## 4 Discussion  
### Exercising Status  
Our study revealed that the frequency of exercise was associated with ADL and IADL functional abilities. Longitudinal analysis demonstrated that older adults who discontinued exercise had a significantly increased risk of subsequent ADL and IADL decline. Older adults who currently or consistently exercised exhibited decreased risks of ADL and IADL decline. The longitudinal associations of change in exercise status with subsequent IADL decline were stronger than those with subsequent ADL decline. Physical activity was reported to be associated with ADL and IADL disability [1,3]. Older adults who undertook more physical activities had a decreased risk of reporting functional limitations \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**ADL**} & \multicolumn{4}{c}{**IADL**} \\ \hline  & \multicolumn{2}{c}{**1999–2003 (\(n=2148\))**} & \multicolumn{2}{c}{**1999–2007 (\(n=1638\))**} & \multicolumn{2}{c}{**1999–2003 (\(n=2109\))**} & \multicolumn{2}{c}{**1999–2007 (\(n=1563\))**} \\ \cline{2-7}  & **AOR (95\% CI)** & \(p\) & **AOR (95\% CI)** & \(p\) & **AOR (95\% CI)** & \(p\) & **AOR (95\% CI)** & \(p\) \\ \hline Exercise status & \multicolumn{2}{c}{Reference **} & \multicolumn{2}{c}{Reference} & \multicolumn{2}{c}{Reference} \\ \multicolumn{1}{c}{} & 1.07 (0.78–1.47) & 0.6877 & 1.71 (1.23–2.38) & 0.0016 & 1.36 (1.00–1.83) & 0.0482 & 2.38 (1.61–3.51) & \(<\)0.0001 \\ \multicolumn{1}{c}{} & 0.21 (0.13–0.34) & \multicolumn{2}{c}{0.0001} & 0.17 (0.10–0.29) & \(<\)0.0001 & 0.62 (0.46–0.84) & 0.0021 & 0.46 (0.32–0.66) & \(<\)0.0001 \\ \multicolumn{1}{c}{} & 0.12 (0.08–1.07) & \(<\)0.0001 & 0.19 (0.13–0.27) & \(<\)0.0001 & 0.63 (0.49–0.80) & 0.0002 & 0.51 (0.38–0.69) & \(<\)0.0001 \\ \multicolumn{1}{c}{} & 0.95 (0.90–1.00) & 0.0400 & 0.96 (0.91–1.01) & 0.1068 & 0.98 (0.94–1.02) & 0.2473 & 0.95 (0.90–1.00) & 0.0331 \\ \multicolumn{1}{c}{} & 1.07 (0.99–1.16) & 0.0809 & 1.07 (0.99–1.16) & 0.0720 & 1.10 (1.04–1.17) & 0.0009 & 1.09 (1.02–1.17) & 0.0119 \\ \hline \end{tabular}
\end{table} 
Table 4: Multivariate logistic regression analysis of the associations of change of exercise status during 4- and 8 years, MNA score and number of diseases with ADL and IADL decline over 4- and 8-year periods *. \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**ADL**} & \multicolumn{4}{c}{**IADL**} \\ \hline  & \multicolumn{2}{c}{**2003 (\(n=2148\))**} & \multicolumn{2}{c}{**2007 (\(n=1638\))**} & \multicolumn{2}{c}{**2003 (\(n=2109\))**} & \multicolumn{2}{c}{**2007 (\(n=1563\))**} \\ \cline{2-7}  & \(\beta\) & \(p\) & \(\beta\) & \(p\) & \(\beta\) & \(p\) & \(\beta\) & \(p\) \\ \hline Exercise status & \multicolumn{2}{c}{Reference **} & \multicolumn{2}{c}{Reference} & \multicolumn{2}{c}{Reference} & \multicolumn{2}{c}{Reference} \\ \multicolumn{1}{c}{} & \(-\)0.26 & 0.2907 & 0.81 & 0.0200 & \(-\)0.39 & 0.2124 & 1.30 & 0.0009 \\ \multicolumn{1}{c}{} & \(-\)2.36 & \(<\)0.0001 & \(-\)3.34 & \(<\)0.0001 & \(-\)3.32 & \(<\)0.0001 & \(-\)4.28 & \(<\)0.0001 \\ \multicolumn{1}{c}{} & \(-\)2.50 & \(<\)0.0001 & \(-\)3.27 & \(<\)0.0001 & \(-\)3.46 & \(<\)0.0001 & \(-\)4.50 & \(<\)0.0001 \\ \multicolumn{1}{c}{} & \(-\)0.02 & 0.4395 & \(-\)0.05 & 0.2688 & \(-\)0.19 & \(<\)0.0001 & \(-\)0.16 & 0.0030 \\ \multicolumn{1}{c}{} & 0.01 & 0.8295 & 0.11 & 0.1040 & 0.17 & 0.0034 & 0.17 & 0.0246 \\ \hline \end{tabular}
\end{table} 
Table 3: The regression analysis of the associations of change of exercise status over 4- and 8 years, MNA score and number of diseases with ADL and IADL scores in 2003 and 2007 *. and disability and exhibited slower progression of ADL/IADL disability [3]. A meta-analysis for randomized controlled trials has indicated the significantly beneficial impacts of physical activity on ADL performance in old age [6]. Older adults who were aged more than 65 years and attended a physical activity program maintained their functional ability in the intervention period without extra use of health care resources [5].