physical inactivity is the fourth leading risk factor of mortality.1 for inactive older adults ( 65 years old ) , a prescribed volume of physical activity2 might be a barrier to long - term adherence .
gardening is an especially feasible leisure time activity in taiwan because plants grow all year round in its tropical marine climate .
however , on this island with its high population density , most households do not have land and gardeners usually manage houseplants by themselves at or near their homes ( figure 1 ) .
it is thus of interest to examine whether home gardening without much physical exertion yields a beneficial effect on survival similar to that reported for the danish diet , cancer and health cohort,3 a new haven elderly cohort,4 and a finnish cohort in 1980.5 it is also possible that there are some reservations about the benefits , as in the whitehall ii cohort study.6 home gardeners are usually more solitary than community gardeners.7 although gardening as a leisure activity or a versatile therapeutic medium has a long history , its temporal health effects might not be directly evidenced by cross - sectional data that reflect a person s current health condition .
therefore , we considered temporality and used time - dependent covariates to construct our survival models .
mobility limitations and comorbidities easily interrupt and stop leisure gardening ; we examined these covariates as either cross - sectional or time - dependent . because indoor plants8 and gardening9 seem to psychologically and physically benefit many people
, we examined whether self - reported depression interfered with the potential temporal health effects of gardening in our survival models .
the present study , which followed - up a national representative cohort 50 years old , and which was linked to taiwan s national mortality registry , examined the long - term effects of gardening on all - cause mortality .
we used time - dependent models to examine , after adjusting for current mobility , depression , comorbidities , and some baseline potential confounders , whether leisure gardening had any long - term effect on all - cause mortality .
the study was approved by the human experiment and ethics committee of national cheng kung university hospital ( heec no : /b - er-101 - 041 ) .
the taiwan longitudinal study on aging ( tlsa ) has conducted seven waves of surveys on a nationally representative sample of late - middle - aged and older adults since 1989 .
the tlsa used a three - stage probability sampling method based on the national household register .
remote mountainous aboriginal townships were excluded . trained interviewers home - visited the cohort and conducted a structured interview in each wave .
the response rate has been ~90% in six of the seven surveys.10 the present study used the data from the last four surveys ( 1996 , 1999 , 2003 , and 2007 ) .
a proxy would be interviewed whenever a participant was unable to be interviewed due to any physical or mental conditions .
subjective questions , for example , on depression or cognitive tasks , could not be answered by proxy and were thus coded with specific missing codes .
we tried different ways of imputation in the sensitivity analysis to test the robustness of our final inferences , for which all subjects were included .
the participants were first asked if they grew flowers , gardened , or cultivated potted plants for pleasure .
if they said yes , then they were asked how often they did this : 1 ) less than once a month , 2 ) two to three times a month , 3 ) once or twice a week , or 4 ) almost daily .
the end - point was either the year the participant died , based on the national mortality registry until december 31 , 2007 , or the censored year of the last interview or of the emigration registry .
mortality and mobility limitations among the older adults are highly associated with major illnesses , and the present study thus includes six comorbidities that are common among old people : diabetes , hypertension and heart disease , stroke , cancer , lung disease , and kidney disease . 
mobility limited  was defined as  requiring aids or another person , or having difficulty doing any of the following eight tasks alone .  to compare the differences between gardeners and nongardeners at baseline , mobility limitations were classified as follows : a  mild mobility limitation  was defined as having difficulty squatting , lifting an 11 kg weight , or running 2030 m ; a  moderate mobility limitation  as having difficulty standing for 15 minutes , walking 200300 m , or climbing up two to three floors ; and a  severe mobility limitation  as having difficulty raising one s arms up or grasping with one s fingers.11 self - reported depressive symptoms were assessed using the ten - item version of the center for epidemiologic studies depression scale , and a summed score ( range : 030 ) > 10 was coded as 
depressed mood.12,13 the demographic factors include age , sex , with or without a domestic partner , and employment . because socioeconomic status ( ses ) might confound the relationship between gardening and mortality , four items were identified as ses proxies : education , residence , employment , and satisfaction with current economic status .
many old people in taiwan did not receive a formal education , and participants with a higher level of education might have a better chance of achieving a better ses .
years of education are categorized as < 7 ( primary school ) , 712 ( secondary school : junior and senior high school ) , and > 12 ( tertiary school : junior college and above ) .
residence is categorized as city ( urban ) , town ( suburban ) , and countryside .
therefore , satisfaction with current economic status , which did not have so many missing values , is used as the fourth ses proxy . according to the self - reported levels of satisfaction on a 5-point likert scale ,
three important health behaviors that might be related to mortality and gardening were included : smoking , drinking , and exercise .
the first two were binary : current smokers and alcohol drinkers , regardless of frequency and amount , were coded positive .
the third was categorized by weekly frequency : 5 times / week = infrequent exercisers , and 6 times / week = regular exercisers .
any difficulty in six instrumental activities of daily living ( iadls),14,15 including shopping for groceries , ability to handle finances , mode of transportation , heavy housekeeping , such as cleaning windows or the ditches surrounding the house , light housekeeping , such as sweeping floor or washing dishes , and ability to use a telephone , was coded as  iadl impaired . 
the potential confounders  demographics , ses , health behaviors , comorbidities , mobility , and depression  were stepwise included in the models .
we also examined the mortality hazards of gardening in the full models stratified by mobility limitations and depression at baseline .
time - dependent values of three groups of variables  six comorbidities , mobility limitations , and depression  were the last available values in the four surveys used as our dataset .
sensitivity analyses were conducted to examine the effects of missing values . there were 4,501 participants with no missing values for baseline variables of interest , but there were 414 participants without valid center for epidemiologic studies depression scale-10 and 385 who did not report whether they were satisfied with their current economic status .
the participants with missing values appeared to be significantly older , less active , and more depressed , and to have less education , more comorbidities , and more mobility limitations at baseline .
because any missing value from a participant would impede the contribution of the other available information , we used three different imputation methods .
the first was  last value carried forward  to impute the missing values of the time - dependent covariates : any missing value before a participant was censored or deceased was imputed using the last available value from the previous surveys .
the second was to impute the in - between missing values by averaging two near ends , and using last value carried forward if the missing values were from the last available survey .
the study was approved by the human experiment and ethics committee of national cheng kung university hospital ( heec no : /b - er-101 - 041 ) .
the taiwan longitudinal study on aging ( tlsa ) has conducted seven waves of surveys on a nationally representative sample of late - middle - aged and older adults since 1989 .
the tlsa used a three - stage probability sampling method based on the national household register .
remote mountainous aboriginal townships were excluded . trained interviewers home - visited the cohort and conducted a structured interview in each wave .
the response rate has been ~90% in six of the seven surveys.10 the present study used the data from the last four surveys ( 1996 , 1999 , 2003 , and 2007 ) .
a proxy would be interviewed whenever a participant was unable to be interviewed due to any physical or mental conditions .
subjective questions , for example , on depression or cognitive tasks , could not be answered by proxy and were thus coded with specific missing codes .
we tried different ways of imputation in the sensitivity analysis to test the robustness of our final inferences , for which all subjects were included .
the participants were first asked if they grew flowers , gardened , or cultivated potted plants for pleasure .
if they said yes , then they were asked how often they did this : 1 ) less than once a month , 2 ) two to three times a month , 3 ) once or twice a week , or 4 ) almost daily .
the end - point was either the year the participant died , based on the national mortality registry until december 31 , 2007 , or the censored year of the last interview or of the emigration registry .
mortality and mobility limitations among the older adults are highly associated with major illnesses , and the present study thus includes six comorbidities that are common among old people : diabetes , hypertension and heart disease , stroke , cancer , lung disease , and kidney disease . 
mobility limited  was defined as  requiring aids or another person , or having difficulty doing any of the following eight tasks alone .  to compare the differences between gardeners and nongardeners at baseline , mobility limitations were classified as follows : a  mild mobility limitation  was defined as having difficulty squatting , lifting an 11 kg weight , or running 2030 m ; a  moderate mobility limitation  as having difficulty standing for 15 minutes , walking 200300 m , or climbing up two to three floors ; and a  severe mobility limitation  as having difficulty raising one s arms up or grasping with one s fingers.11 self - reported depressive symptoms were assessed using the ten - item version of the center for epidemiologic studies depression scale , and a summed score ( range : 030 ) > 10 was coded as 
depressed mood.12,13 the demographic factors include age , sex , with or without a domestic partner , and employment . because socioeconomic status ( ses ) might confound the relationship between gardening and mortality , four items were identified as ses proxies : education , residence , employment , and satisfaction with current economic status .
many old people in taiwan did not receive a formal education , and participants with a higher level of education might have a better chance of achieving a better ses .
years of education are categorized as < 7 ( primary school ) , 712 ( secondary school : junior and senior high school ) , and > 12 ( tertiary school : junior college and above ) .
residence is categorized as city ( urban ) , town ( suburban ) , and countryside .
therefore , satisfaction with current economic status , which did not have so many missing values , is used as the fourth ses proxy . according to the self - reported levels of satisfaction on a 5-point likert scale ,
three important health behaviors that might be related to mortality and gardening were included : smoking , drinking , and exercise .
the first two were binary : current smokers and alcohol drinkers , regardless of frequency and amount , were coded positive .
the third was categorized by weekly frequency : 5 times / week = infrequent exercisers , and 6 times / week = regular exercisers .
any difficulty in six instrumental activities of daily living ( iadls),14,15 including shopping for groceries , ability to handle finances , mode of transportation , heavy housekeeping , such as cleaning windows or the ditches surrounding the house , light housekeeping , such as sweeping floor or washing dishes , and ability to use a telephone , was coded as  iadl impaired . 
the participants were first asked if they grew flowers , gardened , or cultivated potted plants for pleasure .
if they said yes , then they were asked how often they did this : 1 ) less than once a month , 2 ) two to three times a month , 3 ) once or twice a week , or 4 ) almost daily .
the end - point was either the year the participant died , based on the national mortality registry until december 31 , 2007 , or the censored year of the last interview or of the emigration registry .
mortality and mobility limitations among the older adults are highly associated with major illnesses , and the present study thus includes six comorbidities that are common among old people : diabetes , hypertension and heart disease , stroke , cancer , lung disease , and kidney disease . 
mobility limited  was defined as  requiring aids or another person , or having difficulty doing any of the following eight tasks alone .  to compare the differences between gardeners and nongardeners at baseline , mobility limitations were classified as follows : a  mild mobility limitation  was defined as having difficulty squatting , lifting an 11 kg weight , or running 2030 m ; a  moderate mobility limitation  as having difficulty standing for 15 minutes , walking 200300 m , or climbing up two to three floors ; and a  severe mobility limitation  as having difficulty raising one s arms up or grasping with one s fingers.11 self - reported depressive symptoms were assessed using the ten - item version of the center for epidemiologic studies depression scale , and a summed score ( range : 030 ) > 10 was coded as 
the demographic factors include age , sex , with or without a domestic partner , and employment . because socioeconomic status ( ses ) might confound the relationship between gardening and mortality , four items were identified as ses proxies : education , residence , employment , and satisfaction with current economic status .
many old people in taiwan did not receive a formal education , and participants with a higher level of education might have a better chance of achieving a better ses .
years of education are categorized as < 7 ( primary school ) , 712 ( secondary school : junior and senior high school ) , and > 12 ( tertiary school : junior college and above ) .
residence is categorized as city ( urban ) , town ( suburban ) , and countryside .
therefore , satisfaction with current economic status , which did not have so many missing values , is used as the fourth ses proxy . according to the self - reported levels of satisfaction on a 5-point likert scale
three important health behaviors that might be related to mortality and gardening were included : smoking , drinking , and exercise .
the first two were binary : current smokers and alcohol drinkers , regardless of frequency and amount , were coded positive .
the third was categorized by weekly frequency : 5 times / week = infrequent exercisers , and 6 times / week = regular exercisers .
any difficulty in six instrumental activities of daily living ( iadls),14,15 including shopping for groceries , ability to handle finances , mode of transportation , heavy housekeeping , such as cleaning windows or the ditches surrounding the house , light housekeeping , such as sweeping floor or washing dishes , and ability to use a telephone , was coded as  iadl impaired . 
the potential confounders  demographics , ses , health behaviors , comorbidities , mobility , and depression  were stepwise included in the models .
we also examined the mortality hazards of gardening in the full models stratified by mobility limitations and depression at baseline .
time - dependent values of three groups of variables  six comorbidities , mobility limitations , and depression  were the last available values in the four surveys used as our dataset .
sensitivity analyses were conducted to examine the effects of missing values . there were 4,501 participants with no missing values for baseline variables of interest , but there were 414 participants without valid center for epidemiologic studies depression scale-10 and 385 who did not report whether they were satisfied with their current economic status .
the participants with missing values appeared to be significantly older , less active , and more depressed , and to have less education , more comorbidities , and more mobility limitations at baseline .
because any missing value from a participant would impede the contribution of the other available information , we used three different imputation methods .
the first was  last value carried forward  to impute the missing values of the time - dependent covariates : any missing value before a participant was censored or deceased was imputed using the last available value from the previous surveys .
the second was to impute the in - between missing values by averaging two near ends , and using last value carried forward if the missing values were from the last available survey .
we analyzed 5,058 participants : 1,029 ( 20.3% ) daily gardeners , 3,547 ( 70.1% ) nongardeners , and the rest with in - between gardening frequencies ( male : 53.4% ; mean age : 66.69.4 years ; with at least one of the six comorbidities : 1,557 [ 30.9% ] ) .
daily gardeners had lower mortality and were more educated and urbanized , less satisfied with their income , and healthier than their nongardener counterparts at baseline ( tables 1 and s1 for gardeners with in - between frequencies ) .
of 1,783 participants who reported themselves as daily gardeners , 895 ( 50.2% ) remained as daily gardeners in another survey .
daily home gardening at baseline was associated with better survival when only age , sex , and with or without a domestic partner had been adjusted for ( hazard ratio [ hr ] : 0.67 ; 95% confidence interval [ ci ] : 0.590.76 ) or when all baseline covariates had been adjusted for ( hr : 0.82 ; ci : 0.710.94 in model f ) ( table 2 ) .
no dose effect of different gardening frequencies was found ( tables s2 and s3 ) .
the hr seemed to stabilize once demographics , ses , iadl , and health behaviors had been adjusted for in the models ( table 2 ) , despite the potential direct effects of comorbidities , mobility limitations , and depression on mortality .
the protective effect of daily gardening at baseline decreased for those with later comorbidities , mobility limitations , and depression ( hr : 0.87 ; ci : 0.731.02 in model t-4 ) ( table 3 ) . to clarify the effects of mobility and depression
, we also stratified the participants by mobility limitations and self - reported depression at baseline .
the positive effect of daily gardening was robust among those with any mobility limitation and without depression at baseline , but not among those without a mobility limitation or with depression ( table 2 ) . for those who had chronic mobility limitations but
no depression at baseline , baseline daily gardening appeared to be significantly beneficial for survival ( hr : 0.64 ; ci : 0.480.87 in model t-5 ) ( table 3 ) after time - dependent comorbidities , mobility , depression ( table 3 ) , and cognitive function ( table s4 ) had been adjusted for .
however , the conferred protection level fell for participants with mobility limitations who had relapsed or chronic depression ( model t-5 ) ( table 3 ) . for those who reported any iadl impairment at baseline ( n=1,415 )
, our exploratory analyses yielded a protective effect of daily gardening ( hr : 0.58 ; ci : 0.430.79 ) adjusted for covariates and three sets of time - dependent variables , regardless of cognitive condition ( table s5 ) . for those who had neither depression nor a mobility limitation at baseline
the sensitivity analyses showed a consistent protective effect of gardening , regardless of the method used to impute missing values ( table 4 ) , namely , the results of reduced mortality among daily gardeners might be under - estimated because of the exclusion of missing values .
we found that , for people > 50 years old with mobility limitations , daily home gardening as a leisure - time activity seems to postpone ~36% of mortality .
it is noteworthy that this protection did not apply to people without mobility limitations at baseline ( model g in table 2 and model t-5 in table 3 ) .
the positive effects of light - intensity and solitary gardening on survival appear to have some therapeutic component in addition to their preventative effect .
we can not completely rule out that daily gardeners with mobility limitations have less severe health conditions at baseline than do nongardeners .
therefore , we reported only the results in fully adjusted models so that we would not overestimate the effects of gardening . additionally , our finding that daily gardening reduced the risk of mortality by ~18% in the older general population ( model f in table 2 ) is similar to that reported in two danish studies.3,16 for those individuals with mobility limitations , possibly caused by aging or morbidities , daily gardening for pleasure may increase longevity .
gardening in many western countries might involve something akin to yardwork , because the garden is usually large and the activity involves a great deal of walking and other yard - related exercise ( eg , mowing or raking the lawn ) , especially of the legs and arms .
gardening in taiwan , however , more frequently means growing plants in flowerpots or other improvised containers ( eg , plastic beverage bottles ) on the sunporch or in front of the door in urban and suburban areas ( figure 1 ) . because taiwan is densely populated ( 648 persons / km ) and because two - thirds of the land on its main island is occupied by high mountains , relatively few households can afford an outdoor garden .
our flowerpot gardening activities , such as pruning and watering , require mostly low - intensity upper - body movement ( metabolic equivalents <3 in korean older adults);17 in contrast , having an outdoor vegetable or flower garden as a leisure activity , which requires moderate - intensity upper- and lower - body movement,18 is less common in taiwan . in our study ,
a mobility limitation means requiring aids ( eg , a walker , a cane , or a wheelchair ) or another person , or having difficulty doing any of the following eight tasks alone : squatting , lifting an 11 kg weight , running 2030 m , standing for 15 minutes , walking 200300 m , climbing up two to three floors , raising one s arms up , and grasping with one s fingers . five of these tasks involve mostly the lower body .
elderly gardeners who have difficulty running 2030 m may add to their life expectancy by engaging in the upper body movements required to transplant and water potted plants .
gardening for more than an hour per week was associated with fast gait speed and good performance in the semitandem and full - tandem balance tests among 3,237 american old adults.19 compared with other more strenuous physical activities , for example , walking and cycling , home gardening is possible for people with mobility limitations .
in contrast , elderly gardeners without any mobility limitations would be less likely to gain additional years of survival from the low - energy exercise provided by home gardening .
daily gardening  for pleasure  implies that motivation might explain some of the protective effects of gardening .
a survey of 126 visitors to a garden center on their attitudes toward gardening found that appreciation for nature and concerns for other people were the main benefits of gardening.20 another mail survey of 303 volunteers from a university aging and cognition lab used a motivation questionnaire for leisure in general , and reported seven motivational factors for gardening : 1 ) intellectual , 2 ) stimulus - avoidance , 3 ) friendship building , 4 ) social interaction , 5 ) physical fitness , 6 ) skill - development , and 7 ) creativity.21 because home gardening involves neither large - scale outdoor gardens nor another person , we were unable to differentiate whether there were motivations involving the outdoor natural environment,22 friendship , or economic factors,23 and it may be that these are not applicable in urban or suburban taiwan .
nonetheless , motivations relevant to plants , intrapersonal emotions , cognition , and physical skills and abilities might contribute to gardening for pleasure . additionally , leisure participation and physical activities in older adults are often a continuation of what these individuals used to do in the first half of their lives.2426 however , health conditions26 and a lack of interest in the activities seemed to be common obstacles to continuity of such actions,25 and previous participation was a consistent predictor.24 while only 50% continued their home gardening in this 11-year follow - up , in comparison to an 8-year follow - up of 380 canadian older adults , 67.5% of whom continued their outdoor yardwork,26 engagement in pleasurable voluntary activity seemed to confer survival advantages .
nature affects health through four proposed pathways : air quality , social cohesion , physical activity , and stress reduction,22 and daily home gardening seems most likely to be on the physical activity ( despite its low intensity ) and stress reduction pathways .
however , we found that gardening had no effect at all for people with depression but without a mobility limitation , although it was helpful to people with a mobility limitation and with no comorbid depression . the reciprocal relation between depression and brain dysfunction might facilitate a pervasive negative impact,30 including disability and mortality.31 depression deteriorates health , mentally and physically , and chronic or relapsed self - reported depression seemed to weaken the benefits of home gardening for survival .
home gardening in taiwan probably has little or no protective effect against all - cause mortality in the older adults with depression , possibly because the intensity of such activity is low and it may offer relatively limited psychological benefits .
first , no details of gardening other than frequency were available in the tlsa dataset .
we thus were unable to create other relevant models or to make any recommendations for the duration , intensity , body movement , and psychological elements of gardening , other than frequency .
however , frequent nonexercise physical activities ( performing home repairs ; cutting a lawn , hedge , and so on ; car maintenance ; taking bicycle rides , skiing , ice - skating , going hunting or fishing ; and gathering mushrooms or berries ) were shown to reduce mortality in sweden.32 while this study may have clarified how home gardening works among an older taiwanese population , we were unable to generalize to other leisure activities with similar potential mechanism .
second , because of the limited sample size , we were unable to stratify the results by morbidities or various degrees of mobility limitations to examine the effects of gardening in more detail .
third , despite the preliminary protective effect of daily gardening among those with iadl impairments at baseline , the disablement process of dementia might be different , and further research with a larger sample size would validate and shed light on our exploratory findings .
although the above mechanisms are still open to additional studies , home gardening might be an easy - to - start and sustainable leisure activity worth recommending to older adults , particularly those who have mobility limitations .
the entry - level investment for home gardening is low : a container and a plant .
moreover , there is an abundance of aids and tools for older adults who are wheelchair - bound or who have other mobility limitations , and thus gardening as a leisure activity can easily be prolonged despite limitations that might interrupt other physical and social activities .
however , additional research is needed to explore whether the social interactions and outdoor psychological advantages of gardening in an allotment ( ie , working in a community garden primarily for growing vegetables : http://www.allotment-garden.org/ ) or large private garden confer significantly more protection than tending to small , inside - the - house flowerpot  gardens  against chronic depression on mortality .
in this 11-year follow - up nationwide study , daily gardening was consistently shown to reduce mortality after the confounding factors of age , sex , ses , health behaviors and condition , and time - dependent illness conditions , and even using different methods to impute missing values , were adjusted for .
daily home gardening was particularly protective of survival for people with baseline mobility limitations but without depression .
it may thus be worthwhile to recommend gardening to middle - aged and older adults as a daily activity , although additional investigations of the physical and psychological effects of gardening are needed .
baseline demographic and physical characteristics of participants in 1996 stratified by 5-frequency gardening number deceased / number total .
all data are presented as frequencies ( percentage ) , except for follow - up time , age , and education which are presented as mean ( standard deviation ) .
iadl : any difficulty in shopping for groceries , ability to handle finances , mode of transportation , heavy housekeeping , light housekeeping , and ability to use a telephone .
mild mobility limitation : any difficulty in squatting , lifting an 11 kg weight , or running 2030 m ; moderate mobility limitation : any difficulty standing for 15 minutes , walking 200300 m , or climbing up two to three floors ; severe mobility limitation : raising one s arms up or grasping with one s fingers.1 measured using the cesd-10 scale ( range : 030 ; cutoff : 10).2 abbreviations : cesd-10 , center for epidemiologic studies depression 10 ; iadl , instrumental activities of daily living ; n , number .
hr and 95% ci of baseline 5-frequency gardening on all - cause mortality and each model mutually adjusted for covariates at baseline note : models a  g were stepwise adjusted for potential confounders .
abbreviations : ci , confidence interval ; hr , hazard ratio ; iadl , instrumental activities of daily living .
hr and 95% ci of baseline 5-frequency gardening on all - cause mortalitya adjusted for time - dependent covariates all models adjusted for socioeconomic status ( age , sex , with or without a domestic partner , education , employment , residence , income satisfaction ) , health behaviors ( smoking , drinking , exercising ) , and iadl at baseline ; and time - dependent comorbidities , mobility limitations , and depression at baseline if not modeled as time - dependent variables .
abbreviations : ci , confidence interval ; hr , hazard ratio ; iadl , instrumental activities of daily living .
hr and 95% ci of baseline 5-frequency gardening on all - cause mortality among participants who had limited mobility and no depression at baseline ( n=1,145 ) iadl : any difficulty in shopping for groceries , ability to handle finances , mode of transportation , heavy housekeeping , light housekeeping , and ability to use a telephone .
mild mobility limitation : any difficulty in squatting , lifting an 11 kg weight , or running 2030 m ; moderate mobility limitation : any difficulty standing for 15 minutes , walking 200300 m , or climbing up two to three floors ; severe mobility limitation : raising one s arms up or grasping with one s fingers.1 measured using the cesd-10 scale ( range : 030 ; cutoff : 10).2,3 immediate recall of ten items modified from rey auditory verbal learning test,4 and of one task from digits backward test.5 abbreviations : cesd-10 , center for epidemiologic studies depression 10 ; ci , confidence interval ; hr , hazard ratio ; iadl , instrumental activities of daily living .
hr and 95% ci of baseline 5-frequency gardening on all - cause mortality adjusted for time - dependent covariates among people with iadl impairmentsa in 1996 ( n=1,415 ) iadl , any difficulty in shopping for groceries , ability to handle finances , mode of transportation , heavy housekeeping , light housekeeping , and ability to use a telephone .
mild mobility limitation , any difficulty in squatting , lifting an 11 kg weight , or running 2030 m ; moderate mobility limitation , any difficulty standing for 15 minutes , walking 200300 m , or climbing up two to three floors ; severe mobility limitation , raising one s arms up or grasping with one s fingers.1 measured using the cesd-10 scale ( range : 030 ; cutoff : 10).2,3 immediate recall of ten items modified from rey auditory verbal learning test,4 and of one task from digits backward test.5 abbreviations : ci , confidence interval ; cesd-10 , center for epidemiologic studies depression 10 ; hr , hazard ratio ; iadl , instrumental activities of daily living .
 aimsto test the hypothesis that gardening is beneficial for survival after taking time - dependent comorbidities , mobility , and depression into account in a longitudinal middle - aged ( 5064 years ) and older ( 65 years ) cohort in taiwan.methodsthe cohort contained 5,058 nationally sampled adults 50 years old from the taiwan longitudinal study on aging ( 19962007 ) . 
 gardening was defined as growing flowers , gardening , or cultivating potted plants for pleasure with five different frequencies . 
 we calculated hazard ratios for the mortality risks of gardening and adjusted the analysis for socioeconomic status , health behaviors and conditions , depression , mobility limitations , and comorbidities . 
 survival models also examined time - dependent effects and risks in each stratum contingent upon baseline mobility and depression . 
 sensitivity analyses used imputation methods for missing values.resultsdaily home gardening was associated with a high survival rate ( hazard ratio : 0.82 ; 95% confidence interval : 0.710.94 ) . 
 the benefits were robust for those with mobility limitations , but without depression at baseline ( hazard ratio : 0.64 , 95% confidence interval : 0.480.87 ) when adjusted for time - dependent comorbidities , mobility limitations , and depression . 
 chronic or relapsed depression weakened the protection of gardening . for those without mobility limitations and 
 not depressed at baseline , gardening had no effect . 
 sensitivity analyses using different imputation methods yielded similar results and corroborated the hypothesis.conclusiondaily gardening for pleasure was associated with reduced mortality for taiwanese > 50 years old with mobility limitations but without depression . 
Introduction
Methods
Participants
Measurements
Gardening and mortality
Comorbidities, mobility, and depression
Demographics and SES
Health behaviors and conditions
Statistical analysis
Results
Discussion
Conclusion
Supplementary materials