How do I add a time-variable parameter into my ODE model?

I'm new to MATLAB and I have been stuck on this problem for a while now. I'd really appreciate if you help me solve this small problem.

I am trying to solve a mathemical model defined by a system of ODE. The ODE is given below as follows.

I've coded the above system as follows:

IC = [300;0;1;0;300;0;0];

tspan = [0 5000];
[t, Y] = ode45(@odefun, tspan, IC);

function DYdt = odefun(t, Y)
    % Y is 7x1 vector
    
    Sh = Y(1);
    Eh = Y(2);
    Ih = Y(3);
    Rh = Y(4);
    Sm = Y(5);
    Em = Y(6);
    Im = Y(7);
    
    a = 0.25;
    b = 0.04;
    c = 1/14;
    d = 0.205;
    f = 0.415;
    g = 1/12;
    h = 1/365;
    j = 1/365;
    l = 0.4/365;
    Lambdah = 0.028;
    muh = 0.0000391;
    alphah = 0.0004;
    Lambdam = 6;
    mum = 0.04;
    alpham = 0.01;
    ITN = 0.5;
    IRS = 0.5;
    LLIN = 0;
    
    
    dShdt = -a*Im*Sh*(1-ITN-LLIN)/(Sh+Eh+Ih+Rh)+b*Rh+Lambdah-muh*Sh;
    dEhdt = a*Im*Sh*(1-ITN-LLIN)/(Sh+Eh+Ih+Rh)-c*Eh-muh*Eh;
    dIhdt = c*Eh-d*Ih-muh*Ih-alphah*Ih;
    dRhdt = d*Ih-b*Rh-muh*Rh;
    dSmdt = -f*Ih*Sm*(1-ITN-LLIN)/(Sm+Em+Im)+Lambdam-mum*Sm-h*ITN*Sm-l*LLIN*Sm-j*IRS*Sm;
    dEmdt = f*Ih*Sm*(1-ITN-LLIN)/(Sm+Em+Im)-g*Em-mum*Em-h*ITN*Em-l*LLIN*Em-j*IRS*Em;
    dImdt = g*Em-mum*Im-alpham*Im-h*ITN*Im-l*LLIN*Im-j*IRS*Im;
    
    DYdt = [dShdt; dEhdt; dIhdt; dRhdt; dSmdt; dEmdt; dImdt];
end

NOW, I would like to change some of the parameters from constants to variables that change with time. In this example, the parameter h lineraly degrades over the entire time span. I tried doing this by adding the following code:

h = (1/365)*(1-(t/5000));

But, I see NO change when I run this model, and get the same exact graphs as before. How do integrate this into my model, so that I can have linearly degrading variables in my model?

Thank you so, so much in advance! I would deeply appreciate the assistance. Please do try and help me out!