical services, with 17.4% of fallers needed hospitalization. Subsequent follow up for 9 months and found that 21.8% elderly fell again [9, 10, 11].

Older adults with poor self-perceived health, dizziness, presence of cardiovascular accidents (CVA), difficulties in aids daily living (ADL), body mass index (BMI) of between 20 to 24 (i.e., normal to slightly obese), slow gait velocity, and non-practice of morning walk, frequent use of analgesics balms or plasters, and previous white-collar employment were the common reasons of falls [11, 12, 13, 14]. This study aimed to investigate and predict the fall risk based on the fall incidence, longest pre-retirement occupation and bone mineral density in community dwelling Hong Kong Chinese elderly.

Methods

3,983 men and women community-dwelling ambulatory Hong Kong Chinese of age older than 65 were randomly recruited from 18 different community districts throughout Hong Kong territory using the cluster sampling through advertisement via community senior citizens clubs and neighborhood elderly houses. Their fall history and frequency in a 12-month prospective cohort were collected, and the association with their longest pre-retirement occupations and bone mineral density were evaluated.

Subjects’ inclusion criteria were Community dwelling elderly males or females of age 65 or above, able to walk without assistance to the research center for the assessment, understanding and signing the consent form. Exclusion criteria were bilateral hip replacement or spine surgery done, known malignancy and unable to attend the research center for receiving assessment and giving consent.

Sample size calculation is based on the results of the similar community lifestyle and risk factors study [15]. The sample size of 2,000 men and 2,000 women in this study should be adequate to attain 90% power. The data were from part of the Mr and Ms OS Study. Ethic approval was granted from The Chinese University of Hong Kong Ethics Committee (CREC-2003.102). Written informed consent was obtained from all subjects.

Subjects’ bone mineral density (BMD) was measured by QDR-4500W Hologic Densitometer to group under the categories of Normal, Osteopenia and Osteoporosis using the World Health Organization criteria. Demographic data including subjects’ profile, fall history and longest pre- retirement occupation were collected. Physical Activity Scale for the Elderly Questionnaire (PASE) was used to evaluate their physical mobility. Fall frequency telephone survey was conducted at every four-month interval for twelve prospective months to all subjects.

SAS, Version 9.4 was used for statistical data analysis. Subjects’ profiles were compared in separate genders. Two sample independent t-tests were used for continuous variables while Chi-square tests for categorical variables. The incidence of falls was calculated per 1,000 person-years. All statistical tests were two-sided. A α-level of 5% was used as the level of significance.

Results

Subjects recruited from 18 districts throughout Hong Kong were 1,983 women (aged 72.58±5.4) and 2,000 men (aged 72.39±5.01). Both males and females were of similar age and similar number for comparison and analysis.

a = p-value of chi-square test for trend, b = p-value of Poisson Regression, *p-value <0.001, Poisson Regression comparing female with male Table 1: Incidence of fall (males).

Fall incidence per 1,000 person-years in women (Table 2) and men (Table 1) was 245.75 and 158.60 in osteoporosis, 246.99 and 152.98 in osteopenia, and 252.35 and 182.57 in normal BMD (p<0.001). Women had higher fall incidence than in men (p<0.001). Older age (73.3± 5.2) had 2 or more falls than no fall in younger age (72.1± 4.8) [RR (95% CI) 1.21 (1.14, 1.28) per 5 years increase]. PASE scores were 92.0±48.8 in older age and 98.4±49.9 in younger age [RR (95% CI): 0.93 (0.87, 0.99) per 50-unit increase].

Pre-retired longest occupation in Building/Maintenance jobs showed the lowest fall risk [RR (95% CI): 0.58 (0.37, 0.90)], followed by Business/Finance [RR (95% CI): 0.80 (0.68, 0.95)] and Art/Design/Office [RR (95% CI): 0.81 (0.68, 0.97)] as compared to Management jobs as a standard reference.

a = p-value of chi-square test for trend, b = p-value of Poisson Regression, *p-value <0.001, Poisson Regression comparing female with male Table 2: Incidence of fall (Females).

Discussion

In elderly men, the incidence of falls was higher in the normal BMD group than in the reduced BMD group (p≤0.01). In elderly women, the incidence of falls did not show a relationship with reduced BMD (≤0.01). Although the incidence of falls was higher in the Normal BMD Group in Hong Kong Chinese elderly men, it was similar among the Normal Group, Osteopenia Group, and Osteoporosis Group in Hong Kong Chinese elderly women. Collectively, the results of this study show that in Hong Kong Chinese older adults, women had a higher fall risk than men in advancing age.

Building or maintenance job retirees show the lowest fall risk [RR (95% CI): 0.58 (0.37, 0.90)] probably due to their job requirements for a good physique in an outdoor environment, and a regular physical work with better balance. The combination helps to prevent osteoporosis and falls as weight-bearing exercise and vitamin D from the sunlight are the known factors to prevent osteoporosis. The lowest relative risk gives a reasonable prediction for their subsequent fall risk except if there is a deterioration of their physical and medical health (Table 3).

The relative risk of Business/Finance retirees [RR (95% CI): 0.80 (0.68, 0.95)] and Art/Design/Office retirees [RR (95% CI): 0.81 (0.68, 0.97)] are of the medium fall risk. Business and finance retirees and Art/Design/Office retirees mainly worked indoors and in sedentary work nature. The risk of developing osteoporosis is higher if they do not have adequate calcium and vitamin D, and lack of physical weight- bearing exercises. If business and finance retirees, mainly white-collar workers, have osteoporosis and sustained a fall, their risk of vertebral fracture is also likely [12, 13].

Food preparation retirees show the highest frequency of falls of 2 or more (17.8%) and highest relative risk of fall of [RR (95% CI): 1.01 (078, 1.31)]. As food preparation retirees stay in the static position doing their job, the lack of body displacement in prolonged static positions may impair balance and proprioception capability, making them prone to fall, as frequent physical activity improves balance and reaction time [16, 17, 18, 19, 20].

Bone Health and Osteoporosis Foundation predicts one in every two osteoporosis sufferers will eventually sustain a fracture [21]. Literature on fall risk reports one in five elderly individuals aged 65 or above falls annually, with 24.8% of fallers experiencing fractures, and 72.2% having life- threatening conditions such as head injuries [10, 11, 18, 19].

In people with reduced BMD, the consequence of a fall could be fragility fracture or even fatality. Health education and promotion are effective ways to raise public awareness and improve individuals’ knowledge of osteoporosis care and control within a short time [12, 13, 19, 20, 22]. Health care professionals should collaborate with local television networks, radio stations, and newspapers, to educate and promote osteoporosis, fragility fracture and fall prevention to the public [12, 13, 14].

Limitations of this Study

All subjects were ambulatory older adults without bilateral hip replacement to attend the research center for assessments. The sampling may have only included older adults with better balance skills and less falls in this study compared to frail and fragile osteoporotic older adults with poor balance and higher fall risks, leading to an underestimation of fall risks.

Conclusion

All subjects were ambulatory community-dwelling individuals recruited locally through community activities and community advertising. The results are representative. In Hong Kong Chinese women, falls are common once they reach the age of 65, regardless of their BMD status. People with reduced BMD are at risk of sustaining fragility fractures when they fall. Health education and promotion are extremely important. Recognizing the longest re-retirement jobs could have impact on the fall risk help to give indication and guideline for early fall risk detection and prevention. Retirees in the food preparation area have a high fall risk. The data of this study provides useful and functional information on fall risk identification, detection, and prevention. Strategies to minimize falls and prevent the first fracture should be examined in further detail.

Acknowledgement

This study was partially funded by the National Institute of Health (NIH) Grant R01-AR049439‐01A1 (Mr OS Project) and a direct grant for research of The Chinese University of Hong Kong (Ms OS Project).